Class 8

AP State Syllabus AP Board 8th Class Biology Important Questions Chapter 9 Production and Management of Food From Animals

AP State Syllabus 8th Class Biology Important Questions 9th Lesson Production and Management of Food From Animals

8th Class Biology 9th Lesson Production and Management of Food From Animals 1 Mark Important Questions and Answers

Question 1.
From where do we obtain food?
Answer:
We obtain food from plants and animals.

Question 2.
What are the food items that are obtained from animals?
Answer:
We obtain milk, meat and eggs from animals.

Question 3.
What is animal husbandry?
Answer:
Providing food, shelter, protection and breeding of animals is called animal husbandry.

Question 4.
How did man use animals since long time?
Answer:
Since long time, man used animals not only for obtaining food but also for agriculture, transportation etc.

Question 5.
Why did early man domesticate only some of the animals?
Answer:
The early man domesticated only some of the animals which provide him food, clothing and the animals which are helpful for agriculture and transportation.

Question 6.
In what way the animals are useful to us?
Answer:
Buffalo and cow give us milk, hens give us eggs and meat, goats and sheep provide us meat, ox, bulls, donkeys are useful for agriculture and transportation.

Question 7.
What do farmers believe in our country?
Answer:
In our country farmers believe that animal husbandry is part and parcel of agriculture.

Question 8.
Name the animals that domesticate by the people living in rural areas.
Answer:
People living in rural areas domesticate animals like cows, buffaloes, bullocks, goats, sheep, pigs, hens, etc.

Question 9.
What is the important issue in Animal husbandry?
Answer:
Supplying of nutritious food, accommodating clear and hygienic shelters for animals is important issue in animal husbandry.

Question 10.
Where do people rear their cattle in the village?
Answer:
Generally villagers send their cattle to rear at the places where grass is easily available.

Question 11.
Where do farmers keep their cattle?
Answer:
Farmers keep their cattle in the sheds.

Question 12.
Name the agricultural practices done by using bullocks and he-buffaloes.
Answer:
Ploughing and levelling the field farmers use bullocks and he-buffaloes.

Question 13.
How do cattle rearers protect their cattle?
Answer:
Cattle rearers make fences in the fields at off crop seasons.

Question 14.
How is the milk production effected?
Answer:
Milk production is effected by viral and bacterial diseases.

Question 15.
In rainy season how are cattle protected from mosquitoes?
Answer:
Cattle can be protected by covering mosquito nets.

Question 16.
Who will provide treatment and health care for cattle?
Answer:
Veterinary doctor will provide treatment and health care for cattle.

Question 17.
Name the dangerous disease in cows and buffaloes.
Answer:
Galikuntu is a common and dangerous disease in cows and buffaloes.

Question 18.
From which disease sheep and goats will suffer?
Answer:
Sheep and goats will suffer from worm infections (Nattala Vyadhi)

Question 19.
How do our government treats milk production?
Answer:
Our Government treats milk production as an industry.

Question 20.
How much milk is given by traditional species of cows?
Answer:
2 to 5 litres of milk per day.

Question 21.
How much milk is given by murra species?
Answer:
Murra species give up to 8 litres of milk per day.

Question 22.
Name the traditional varieties of cows.
Answer:
Haryana, Jaferabad, Nagapuri are the traditional varieties which give good quantity of milk.

Question 23.
Name the foreign varieties of cows.
Answer:
Jersy (England) and Holstein (Denmark).

Question 24.
What is the milk yield from foreign varieties?
Answer:
They give 8 to 20 litres of milk.

Question 25.
What is pasteurization?
Answer:
The destruction of disease producing organisms present in the milk. In this process milk is heated at 62° temperature and cooled below 10°C.

Question 26.
In which months milk production is high?
Answer:
In the months of October and November milk production is high.

Question 27.
Who is the father of white revolution?
Answer:
Prof. J.K. Korian is the father of white revolution in India.

Question 28.
How is milk secreted?
Answer:
Milk is secreted from the mammary glands of animals.

Question 29.
Why do people in our country decorate their cattle during festivals?
Answer:
People believe that cattle are part and parcel of our culture. They treat them as their family members. So they decorate their cattle.

Question 30.
Why do some persons collect bones of dead animals?
Answer:
because bones are used in fertilizer industry.

Question 31.
What is the use of leather of animals?
Answer:
Leather of cattle is used in the leather industry.

Question 32.
What is Biogas? How is it produced?
Answer:
Biogas is produced from the wastes from cattle, home etc. As this is produced biologically, this gas is called biogas used for domestic purposes.

Question 33.
What are Broilers and layers?
Answer:
Broilers are the hens reared for meat and layers are the hens reared for eggs in poultry.

Question 34.
Name some local variety of poultry varieties.
Answer:
Aseel, Kadaknath, Chittagang, Longshan, Bursa are the pure local varieties.

Question 35.
What is a poultry?
Answer:
Production and rearing of hens on a large scale is called poultry.

Question 36.
In which place India is occupied in production of eggs?
Answer:
India achieved 4th position in the world by producing 41.06 million eggs per annum.

Question 37.
Name the foreign varieties of hens giving meat.
Answer:
New Hampshire, White plymouth, Rhode island red, while leg horn and Anoka.

Question 38.
What are the major practices in food production?
Answer:
Animal husbandry, poultry, fish culture, bee culture etc., are the major practices in food production.

Question 39.
In which months the egg prices are high?
Answer:
During January to April, egg prices are high.

Question 40.
Why egg prices are more in January to April?
Answer:
This is because of most of the eggs are used for hatching.

Question 41.
What is the temperature for hatchability of eggs?
Answer:
Hatchability of eggs is generally influenced by 37°C to 38°C temperature.

Question 42.
Write a slogan on nutritional Egg.
Answer:
“If you want to be healthy person eat egg every day”.

Question 43.
Name the traditional variety meant for fighting.
Answer:
Aseel (Berisa Kodi) is the Indian traditional variety meant for fighting.

Question 44.
How is hatching done in our rural areas?
Answer:
Our rural areas, the practitioner hatch eggs by placing them under broody hen.

Question 45.
What is the weight of Emu bird?
Answer:
The weight of Emu bird is nearly 50 kg.

Question 46.
What is the life span of natural wild varieties?
Answer:
Natural wild varieties grow fully in 5 to 6 years.

Question 47.
What is the life span of broilers?
Answer:
Broilers grow fully in just 6 to 8 weeks.

Question 48.
What is Apiculture?
Answer:
Culture of honey bees (apis) is called Apiculture.

Question 49.
What is the use of honey bee production?
Answer:
Development of apiculture is not only for honey production but also very much useful for crop pollination.

Question 50.
Which insects are the best pollinators?
Answer:
Honey bees are the best pollinators of many agricultural crops.

Question 51.
How much honey is produced by Indian honey bee?
Answer:
Indian honey bee produces 3 – 10 kg of honey.

Question 52.
Which honey bee is produces more honey?
Answer:
European honey bee produces 25 – 30 kgs of honey per annum.

Question 53.
Name the honey bees present in honey bee colony.
Answer:
A honey bee colony consists of one queen bee, several thousands of workers and few hundreds of drones.

Question 54.
What is the primary function of a queen bee?
Answer:
The primary function of a queen bee is to lay eggs.

Question 55.
What is the life span of a queen bee?
Answer:
The life span of queen bee is two-three years.

Question 56.
What are worker bees?
Answer:
The sterile females are called worker bees in the hive.

Question 57.
What is the function of worker bees?
Answer:
They attend to indoor duties during first three weeks of their lives such as secretion of royal jelly feeding of the brood, collecting nectar, pollen and water.

Question 58.
Name the plants that are sources of nectar.
Answer:
Fruit trees like citrus, apple, guava, tamarind, cultivated fields, crops like mustard, gingelly, wheat, cotton, sunflower.

Question 59.
What are the other products of Apiculture?
Answer:
Bee venom and bee wax are the other products of Apiculture.

Question 60.
How is bee venom used?
Answer:
Bee venom is used for the preparation of “Apistincture” used in homeopathic treatment.

Question 61.
What are the uses of bee wax?
Answer:
The uses of bee wax are production of polish cream, nail polish etc.

Question 62.
Name the parts present in a artificial bee hive.
Answer:
It consists of floor board, brood chamber, super chamber, top cover, inner cover, frames and entrance rod.

Question 63.
Name the pests and predators that attack honey bee colonies.
Answer:
Wax moths, wasps, rubber flies, dragon flies attack honey colonies. King crow, Bee eater are more harmful.

Question 64.
How are fish important for us?
Answer:
Fish constitute an important and rich sources of high quality animal protein.

Question 65.
What are the inland water areas?
Answer:
Rivers, fresh water and brackish water lakes, reservoirs, tanks, ponds, swamps etc., are the inland water areas.

Question 66.
Name the crustacean fishery.
Answer:
Prawns, lobsters and crabs together constitute the crustacean fishery.

Question 67.
Name the local varieties offish.
Answer:
Murrel (Korramenu), Katla (jalla), Katrana (bochalu), rohu (mosu), seer (vanjram) are the local varieties.

Question 68.
Name the marine fish varieties.
Answer:
Macerel, tuna, saradines are the marine fish varieties.

Question 69.
What are mechanized fishing?
Answer:
Fishermen catch fish by using machines is called mechanized fishing.

Question 70.
Name some marine fishes which are of high economic value.
Answer:
Mullets, Bhetki and peral spots, shel fishes such as prawns mussels and oysters as well as sea weed.

Question 71.
What are estuaries?
Answer:
Brackish water resources where sea water and fresh water mix together are called estuaries.

Question 72.
What is the reason for growing fish in paddy fields?
Answer:
The reason for this is increasing use of inorganic fertilizers and insecticides in paddy fields.

8th Class Biology 9th Lesson Production and Management of Food From Animals 2 Marks Important Questions and Answers

Question 1.
How do you appreciate the role of poultry to meet the food needs of the present day increasing population ?
Answer:

1. The world is facing the problem of over growth in population.
2. To meet the increasing population food needs, poultry is the best suitable option.
3. So billion hens are reared world wide for eggs and chicken.
4. India achieved 4th position in the world by producing 41.06 million eggs per annum.
5. India is placed in 5th position in the production of 1000 million kgs of chicken per year.
6. Hence, I appreciate the poultry, in fulfilling the food needs of the society.

Question 2.
“Fish has high nutrition values” said Shravya. Do you support Shravya? Why?
Answer:

1. The meat of fish contains 15-25% of proteins. Hence they are the rich sources of proteins.
2. The meat of fish has vitamins like A and D.
3. Fishes are the sources for very important fatty acids and unsaturated fatty acids which are very vital in our body’s metabolic activities.
4. Meat of fish can be easily digested. It helps in the growth and development.

Question 3.
Name the three Indian Major fresh water crops grown in fish culture.
Answer:

1. Rohu – Labeo rohita:
2. Boche – Catla catla
3. Erramosu – Cirrhinus mrigala are the three Indian major crop fishes.

8th Class Biology 9th Lesson Production and Management of Food From Animals 4 Marks Important Questions and Answers

Question 1.
This fish is called Tuna. Collect information about availability catching and marketing of this particular fish.

Answer:
Availability:
English: Big eye Tuna
Latin: Thunnus obesus
size + weight: Average today about 40 -180 c.m. about 1, 4-130 Kg.
Biggest Angled Fish: 197, 3 kg, 236 cm, Peru, 1957 Russel Lee
Maturity: Size 105 cm, weight 25 Kg., age 3 – 4 years
Maximum: Size 230 c.m., Weight 210 Kg., Age 15 years
Catching: 21% Eastern Pacific
38% Western Pacific
22% Indian Ocean
19% Atlantic Ocean
Catching Methods: Longlining, Purse seining and pole-and-line (by-catch)
Share of all Tuna: 2011 about 10% – 398.000 m.t
Main Production: Thailand, Philippines, Indonesia, Mexico, Venezuela, Ecuador, Colombia, Spain, Italy.
Life cyle: About 7-8
Major Markets: Japan (Sashimi)
Populr Product: Fresh (Whole fish)
Forms: Fresh Fillets (Sashimi)

Question 2.
Write a note on different methods used to store the fish in your area.
Answer:

1. The fish caught should be preserved in chilled conditions.
2. After catching the fish, gut is removed. Before transportation, fishes are thoroughly washed in clean and chlorinated waters.
3. They are perceived in insulated ice boxes with alternate layers of crushed ice and fishes in 1 : 1 proportion.
4. Preservation can also be done by
   a) Drying b) Salting c) Smoking d) Canning methods
5. Before canning, harmful bacteria like clostridum botulinum must be destroyed.
6. Cold storage facility and vans with refrigerated chamber have improved the storage and transport of fish.

Question 3.
Visit a poultry farm of your village. Collect the diseases of poultry and their preventive control measures. Prepare them in theform of a table.
Answer:

Question 4.
Write some diseases of tamed animals.
Answer:

1. Galikuntu is a common and dangerous diseases occur in cows and buffaloes.
2. Sheep and goats suffer from worm infections (Nattala vyadhi).
3. Some parasitic diseases cause damage to liver and intestine of tamed animals.
4. Viral and bacterial diseases also effect on milk production of cows and buffaloes.
   These are some examples for diseases in domestic animals.

8th Class Biology 9th Lesson Production and Management of Food From Animals Important Questions and Answers

Question 1.
How are the microorganisms like bacteria killed and how can the milk be preserved at milk chilling centres?
Answer:

1. Pasteurization of milk ensures the destruction of disease producing organisms present in milk.
2. In this process, milk is heated at 72°C for 30 minutes.
3. Prior to this, the milk was being cooled to below 10°C.
4. This process was invented by Louis Pasteur.

Question 2.
Dung is used as biofuel. You know that it is an accessory product. Write about such accessory products produced in animal husbandry.
Answer:
1. The supplimentary products produced from animal husbandry are meat, dung, leather, bones, horns, etc,
2. Animal husbandry is also contributing to different industries like

1. Dairy industry: Milk and milk products are produced.
2. Slaughter houses: Production of meat.
3. Leather industry: Tanning of leather and making shoes, belts and suitcases, etc.
4. Fertilizer industry : Bones of cattle are used in the production of chemical fertilizers.
5. Bio gas industry: Cattle dung is used in the production of biogas.
6. Toys industry: The horns of cattle are used to make toys and ornamental items.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 6 Sound Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 6th Lesson Sound

8th Class Physical Science 6th Lesson Sound Textbook Questions and Answers

Improve Your Learning

Question 1.
Fill in the blanks with suitable words.
a) The to and fro motion of a body from its mean position is called ……… .
b) Number of vibrations per second is called ………. .
c) The intensity of sound can be measured in ……… .
d) Sound cannot travel in ………. .
e) Vibrating bodies produce ………. .
f) The maximum displacement of a body from its mean position is called ……… .
Answer:
a) vibration
b) frequency
c) Decibel
d) vacuum
e) sound
f) amplitude

Question 2.
A normal human being can listen to sounds with frequency from …….. to ……. vibrations per sec.
Answer:
20, 20000

Question 3.
How will you differentiate the amplitude and frequency of different sounds? Give two suitable examples from your daily life.
Answer:
The pitch of a sound depends upon sound whereas intensity of sound depends upon amplitude.
If we are hearing a loud sound that means it has greater amplitude.
If we are hearing a feeble sound that means it has least amplitude.
If the shrillness of sound is less then the frequency of the sound is less.
If the shrillness of sound is more then the frequency of the sound is more.
Examples for daily life:
Frequency:

1. The shrillness of adult women is more than adult men because of greater frequency associated with vocal cords.
2. The different sounds produced by whistle and drum are due to difference in frequencies.
3. Amplitude:
   1. The difference in sound produced by lawnmower and car horn due to difference in their amplitude.
   2. The sound produced by crackers during Diwali is due to greater amplitude.

Question 4.
Write any three musical instruments that you know and explain how they produce sound? (OR)
Write any four musical instruments known to you and explain how do they produce sound.
Answer:
The three musical instruments are:

1. Veena: This instrument contain strings of different thickness fixed on hollow wooden boards, with different tensions. When a string of certain thickness fixed under certain tension is vibrated which changing vibrating lengths different sounds are produced.
2. Mridangam: It is in cylindrical shape and it containing membranes fixed with different tensions on the two sides. When it is vibrated by hand or by sticks at different places produce different sounds.
3. Flute: It has a cylindrical tube open at both ends. It is provided with holes in a row on its surface. By blowing air through it, while changing the length of air column, different sounds are produced.

Question 5.
The sounds of crickets (insects) make us close our ears. Why?
Answer:
The sounds of crickets are shrill creaking which make us to close our ears.

Question 6.
Robert observed a musical instrument producing sound. But he didn’t find any vibration of any part of that instrument. This observation raised many questions in his mind. Can you guess what are the questions raised in his mind? Write them.
(OR)
Latha observed a musical instrument producing sound. But she did not find any vibration of any part of that instrument. This observation raised many questions in her mind. Guess the questions raised in her mind and write any two of them.
Answer:

1. How does the instrument produce sound?
2. Whether an object produce sound without any vibration?
3. If it is producing vibration why do we unable to felt it?
4. Does sound has energy?

Question 7.
“Vibrations in a body produce sounds”. How do you prove it?
Answer:
Put a hack-saw blade in between a table and brick as shown in figure and press it and leave it abruptly. It produces sound and we observe hack-saw blade is vibrating. Which proves a vibrating body produces sound.

Question 8.
Can parrots speak? Discuss with your Mends and collect information.
Answer:
Yes, parrots can speak. But parrot do not have vocal cords, so sound is accomplished by expelling air across the mouth of the bifurcated trachea. Different sounds are produced by changing the depth and shape of trachea. So talking or speaking of parrots are really whistling in different variation. Parrots speak without understanding words.

Question 9.
Collect the photographs of local musicians and exhibit them in your class.
Answer:

Question 10.
Collect photographs showing various situations of sound pollution and prepare a scrap book.
Answer:

Question 11.
Zakir said “vibrations produce sound. And sound produces vibrations. This is how we hear every sound”. Establish that the given statement is true with relevant examples from your surroundings.
Answer:
Examples for vibrations produce sound :

1. Fix a rubber band tightly on an empty match box. Pluck the rubber band and keeping it near to our ear we can hear sound that shows vibrating object produce sound.
2. A vibrating hack-saw blade placed between a table and brick produces sound. Which is also an example for vibrating body produces sound.

Examples for sound produces vibration:

1. Sound produced by supersonic planes vibrates the wall of buildings and glass windows due to which we can observe the cracks on the walls or breakage of windows.
2. Take a cell phone and playing music with high volume in a plastic bottle. Close the mouth of bottle with a balloon using rubber band and place sugar crystals above the bottle. We can observe the vibrations of sugar crystals.

Question 12.
Make different musical instruments using local available materials and exhibit them in your class.
Answer:

1. Jalatarang: Take 4 to 5 metal or glass bowls or tumblers. Fill them with water in increasing order. Strike gently each bowl or tumbler with a spoon. We can produce different musical sounds. So it acts as Jalatarang.
2. Two note flute: Get a jug or bottle. Cut a smaller than finger sized hole in the bottom of the bottle / jug. Blow across the hole that is already in the top of the jug/ bottle until you get a clear note. Cover and uncover the hole on the bottom with your finger. You can also try tilting your head down and up to make the note sharp or flat.
3. Drum: Get a plastic paint barrel. Put it on the ground between your feet or in the crook of your elbow. Play it like a drum.
4. Guitar: Take empty shoe box and cut a circle in the middle. Cut six rubber bands so that they can be stretched out to their full length. Press brass fastners into the shoe box placing six on the top and six on the bottom of the box. Stretch out the rubber band, one at time, tying them onto the fastners. Cut a paper roll in half and slide in underneath the rubber bands below the hole. Which will act as guitar.

Question 13.
Explain why we are not able to hear the explosions taking place in the sun.
Answer:
Sound wave cannot travel in vacuum (meaning space). In order to hear sound waves it must required medium. So we are not able to hear explosions happening in the sun.

Question 14.
Write any two slogans to reduce sound pollution.
Answer:
Slogans to reduce sound pollution:

1. The more you make noise. The faster you lose your voice.
2. Noise an evil. You help doing it, it gives you a reward making you a deaf.

Question 15.
Write your suggestions about reducing sound pollution.
Answer:

1. Attach silencers to bikes and other machines to reduce sounds.
2. Manufacture machines that work with less noise.
3. During the use of TV and taperecorder tune down volume of sound.
4. Plant trees to reduce sound pollution.
5. Community laws must. Silence zones near school/colleges, hospitals, etc.
6. Noise producing industries, airports, bus and transport terminals and railway stations to sighted far from living places.

Question 16.
How does sound pollution effects bio – diversity? Explain.
Answer:
Slogans to reduce sound pollution:

1. The more you make noise. The faster you lose your voice.
2. Noise an evil. You help doing it, it gives you a reward making you a deaf.

Effects of sound pollution on bio-diversity:

1. The first harmful effect is loss of hearing.
2. It also leads to several health related problems, e.g: Sleeplessness, hypertension, increase in blood pressure, etc.
3. It effects the mental health of people.
4. In animals, noise can increase the risk of death by altering predator or prey detection and avoidance, interfere with reproduction and navigation and contribute to permanent hearing loss.
5. Noise pollution causes poor quality of crops.
6. Under water animals such as whales and dolphins too experience discomfort due to noise pollution caused by submarines, shipping companies and sonars. Cuttle fish and octopus suffer serious damage from noise pollution.

8th Class Physical Science 6th Lesson Sound InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 86

Question 1.
What is the effect of humidity on quality of sound propagation? Is there any difference in propagation of sound in air during the summer and winter seasons? Discuss with your Mends.
Answer:
With increase in humidity, density of air decreases. So with rise in humidity velocity of sound increases.
This is why sound travels in humid air (rainy season or winter) than in dry air (summer) at the same temperature.

8th Class Physical Science Textbook Page No. 87

Question 2.
“Vibrations produce sound and sound produces vibrations”. Which is true in this? Discuss.
Answer:
Yes, it is true. We already know a vibrating object produce sound. Sound is a mechanical wave that can produce vibration. (Mechanical waves have ability to vibrate an object)

Question 3.
“Our ear has the three media through which sound propagates.” Discuss with your Mends as to whether the above statement is true.
Answer:
Yes, it propagates through three media. The first media is external ear, the second media is middle ear, the last media is inner ear.

8th Class Physical Science 6th Lesson Sound Activities

Activity – 1

Question 1.
Listening to sound and predicting its source:
Let us sit quietly for a while and listen to sounds of objects, animals. Prepare a list of sounds that we hear and the sources from which they might have originated. Write them in the table.
Answer:

Activity – 2

Question 2.
Identifying different sounds:
Make a student to stand at the blackboard such that his face is turned towards the blackboard and ask other student in the class to make different sounds. The student at the board should tabulate the sounds he heard and sources of those sounds as shown in the table.

a) How does the student at the blackboard guess the source of sound without actually seeing the source?
Answer:
Student has identified the variations in sound by listening.

b) How do objects produce sound?
Answer:
When we vibrating the objects, they produce sound.

c) What happens when objects made of metals are hit by a hammer or fall down from a height on a concrete floor ?
Answer:
When objects made of metals are hit by hammer from a height, they produce sound.

d) How does a flute or a whistle produce sound?
Answer:
Vibration of air column produce sound in flute or whistle.

e) How would you feel if you touch a body while it is producing sound?
Answer:
My body is vibrating when I touch a body (or object) while it is producing sound.

Activity – 3

Question 3.
Vibrating body produces sound:
Take a brass bell (bell used in Pooja room or in your school).
Ring the bell and listen to the sound carefully. Now hold the bell tightly with your hand as shown in figure and ring it again.

a) Do you hear sound from the bell ?
Answer:
Yes, but slightly.

b) Is there any change in the sound produced in the two situations?
Answer:
Yes, in the second case the sound is feeble.

c) What do your hands feel when bell is ringing?
Answer:
The hand vibrates.

d) Remove your hand and ring it again. Do you hear a different sound? Why?
Answer:
Due to the vibrations are transmitted to hand and bell is not properly vibrating so it produces a feeble sound. Once the hand is removed bell rings properly and sound become louder and different.
Let us do following activities:

e) Fix a rubber band tightly on an empty matchbox. Pluck the rubber band and keep it close to your ear. Do you hear any sound? Do you feel any vibration in your hands?
Answer:
Yes, I heard a sound. I felt the vibration.

f) Blow air into papers of your notebook. What happens? Does the action produce any sound? Do you find any vibrations in the note book?
(OR)
If you blow air into papers of your notebook, sound will be produced. Write your observation in this activity.
Answer:
Yes, it produce sound and I found vibrations in the notebook.

g) Fill a plate with water and let the water settle. Strike the rim of the plate with a spoon as shown in figure. What do you observe? What do you hear? Where do you find vibrations in this case?

Answer:
I heard a sound. The vibrations are found in plate as well as in water.

h) Put a hack-saw blade in between a table and a brick as shown in the figure and press it and leave it abruptly. What happens? Does it produce sound? What is the state of the hacksaw blade while it is producing sound?

Answer:
Yes, it produces sound. The blade is vibrating.

i) What have you observed while doing the above activities?
Answer:
All of them produced sound.

j) What changes took place in those objects?
Answer:
These objects are vibrate while producing sound.
But there are certain instruments which producing sound though we cannot see any vibrations in the instruments like in flute and clarinet etc.

k) How do they produce sound?
Answer:
They are producing sound due to vibration of air column.

l) Is it possible to produces sound without vibration?
Answer:
No, it is not possible to produce sound without vibration.

m) Does every vibrating body produce sound?
Answer:
Yes, every vibrating body produce sound.

n) Does sound has energy?
Answer:
Yes, sound has energy.

Activity – 4

Question 4.
Sound has energy: (OR)
Suggest an activity to prove “sound has energy”.
Take a plastic bottle and a cell phone. Cut the top of the bottle so that it looks like a glass. Play songs on the mobile phone in high volume and place it in the bottle. Close the mouth of bottle with a balloon using rubber band so that it covers the bottle as shown in the figure and stretch it tightly so as to behave like a diaphragm. Place some sugar crystals or small size of sand particles on the balloon diaphragm and observe the movement of particles. Do the same activity after removing the phone from the bottle.

a) What do you notice?
Answer:
When there is no cell phone inside the bottle, sand particles on diaphragm remain stationary. While the cell phone playing songs inside the bottle, the diaphragm vibrates which can be seen through dancing of sand particles. The sound produced by cell phone inside the bottle is responsible for these vibrations. Thus sound has energy to make sand particles vibrate on the diaphragm.
Musical instruments:
You might have observed many musical instruments like Tabala, Flute, Harmonium and Guitar. The sounds produced by these instruments are distinct. It is easy for us to identify which sound is coming from which instrument.

b) How do they produce sound?
Answer:
They produce sound due to vibration.

c) Why there is a difference between the sounds produced by various musical instruments?
Answer:
The mode of vibration is different.

d) Which part of these instruments is responsible for production of sound?
Answer:
Different parts for different instruments:

e) Can you name the instrument for which more than one part is responsible for the production of sound?
Answer:
Tabala, Mridangam.

f) How do you compare the production of sound in a flute and sound produced in a water tap when it is turned on, just before the water flows out of it.
Answer:
Both are same process. They produce sounds due to vibrating air columns.

Activity – 5

Question 5.
Producing a sound that resembles sound of rainfall:
Start clapping with fore finger on left hand palm, add the middle finger and clap again, then ring finger and lastly small finger successively and reverse the process gradually. If all the students in your class do it simultaneously the sounds produced would resemble the on set and stopping of rainfall.

Activity – 6

Question 6.
Observing the changes in sound:
Take 4 or 5 metal glass bowls or tumblers. Fill them with water in decreasing order. Strike gently each bowl or tumbler with a spoon.

a) What do you hear?
Answer:
We can hear a musical sound. This is a jalatarang.
Fill the bowls or tumblers with equal amounts of water, strike each ball like in above case and listen the sound.

b) What difference do you notice in the sound produced?
Answer:
It does not produce musical note in this case.

c) Why is there variation in the sound produced due to change in the water level of a bowl?
Answer:
The change is due to change in air columns. That is sounds are produced by the vibrating bodies and air passes through orifices of the instrument.

Activity – 7

Question 7.
Observing the movements of vocal cords during speech :
Ask a friend to raise his neck up. Stretch a chocolate wrapper across his mouth and ask him to blow air on the wrapper forcibly. Observe the changes in movement at his throat. Ask him to blow again slowly and observe the difference in movements.
a) What changes do you observe in the movements at the throat on the two occasions?
Answer:
During the first trial the voice box gets tensed and produces high sound while during the second trial it is close to normal position of throat and produces lower sound. The sound produced in the above activity is due to a combination of vibrations produced in the wrapper and the vocal cord.
Propagation of sound:
Sound needs a medium to propagate:
The sound produced by the school bell will be heard by all of us irrespective of whether we are in a room opposite to the bell or in a room at the back of the bell. Obviously, the sound produced by the school bell travels in all directions and reaches us, propagating through the air present between source of the sound and our ears. That is the air surrounding us act as a medium which allows the sound to pass through it.

b) Does sound travel only in air?
Answer:
No, it will travel in other media.

c) Does it travel in any other gaseous medium?
Answer:
Yes, it will travel in any other gaseous medium.

d) Does sound also travel in other media like solids and liquids?
Answer:
Yes, it will travel.

Activity – 8

Question 8.
Observing sound propagation in solids:
Strike one end of the table with a pen and ask your friend to listen to the sound produced keeping her ear touching the table at other end and also ask her to listen to the sound by lifting her head slightly from the table. Ask your friend what difference she noticed while hearing the sounds when her ears were away from the table and touching the table.

Take a metal or wooden strip. Strike it at one end and ask your friend to hear the sound by keeping his ears at the other end of the strip. Ask your friend what difference he noticed while hearing the sounds when his ears are away from the strip and touching the strip.

a) Do you know how to make a toy telephone using tea cups?
Answer:
Take two paper-cups. Make small holes at the bottom of these cups. The holes should be very small so that only a thin string can pass through them. Take a long string. Make sure that the string does not have any knots in it. Push the string through the hole in one of the cups. Fix the string by putting a knot at the end. Similarly fix the string to the other cup. Our phone is ready.

You and your friend can communicate with this phone now. Stand away from each other so that the string is tightly held. One of you can speak in the cup while the other can listen by putting the cup on his ear.

b) Are you able to hear the sound?
Answer:
Yes, we can hear the sound.

c) What is a medium between you and your Mend which is responsible for propagation of sound?
Answer:
The medium is thread.
In the above activities you observed that sound travels in solid medium like wood, metal, thread, etc.

Activity – 9

Question 9.
Propagation of sound through liquids:
Take a bucket fill it with water. Take two stones and strike them against each other keeping your hands inside the water. Ask your friend to listen to the sound by keeping his / her ears touching walls of the bucket.

Ask your friend about the difference between sounds produced by striking the stones against each other in water and striking them in air.
Thus the conclusion is that sound propagates through matter in all the three states – solid, liquid and gas.
a) Does sound travel in liquids?
Answer:
Yes, sound can travel in liquids.

b) Can we hear the sound produced in water?
Answer:
Yes, we can hear.

Activity – 10

Question 10.
Does the sound travel if there is no medium?
Take a water tumbler or a glass made of plastic or glass. Make sure that the tumbler or the glass is dry. It should be long enough to accommodate a cell phone vertically. Place a cell phone small in size in the glass and play the ring tone of the mobile. Listen to the ringtone and its volume level. Cover the glass with a small plate and again listen to the ringtone and note the difference in volume of the sound.

Now suck the air from the glass keeping it close to your mouth. If you suck air quickly the rim of the glass will stick around your mouth due to air lock. Listen to the volume of the ringtone at this stage. And also ask your friend to listen to the sound for comparing variation in its volume.
a) Is there any change in the volume of sound observed by you or your Mend?
Answer:
When the tumbler is covered with a plate, the volume reduces but you can hear the ringtone. As we start sucking more and more we can notice that the volume decreases gradually. If the air is sucked completely, you will not hear the sound at all. But practically it is not so easy.
This activity gives an idea about need of a medium for propagation of sound.

Lab Activity – 1

Question 11.
Conduct an experiment to know the relationship between the intensity of sound produced by a body and the vibration of the body.
Answer:
Aim: To know the relation between the intensity of sound produced by a body and the vibrations of the body.
Materials required: Wooden table, 30 cm metal scale or nearly 30 cm hack-saw blade and a brick.
Procedure:
Place the blade/scale on the table, with 10cm of the blade on the surface of the table and rest of it in air. Keep a heavy brick on one end of the 10 cm blade/ scale kept on table.

Vibrate the blade gently and observe the vibrations and simultaneously listen to the sounds. Repeat the same 2-3 times and record observations in the table shown below.
Vibrate the blade using greater force. Observe the vibrations and listen to the sound. Repeat this for 2-3 times and record your observations in the table shown below.

a) When do you hear a loud sound?
Answer:
When we applied large force we heard a loud sound.

b) When do you hear a feeble sound?
Answer:
When we applied less force we heard a feeble sound.

c) What difference do you notice in vibrations of blade / scale during loud and feeble sounds?
Answer:
During loud sound the amplitude of vibration is more and for feeble sound the amplitude is less.

d) What difference do you find in amplitude of vibration for a feeble and a loud sound in the above experiment?
Answer:
For a loud sound the amplitude is more and for a feeble sound the amplitude is less.

Lab Activity – 2

Question 12.
Explain identification of pitch or shrillness of sound with the help of an activity.
(OR)
What are the characteristics of sound? Explain the procedure to identity the pitch of sound.
Answer:
Chardcteristics sound are 1) Loudness 2) Pitch 3) Quality.
Aim: Identifying pitch or shrillness of a sound.
Materials required: A wooden table, two hack-saw blades or metal scales of 30cm length and a brick.
Procedure:
Place the first blade/scale on the table, with 10cm portion of the blade on the table and rest of it in air. Keep a brick as weight on the 10 cm portion of the blade/scale kept on the table. Vibrations of hack-saw blades
Place the second blade/scale on the table (see that the gap between these two blades is 10cm), with 25cm on the table and 5cm in air. Keep a brick as weight on the scale/blade.

Vibrate both blades with same force. Observe the vibrations and listen to the sounds produced.
Repeat the same 2-3 times and record observations in the table showed below.

a) What difference do you notice in number of vibrations of two blades?
Answer: The number of vibrations in 5 cm blade is more.

b) What difference do you notice in the quality of sound produced by them?
Answer:
The sound produced by 5 cm blade is more shrill when compared to that of 20 cm blade.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 12 Stars and the Solar System Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 12th Lesson Stars and the Solar System

8th Class Physical Science 12th Lesson Stars and the Solar System Textbook Questions and Answers

Improve Your Learning

Question 1.
What is your local noon time?
Answer:
The time when the shortest shadow of a vertical object occurs in a particular place is called local noon time at that place.

Question 2.
Where do you find moon at night?
a) 2 days before Poumami
b) 2 days after Amavasya
Answer:
a) Couple of days (2 days) before full moon day (Pournami), a crescent is seen in the west just after sunset.
b) Couple of days (2 days) after the new moon day (Amavasya), a crescent is seen in the west just after sunset.

Question 3.
Why doesn’t eclipse occur on every full moon day or on every new moon day?
Answer:
Lunar eclipse can happen during a full moon and only when the moon and earth and sun are directly in line and the moon passes through the earth shadow. Most of the time the moon is slightly out of line and that is why we don’t have a Lunar eclipse every full moon.

Question 4.
Where do you find the pole star?
Answer:
The pole star lies on the line joining the two outer stars of the constellation great bear. Pole star directly above the north pole of earth.

Question 5.
What Is the difference that you find between pole star and other stars?
Answer:
If we observe the position of various stars constantly. We will notice that they are not in a fixed position because as the earth rotates about a fixed axis, the position of stars with respect to earth changes. But the position of pole star does not change with respect to earth.

Question 6.
Why does polestar seem to be stationary?
Answer:
The polestar is situated in the direction of the earth’s axis and that is why it does not appear to move even though all stars appear that they are moving because of ie rotation of earth. So pole star seems to be stationary.

Question 7.
Name some constellations.
Answer:
Names of some constellations:

1. Great bear (Saptarishi)
2. Cassiopeia (Sharmistha)
3. Orion
4. Leo (Simha)
5. Corona
6. Borealis

Question 8.
How many planets are there in our solar system? What are they?
Answer:
There are 8 planets in our solar system. They are:

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus and
8. Neptune.

Question 9.
Look at the below table and name the smallest and the biggest planets in our solar system.

Answer:
From the table the biggest planet is Jupiter and the smallest planet is Mercury.

Question 10.
Among all 8 planets what is the special thing about earth?
Answer:
The special thing about earth is it is the only planet in the solar system on which life is exist.

Question 11.
How do day and night occur?
Answer:
The day and night occur due to rotatory motion of earth.

Question 12.
Do the stars appear moving? How can you say?
Answer:
Yes, stars are appear moving. Our galaxy like all other spiral galaxies is rotating. The stars move on orbits around the centre of the galaxy. It was the motions of stars in external galaxies that lead to the idea of dark matter in the universe. Stars also have some random motions. They do not orbit galaxy in exact circles. As observers we see this motion of the stars as what is called proper motion, the projection of their velocity on to the plane of the sky is radial motion.
Normal Answer : Alternate answer is No. All the stars appears that they are moving because of rotation of earth.

Question 13.
Is it possible to see the polestar for the people who live in the southern hemisphere of the earth? Why?
Answer:
A pole star is a visible, preferably a prominent one, that is approximately aligned with the earth’s axis of rotation. The term polestar refers to polaris which is the current northern pole star also known as the north star. So the people in southern hemisphere unable to see this pole star.

Question 14.
What is the use of artificial satellites in our daily life?
Answer:
Artificial satellites have many uses in daily life.

1. They are used for forecasting weather.
2. They are used for transmitting television and. radio signals.
3. They are also used for telecommunication.
4. They are used in aviation and military (these satellites are called remote sensing which will collect information from a distance).

Question 15.
Why is Venus the brightest planet?
Answer:
Venus is very bright that’s partly because sunlight easily reflected by acidic clouds that blanket the planet atmosphere and also it is closest planet to earth.

Question 16.
Are you curious about going to the moon? Why?
Answer:
Yes, I am curious about going to moon. Because I want to find answers raised in my mind.

1. Is it true there is no life on moon?
2. If it does not have atmosphere, how it look like?
3. How earth look like from moon?
4. Whether there are any mountains on moon or not?
5. There may be any creators on moon or not?
6. Whether there is any form of water exists on moon?
7. Whether we able to walk on moon as freely as on earth surface?

Question 17.
While observing the shadow of a stick from morning to evening, some questions arose in Ramya’s mind. What may be those questions?
Answer:

1. Why sun is changing its position from morning to evening?
2. How does the length of the shadow change with time?
3. Why we are getting longest shadows in the morning and evening?
4. Why the shadow in the noon is shortest?
5. Do all the days at noon have same size of shadow?

Question 18.
What are the questions that engage your mind when you look at night sky?
Answer:

1. Is stars collide with each other?
2. Where does the stars go in the morning?
3. Whether stars daily travel in the same path?
4. Why night sky is black and early morning sky is blue?
5. Whether we can count stars in the sky?
6. Why stars grouped to form constellations?

Question 19.
Even though we do not have clock, we can know the time by observing some shadows in daytime. Think and discuss with your friends how we can know the time at night?
Answer:
We can know the time by position of moon and stars or with reference to pole star. Estimation of time by using position of moon:

1. If the moon is full do the experiment stop if it is new moon.
2. Imagine the moon is divided into 12 vertical strips. First hour at right edge and last hour at left edge. It can vary by season or location.
3. Read the moon from left to right following an imaginary horizontal half line.
   Look for where the line intersects the boarder between light and dark. Make a note of which strip that intersection is in.

For example:
The instruction is at 8 pm and transition from right to left is from light to dark. This tells us the moon will set in the west at 8 pm.
This moon will set at about 7-8 hours after sunset. If sunset is at 8 pm. You can expect moon time is at 3-4 am.

Question 20.
How can you find north – south direction at your place?
Answer:
This experiment should be performed on a day when the sky is clear, preferably between nine in the morning and four in the evening.

Pick a spot in open ground away from buildings and trees. The spot should be as flat as possible.
Take a stick which is a little over a meter long and fix it vertically in the ground. Ensure that exactly one meter of stick remains above the surface of ground. Build a fence around your stick as shown in figure.
Make your first observation at nine in the morning, Make a mark with a nail or peg at the point where the tip of the shadow falls on ground. Measure the length of the shadow.
Then, make similar observations for every half an hour throughout the day till four in the evening.
Find the direction of shortest shadow cast by vertical object on the ground. That gives the north-south direction.

Question 21.
In which direction (towards north or south) is the sun moving day by day when you read this lesson?
Answer:
From December 21 to till June 21 the sun appears to shift northward. From June 21 to December 21 the sun appears to shift southward.
(Basing on this information we have to give the answer suppose you have read the lesson in the month of February the sun is moving towards north direction).

Question 22.
What are the planets you have seen in the sky? When do you observe those planets?
Answer:
The two planets observe in the sky are

1. Venus: Sometimes Venus appears in the eastern sky before sunrise. Sometimes it appears in the western sky just after sunset. Therefore it is often called a morning or an evening star.
2. Mars: It appears slightly reddish and therefore, it is also called red planet. It appears in the east.

Question 23.
What is the duration of a day and night today? Collect the information about duration of day and night for the past 7 days from the newspapers, analyze it and say whether summer or winter is going to come.
Answer:
Students have to collect the information from newspaper and other resources.
(Hint: If sun is shifting towards south the upcoming season is winter if it is shifting towards north the upcoming season is summer).

Question 24.
What are the other districts on the same latitude as your district ?
Answer:
I am residing at Krishna district. The latitudes of Krishna district are 16. The other districts which have same latitude are West Godavari, Mahaboobnagar.
(You should write the latitude of your district and you have to find out the districts which lie in that latitude from table -1 on page 163 of textbook.)

Question 25.
Collect the information about cosmic dust (wastage) from newspapers, internet and make a poster on your school panel board about the consequences of cosmic dust.
Answer:
Cosmic dust: Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 mm in size.
Consequence of cosmic dust:
The orbit of space junk could deteriate resulting in the junk falling to earth. If it survives and reaches the earth’s surface it would cause the same damage as equally sized meteorite, including damaging or destroying structures in the area killing people, etc.
The earth receives hundreds of tonnes of space dust, rocks, etc every week. If you were to get whole load of it in one place and try and breathe it in it probably would be harmful. However natural concentrations are so low that it possess no risk.

Question 26.
Make a sundial. Explain how you made it.
Answer:
Making of sundial:
Cut a right angled triangle ABC from a sheet of cardboard. Angle C of the triangle should equal to the latitude of your city or town and angle A should be 90° as shown in figure.

Fix cardboard triangle vertically in the middle of a rectangular wooden board. Glue strips of paper along both edges of BC and the wooden board to make the triangle stand erect.
Place your board with the triangle on level ground in an open space which gets sunlight throughout the day. Base BC of the triangle should be placed in the north- south direction, with B pointing to the north.
At nine in the morning, draw a line along the shadow of side AC on the wooden board. Write the time along side of the line. Draw lines of the shadow of side AC at one hour intervals through the day till sunset and mark the time for each line. The sundial is now ready.

Question 27.
Draw the different phases of moon. Arrange them in an order from poumami to amavasya.
Answer:

Question 28.
Draw the location of polestar showing the direction from Great Bear.
Answer:

Question 29.
Draw the diagram of the solar system.
Answer:

Question 30.
How do you appreciate the construction of knowledge about the universe by our ancestors?
Answer:
They study of our universe changed from time to time from earth is flat to higgs bosan particles. All these secrets about our universe are revealed due to constant afforts of our ancestors. That is due to construction of knowledge about the universe by our ancestors. So the afforts of our ancestors should be thoroughly appreciated.

Question 31.
We launched so many artificial satellites around our earth for different purposes. What do you think about the impact of artificial satellites and their radiation on bio-diversity?
Answer:
Effect of radiation released from artificial satellites on biodiversity:
I. Animals and humans:

1. Killing certain enzymes in the body can simply make sick.
2. If radiation damages DNA, the body may not repair it. It increases the chances of both animals and humans developing cancer.

II. Marine animals: High level of radiation cause a reduction and reproduction capabilities of marine animals.
III. Plants: Weaking of seeds and frequent mutations. Excess of radiation killing plants.

Question 32.
Among eight planets of our solar system, earth is the only planet supporting life. Explain how we should protect our earth and its environment.
Answer:
Steps to be taken to protect earth and environment:

1. Reduce pollution by reducing air, water and land pollution.
2. Recycle resources by sending the degradable like paper and non degradable like plastic and glass objects to recycling factory.
3. Save resources by using them carefully. E.g.: Water, trees, wood, paper.
4. Stop burning fossil fuels (Coal, oil and natural gas) for that do not waste electricity.
5. Plant lot of trees.

8th Class Physical Science 12th Lesson Stars and the Solar System InText Questions and Answers

8th Class Physical Science Textbook Page No. 160

Question 1.
What are the celestial objects that we can see in the sky?
Answer:
Stars, Planets, Moon (Satellite), Comets, Meteors and Meteorites are the celestial objects that we can see in the sky.

Question 2.
Are the stars moving?
Answer:
Yes, the stars are moving.

Question 3.
Do you see the same stars at night and early in the morning?
Answer:
No, we do not see the same stars at night and early in the morning.

Question 4.
Do you see the same stars during summer and winter nights?
Answer:
Yes, it is due to the change of axis of rotation of the earth.

Question 5.
What is the shape of the moon? Why does it change? Why doesn’t the sun change its shape daily like the moon?
Answer:
The actual shape of the moon is approximately spherical.
But it changes everyday.
The sun does not change its shape like the moon due to its size and the distance it is away from the earth. Moreover the shadow of the earth falls on one side of the moon partially or fully. This makes the changes in its shape. Also the moon does not have its own light to make the shadow of the earth to fall on the huge sun.

Question 6.
Where exactly is the sun situated in the sky at noon?
Answer:
Above our head (vertically above) (Really the sun does not revolve around the earth but due to the rotation and revolution of the earth we feel / imagine that the sun moves around the earth.)

Question 7.
Why does the shadow of a tree change from morning to evening?
Answer:
Due to the rotation of the earth we find the sun at different positions in the sky which brings the tree the different shadows from morning to evening.

8th Class Physical Science Textbook Page No. 168

Question 8.
Will we be able to hear any sound if we were on the moon? Why?
Answer:
Sound required a medium for its propagation. There is no atmosphere (medium) on moon. We know sound cannot travel in vacuum. So we unable to hear any sound if we were on the moon.

Question 9.
Can any life exists on the moon? Why?
Answer:
Moon does not have air (oxygen) and water which are essential for existence of life. So there is no life exists on moon.

8th Class Physical Science Textbook Page No. 169

Question 10.
Why does lunar eclipse occur only on a full moon day?
Answer:
Lunar eclipse occur only on a full moon day because lunar eclipse happen when the earth’s shadow falls on the moon, hiding it from the sun’s light. For this to happen, the moon must be on the opposite side of the earth from the sun. So the full half of the moon that is lit by the sun is visible from earth that is full moon day.

Think and Discuss

8th Class Physical Science Textbook Page No. 161

Question 1.
Look at the nails or pegs you have fixed on the ground to keep track of the shadow of the stick throughout the day. From their positions, can you tell how the position of the sun changes in the sky from sunrise to sunset?
Answer:
The position of sun changes from slanting to vertical and then vertical to slanting.

8th Class Physical Science Textbook Page No. 163

Question 2.
Why does the sun appears to travel towards north or south? Try to find the answer by reading your social studies chapter “Earth movements anti seasons” along with this lesson.
Answer:
The earth’s tilt is constant 23.5 degree perpendicular. The earth position relative to sun changes, not the tilt itself during orbit. The sun is moving towards north throughout summer because the north pole is tilted 23.5 degree towards sun and we are in northern hemisphere. During the winter the south pole is tilted 23.5 degree so the sun appear to travel towards south.

8th Class Physical Science Textbook Page No. 168

Question 3.
Scientists are planning to build settlements on moon and are trying to make arrangements to live there. You know that there is no air on moon. How will it be possible to live on the moon then?
Answer:
Oxygen is essential for humans. Unless we built special structures and buildings on the moon and put oxygen into them, we would not able to live on the moon without wearing oxygen tanks all the time.

8th Class Physical Science Textbook Page No. 178

Question 4.
The diameter of the sun is 13,92,000 Km. The diameter of the earth is 12,756 Km. The diameter of the moon is 3,474 Km. The distance from the sun to earth is 15,00,00,000 Km. The distance from the earth to moon is 3,84,399 Km.
Take the scale as 1 lakh km = 1 cm, and imagine how the arrangement of sun, earth and moon is in our universe. Can you make this arrangement on your school ground?
Answer:
Yes, we can do it in our play ground. Placing sun at the middle. Rotating earth around sun and rotating moon around earth by measuring diameters in cm.

8th Class Physical Science 12th Lesson Stars and the Solar System Activities

Activity – 1

Question 1.
Observing the changes in the length of shadow.
This experiment should be performed on a day when the sky is clear, preferably between nine in the morning and four in the evening.

Pick a spot in the open ground away from trees and buildings.
The spot should be as flat as possible. Take a stick which is a little over a meter long and fix it vertically in the ground. Ensure that exactly one meter of stick remains above the surface of ground.
Make your first observation at nine in the morning. Make a mark with a nail or peg at the point where the tip of the shadow falls on ground. Measure the length of the shadow.
Then, make similar observations for every half an hour throughout the day till four in the evening.
Use a clock to fix the time for making your observations. Enter the measurements of the length of the shadow and the time of measurement in a table making two columns, one for time and another for length of shadow.

(These values are changes from place to place and with seasons)
a) Look at your table and figure out the time of the day of shortest shadow.
Answer:
I observed at 12 noon.

b) When did you observe the longest shadow in your activity?
Answer:
At 4 pm.

c) How does the length of the shadow change with time? Illustrate your answer with the help of some diagrams. Draw the diagrams of the stick and its shadow for 5 different times, that is, at 9am, 1 lam, 12noon, 2pm and 4pm.
Answer:
The size of the shadow decreases and reach a minimum and then increases (It has minimum value at 12 noon)
(Students have to draw the diagrams of the stick and its shadow at 9 am, 11 am, 12 noon, 2 pm and 4 pm by doing this activity)

d) If you continue your activity from sunrise to sunset, at what times do you think the shadow would be the longest?
Answer:
At sunrise and at sunset.

e) Where is the sun situated in the sky at noon? Where does the shadow of stick is fall at that time? Think about how your own shadow will be at that time.
Answer:
Almost in line with the stick. It will falls in north-south direction. My own shadow is also in north-south direction.

f) Do you think that your shadow length will be the same on all the days at noon?
Answer:
Yes, the shadow will be same on all the days (with in two weeks).

g) In which direction does the shortest shadow of the stick fall in your activity?
Answer:
The shortest shadow falls in the north-south direction.
Continue your observations.

h) Observe on the next day whether the shadow of the stick falls at the same spots at the same times throughout the day.
Answer:
Yes, it falls on the same spot.

i) Can you use your stick as a clock (sundial) to tell the time? If your answer is ‘yes’, explain how this is possible.
Answer:
Yes, due to movement of sun from east to west.

j) Two weeks later, once again check to see whether the stick’s shadow falls at the same spots at the same times during the day.
Answer:
It fall on the same spot. But length of shadow change.

k) If the shadow does not fall on the same spot, what could be the possible reason?
Answer:
The position of the sun in the sky changes during the day.

l) If you continue the experiment the position of shadow changes or not ?
Answer:
No, it does not change. The position of sun changes from day to day as well.
That is, the position of the sun at 10.00 am today will be different from its position two weeks later at the same time. If you choose a particular time every week and mark the position of the sun with a peg at that time, you can build a calendar for the full year.

m) During a period of two weeks you had made an observation that the length of the shadow at a particular time is changing day by day. Did it become longer or shorter?
Answer:
Yes, it is changing day by day. During summer it is shorter day by day and during winter it is larger day by day.

n) By observing the direction of shadows, can you guess the arrival of summer or winter?
Answer:
Yes.

Activity – 2

Question 2.
Understanding the north-south movement of the sun.
Fix a spot near your home from where you can observe the sunrise. You may have to go to the terrace of a RCC building or go to an open field for the purpose. Choose a tree or an electric pole or some other stationary object as a reference point.

Over the next 10 to 15 days, note the spot at which the sun rises daily, keeping in mind your reference point. Make a daily sketch of the rising sun as well as your reference point in your notebook during this period.
a) Does the spot of sunrise change? If it does, in which direction does it seem to move?
Answer:
It may moves towards south of the sky if it is Dakshinayanam or it may moves towards north of the sky if it is Uttarayanam.
(So answer based upon Uttarayanam or Dakshinayanam)

b) Was the sun appear travelling towards south or north during the time you made your observations?
Answer:
It is travelling towards north.

c) Do you think that is the reason for the change in the length of the shadow of the stick day by day in activity 1 ?
Answer:
Yes, that is the reason.

d) Assuming that you did not have any calendar and knowledge of months and seasons, can you use movement of the sun to predict the arrival of winter or summer?
Answer:
Yes, if it is moving towards north, the coming season is summer (in the above case it is summer) and if it is moving towards south, the coming season is winter.

Activity – 3

Question 3.
Make your own sundial.
Answer:
First of all, you will need to cut a right angled triangle ABC from a sheet of cardboard. Angle C of the triangle should equal to the latitude of your city or town and angle A should be 90° as shown in figure.

A list of latitudes of districts of Andhra Pradesh is given below in table.

Fix your cardboard triangle vertically in the middle of a rectangular wooden board. Glue strips of paper along both edges of BC and the wooden board to make the triangle stand erect.
Place your board with the triangle on level ground in an open space which gets sunlight throughout the day. Base BC of the triangle should be placed in the north- south direction, with B pointing to the north.
At nine in the morning, draw a line along the shadow of side AC on the wooden board. Write the time along side the line. Draw lines of the shadow of side AC at one hour intervals (use a clock to check the time) through the day till sunset and mark the time for each line. Your sun-dial is ready.

Activity – 4

Question 4.
Observing phases of the moon.
a) Have you ever observed the movement of moon in the sky?
Answer:
Yes.

b) Does the moon appear at same point at a particular time everyday?
Answer:
Yes.

c) s the shape of the moon same on everyday?
Answer:
No, it changes.

Now note the date of the day after new moon day (amavasya), when the moon first appears in the sky.
Also note the time at night when the moon sets (goes down in the western sky). In the same way everyday locate the moon in the sky at the time of sunset or immediately after sunset.
Record the date and time of the moon set and draw a picture of the moon as you see it on that day in your notebook as shown in figure.
Continue making observations for as many nights as possible.
Observe the moon a few days before full moon day (Pournami) to a few days after it. Locate the position of moon in the sky at the time of sunset before Pournami and note the time and position of moon in the sky at that time.
After Pournami, note the time at which the moon rises (comes in the eastern sky) and also note the date. Draw pictures of the shape of the moon each of these days.

d) Can you calculate the number of hours between one moon rise and the next moon rise or the number of hours between one moon setting and the next moon setting, with help of these observations?
Answer:
It is about 24 hours and 50 minutes.

e) How many hours lapse between one sunrise to the next, or one sunset to the next?
Answer:
It is about 24 hours.

f) Is the time period same for sun and moon to appear at selected position after completing a cycle in the sky every day?
Answer:
No, they are different.

g) Does the moon appear at the same point every day during the time of the sunset?
Answer:
No.

h) What is the shape of the moon? Is it same every day?
Answer:
It is changing day by day.

i) You might have observed that the shape of the moon changes night after night. What is the name given to these changes in appearance ?
Answer:
These changes in its appearance are called the phases of the moon.

j) Can you guess why the shape of the moon changes?
Answer:
The time period taken by sun to complete a cycle in the sky and come to the selected position is almost same everyday and it is about 24 hours i.e., 1 day. Whereas moon takes about 50 minutes more than a day to complete the cycle and which results in the phases of moon.

Activity – 5

Question 5.
A Moon-shaped lemon.
Answer:
Choose a day one week after the new moon day when the moon is visible in the sky during the day time.
Take a yellow lemon or a whitewashed clay ball and pivot it on a long needle or on a spoke of bicycle. Hold it up towards the moon as shown in figure.

Ensure that you are standing in the sun¬shine when you do this activity.
Observe the shape formed by the sunlight on the surface of the lemon. Is there some similarity between the shape formed and the shape of the moon?
It forms one of the phase of moon.

Activity – 6

Question 6.
Why does the shape of the moon change ?
(Do this activity around 4p.m.)
Wrap a ball tightly with a white hand-kerchief or with a piece of white cloth.
Assume this is the moon. Hold this ball in front of your eyes in bright sunshine as shown in figure and turn around yourself slowly. Observe how the shape of the illuminated part of the ball changes.

a) Does sunlight fall on half the ball at all times while you turn around?
Answer:
Yes.

b) Is the shape of the illuminated part on the ball viewed by you same in all positions during your rotation?
Answer:
No, they are different.

c) Why does this happen?
Answer:
To understand this look at figure.

c) Why does this happen?
Answer:
To understand this look at figure.

The large circle in the middle of figure is the earth and the smaller circles around it represent the moon in different positions. We can see the phases of the moon on different days in the figure. The sunrays falling on the moon illuminate half its surface in all the positions. However, we cannot see the entire illuminated surface in all the positions. In some cases we see the entire illuminated surface while in others we see only part of it. In one particular position, we cannot see the illuminated surface at all.
The shape of the moon we see is the shape of the illuminated portion visible to us.
In figure, the day of the new moon is called day 0 or day 28 (position 1). In this position, the illuminated surface is not visible from earth, so the moon cannot be seen from earth.
Four days later, when the moon is in position 2, a small part of its illuminated surface is not visible from earth. On day-7, the moon is in position 3, so more of its illuminated part is visible from earth.
After fourteen days (at position 5) the entire illuminated surface of the moon is visible from earth. This is the day of the full moon.
Subsequently, the moon appears smaller with each day as it passes through positions 6 (day-18), 7(day-21) and 8(day- 25). After 28 days, the moon is once again in position 1.
Try to duplicate position 1 with the ball. For this, you will have to hold the ball towards the sun (between your eyesight and the sun).

d) In this position, which half of the ball is illuminated?
Answer: Although half the surface of the moon is illuminated everyday, we cannot see the moon on new moon day since the illuminated surface is on the side opposite to the point of observation on the earth. On a full moon day, the situation is reversed. The illuminated half of the moon faces the point of observation, so we see a full moon.

e) Where is the position of sun and moon on new moon day and full moon day?
Answer:
The sun and moon must be on the same side of the earth on a new moon day and they are on opposite sides of the earth on a full moon day.

f) Can you now state as to in which direction the moon will rise on a full moon day?
Answer:
The moon will rise from west on full moon day.
While we observe moon in clear sky on a full moon day, we think about the spots those are visible on the moon. In olden days people are curious about the spots. This led to creation of a lot of stories.

e) Do you know any such story?
Answer:
One popular story to account for the dark spot on the moon is that Ganesha, once filled with food, fell from his mouse and broke his stomache. Chandra laughed at this, at which Ganesha injured him by breaking off and throughing one of his tusks and cursed him.

Activity – 7

Question 7.
Observing the movement of constellations (stars).
Take a 20cm x 20cm square sheet of paper and make a 1cm diameter hole in its center. Mark a cross ( X ) on one side of the sheet of paper as shown in figure.

Hold the sheet in front of your eyes with the ‘X’ mark at the bottom and look for the pole star through the hole. Once you have located the pole star, check in which direction the Great Bear and Cassiopeia lie.
Write ‘G’ for Great Bear and ‘C’ for Cassiopeia on the paper in the directions in which you see each of the constellations. Mark the timing at which you made your observation in both cases.
Choose a nearby tree or house as a reference point. Draw a picture of your reference point on the paper sheet taken, clearly indicating its location. Repeat your observations at one hour intervals. Ensure that you are standing on the same spot each time you look at the stars.
Write G, C in the direction of the position of the great bear and Cassiopeia during each observation and note the time of the observation next to the letters G and C.
Using the tree or house you have chosen as your reference point, check whether the position of the pole star has changed or not. If it has changed, note the changed position.
Repeat this activity as many times as possible, the minimum being four times. But ensure that the ‘X! mark on your sheet of paper remains at the bottom during all your observations.

a) Do the positions of the stars change with time?
Answer:
Yes, they will change.

b) Does the position of the pole star also change with time?
Answer:
No, it will not change with time.

c) Does the shape of the great bear and Cassiopeia change with time or does the position of the entire constellations in the sky change?
Answer:
The position of entire constellation changes.

d) What kind of path do these constellations trace in the sky?
Answer:
They traced in northern sky.

Activity – 8

Question 8.
Why does the pole star appears fixed at one point?
Take an umbrella and open it. Make about 10-15 stars out of white paper. Paste one star at the position of the central rod of the umbrella and others at different places on the cloth near the end of each spoke.

Now rotate the umbrella by holding its central rod in your hand. Observe the stars on the umbrella.
a) Is there any star which does not appear moving? Where is this star located? Is it located where the rod of the umbrella holds the cloth of the umbrella?
Answer:
Yes, it is located where the rod of the umbrella holds the cloth of the umbrella.

b) On similar lines, if there were a star located where the axis of rotation of the earth meets the sky, could this star is also be stationary?
Answer:
Yes, that is the reason pole star does not move even though all stars appear that they are moving because of rotation of earth.

AP State Syllabus AP Board 8th Class Biology Important Questions Chapter 3 Story of Microorganisms 2

AP State Syllabus 8th Class Biology Important Questions 3rd Lesson Story of Microorganisms 2

8th Class Biology 3rd Lesson Story of Microorganisms 2 1 Mark Important Questions and Answers

Question 1.
What are antibodies?
Answer:
Whenever a disease causing microorganisms enter in our body, it produces some de¬fenders to fight against them, these are called antibodies.

Question 2.
Which one is better to take antibiotics or vaccines?
Answer:
Vaccines are better than antibiotics when the disease is prevented by vaccine.
Ex: Tuberculosis, Tetanus, etc.

Question 3.
What questions do you ask on role of mosquitoes and houseflies in spreading the diseases like Malaria and Swine flu?
Answer:

1. How can we be safe, without affected by malaria and typhoid?
2. Which organisms spread diseases like malaria and typhoid?

Question 4.
What is ‘Triple Antigen Vaccine’?
Answer:
D.P.T vaccine which prevents

1. Diptheria
2. Pertusis (Wooping cough)
3. Tetanus

Question 5.
What is Tet – vac?
Answer:
Tet – vac is the vaccine that is used to prevent Tetanus.

Question 6.
What is M.M.R vaccine?
Answer:
M.M.R is the vaccine that prevents the

1. Measles
2. Mumps
3. Rubella

Question 7.
Name the vaccine that prevents T.B.
Answer:
B.C.G (Bacillus Cardio Gram)

Question 8.
What is the mode of transmission of Dengue disease?
Answer:
Aedes Mosquitoes spread Dengue disease.

8th Class Biology 3rd Lesson Story of Microorganisms 2 2 Marks Important Questions and Answers

Question 1.
Mention different questions to know about antibiotics.
Answer:

1. What are antibiotics?
2. In which year penicillin was announced as antibiotic?
3. Can antibiotics destroy the viruses?
4. Write different types of antibiotics.

Question 2.
Prepare different questions to know the importance of vaccines.
Answer:

1. Name the scientist who invented vaccines first.
2. What type of materials used for preparation of vaccines?
3. Name the vaccine which is used to prevent rabies.
4. Name the disease which is eradicated by vaccine.

Question 3.
Ask different questions about the significance of microbes.
Answer:

1. Name different nitrogen fixing microbes.
2. Can all microbes useful to mankind?
3. What will happen if vaccines are not invented?
4. Write about significance of microbes.

Question 4.
Make a sketch of Nostoc.
Answer:

Question 5.
How is preservation of food helps us?
Answer:

1. Preservation prevents spoilage of food.
2. It helps us to store food for a longer time without spoilage.
3. Variety of food items may be available in off seasons also.

8th Class Biology 3rd Lesson Story of Microorganisms 2 4 Marks Important Questions and Answers

Question 1.
Which one is better to take antibiotics or vaccines? Why?
Answer:
Antibiotics are small molecules or compounds that are effective in treating infections caused by organisms such as bacteria, fungi and protozoa. Some antibiotics act by killing the bacteria while others prevent the bacteria from multiplying, leaving your own immune system to ‘mop them up’.
Vaccines are dead or inactivated organisms or compounds that are used to provide immunity to a particular infection or disease.
Vaccines are used to prevent infection, particularly viral infections. Vaccines are produced from portions of viruses or viruses that are rendered harmless.
The killed or modified virus is introduced into the body where it stimulates part of the body’s natural defenses against infection without causing the illness itself.
Because of this, if the body is exposed to the specific virus in the future, it will recognize it and can fight the infection off much more quickly and effectively, meaning that you don’t succumb to the illness.
Hence vaccines are better than antibiotics when the disease is prevented by vaccine. Ex: Tuberculosis, Tetanus, etc.

Question 2.
Refrigerator helps us in saving health and money. Can you explain?
Answer:
Food and drink, being organic in origin, does not last forever. Shortly after food is bought or prepared it will begin to spoil, quickly becoming inedible through the effects of bacteria. By lowering the temperature of the food through refrigeration, you can slow or even temporarily halt the effects of bacteria, making the food stay edible longer.we can also transport fruits vegetables and other food items up to long distances by using refrigerators. Refrigerator is more useful to keep vaccines and medicines for long time. Hence we can save money and as well as health.

Question 3.
Take root nodules of any pulse or leguminous plants crush on a slide, and draw a rough sketches of what you observe under microscope.
Answer:

Question 4.
Can you give some important key points you noticed that scientists followed in their inventions and discoveries?
Answer:
Invention of microscope is most important one to find out microorganisms. Basing on this several inventions were made, which break the unsolved problems since 400 years. This credit goes to Antonie van Leeuwenhoek who invented single lens powerful microscope, which could magnify the object 300 times. His curiosity and skill of making powerful lenses were the secrets of this invention of powerful microscope.
Dr. Alexander Flemming observed some fungi were preventing the growth of bacteria in his experiments. He separated the substances released by the fungus and tested it on some other disease causing bacteria. This substance also killed many other diseases causing bacteria and named it as Pencillin. The discovery of pencillin paved the way to the discovery of many antibiotics like streptomycin, erythromycin etc.
After several attempts Ross suddenly realized that he used the wrong species of mosquitoes in his experiments. His assistant brought larvae, which hatched to several dappled winged mosquitoes. Delighted with this capture Ross identified Anopheles mosquito is the host for malarial parasite.

Question 5.
Which invention is most important one related to microorganisms? Can you explain the reasons why it is so important?
Answer:
Invention of microscope is most important one to find out microorganisms. Basing on this several inventions were made, which break the unsolved problems since 400 years. This credit goes to Antonie van Leeuwenhoek who invented single lens powerful microscope, which could magnify the object 300 times. His curiosity and skill of making powerful lenses were the secrets of this invention of powerful microscope. Later several microbes were identified by using microscopes. This provides a good source to recognize several diseases and treatment by vaccines and antibiotics.

Question 6.
What are antibodies? When do they develop? How they help us?
Answer:
Whenever a disease causing microorganisms enter in our body, it produces some defenders to fight against them, these are called antibodies. The lymphocytes of white blood cells develop antibodies against to the antigen of pathogen. Antibodies fight the disease causing microorganisms and make resistant to particular strains. Antibodies are used by the immune system to identify and neutralize foreign objects such as viruses and bacteria.

Question 7.
If there are no microorganisms on the earth what will happen?
Answer:
Microorganisms are present everywhere, they are to be found in air, water, soil within the bodies of animals and plants. Some microorganisms are very useful and help us in many ways while some of them are harmful. Microorganisms are most essential to maintain inorganic and organic cycles, to give freshness to the nature by degrading waste organic matter and as well as to fight against harmful microorganisms. Hence no life will be sustained in the nature if there are no microorganisms on the earth.

Question 8.
Prepare a table showing some of plant diseases, causative microorganisms and mode of transmission.
Answer:

Question 9.
If there are no microorganisms on the earth what will happen?
Answer:

1. If micro organisms are not present on earth the earth will be full of dead organisms and plants.
2. The plants can not fix the atmospheric nitrogen in the soil.
3. We can not get fermented products.
4. The life becomes impossible on the earth.

8th Class Biology 3rd Lesson Story of Microorganisms 2 Important Questions and Answers

Question 1.
Many people to. a colony are suffering from ‘Cholera’. What do you think could be the reason?
Answer:

1. The main reasons for the spread of cholera is consumption of contaminated food and water. House flies rapidly spread this disease among people.
2. I would imagine that people were not following personal hygienic practices before consuming food and water.
3. Perhaps people might not be keeping their surroundings clean and hygienic.
4. Perhaps the people might have poor sanitary conditions.

Question 2.
Suggest any two methods of fish preservation.
Answer:

1. Drying
2. Smoking
3. Canning
4. Chilling

Question 3.
What is symbiosis? Give two examples for it.
Answer:

1. In Greek language, symbiosis means “living together”.
2. Symbiosis is any type of a close and long term biological interaction between two different biological organisms in which both are benefited.
3. Examples for symbiotic relationship is Rhizobium. Rhizobium bacteria is living in the root nodules of legume plants.
4. Rhizobium fixes the atmospheric nitrogen in the form of nitrates which are very essential for the growth of plants. Inturn legume plants provide shelter for Rhizobium. Here, both are benefited.
5. Another example for symbiosis is Lichens. Here, we can see the symbiotic relationship between Algae and Fungi.

Question 4.
In an experiment if we keep the dosa dough in Bacillus free chamber, what changes can you observe in the dosa dough after one day?
Answer:

1. Fermentation of dosa dough will not take place.
2. The volume of the dosa dough will not increase and it will not turn into spongy texture.

Question 5.
Classify the given below microorganisms into useful and harmful microorganisms.
Plasmodium, Lactobacillus, Rhizobium, Pencillium, Yeast, Virus.
Answer:
Useful microorganisms:

1. Lacto bacillus
2. Rhizobium
3. Pencillium
4. Yeast

Harmful microorganisms:

1. Plasmodium
2. Virus.

Question 6.
What will happen if we add butter milk to chilled milk?
Answer:
If we add a few drops of butter milk to chilled milk 1) the milk will not turn into curd. It is because, cold milk won’t provide the conditions to grow lactobacillus. Hence, curd will not be formed.

Question 7.
If you are going to conduct a quiz on micro-organisms, what type of questions do you prepare for the quiz programme?
Answer:

1. Can you name the scientist who discovered the pencillin?
2. Name the bacteria that converts the milk into curd.
3. Can you name the food items that can be preserved through pasteurisation?
4. Can you name the microorganism which is very helpful in the preparation of alcohol?

Question 8.
What is the name of the nitrogen fixation bacteria in the root nodules?
Answer:
Rhizobium

Question 9.
What precautions do you take to avoid diseases?
Answer:

1. We should consume boiled, purified water and healthy food daily.
2. Keep our surroundings neat and clean.
3. We should take vaccines to prevent different diseases.
4. We should practice personal hygiene and good sanitary habits.

Question 10.
Defecation in open areas spreads micro-organisms easily. Write some slogans to conduct a rally to protect us from micro-organisms.
Answer:

1. Keep your country clean by keeping your area clean.
2. Stop being so open….. else everything is broken.
3. Use a toilet. Don’t let anything spoil it,
4. Use a toilet – to achieve Swach Bharath.

Question 11.
Draw a table of microorganisms and its diseases.
Microorganisms : Virus, Bacteria, Protozoa, Arthropods.
Disease: Scabies, Malaria, Polio, Typhoid.
Answer:

Question 12.
Why is the idly or dosa batter prepared one day before?
Answer:
If we prepare idly or dosa batter one day before, fermentation occurs in it, carbondioxide gas fill the batter increasing it’s volume and makes it spongy.

Question 13.
Read the following passage and answer the following questions.
When an infected person sneezes or coughs, the pathogens enter the air. When this air containing pathogens enters into the body of a healthy person, it may cause cold. These type of diseases which spread from infected people to healthy ones are known as “communicable diseases”. These get spread through air, water, food or through physical contact of infected person or through insects like houseflies and mosquitoes. Common cold, conjunctivitis, typhoid, smallpox, chickenpox, swine flu, tuberculosis are some examples of communicable diseases. Some insects and animals carry diseases causing microorganisms. They are called as ‘vectors’. The microorganism ‘plasmodium’causes malaria. The female Anopheles mosquito carries plasmodium and thus is a vector. Mosquitoes are vectors for other diseases as well. By controlling mosquitoes, we can prevent dis¬eases caused by them. Mosquitoes breed in stagnant water. We should be careful not to let water collect anywhere in our surroundings, including left over waste pots, waste flower pots, tyres, bowls etc.
a) What are communicable diseases? Give examples.
b) What are vectors?
c) Name the vector which spreads malaria.
d) How do you prevent spread of malaria?
Answer:
a) The diseases which spread from infected people to healthy ones are known as “communicable diseases”.
Eg: Conjuctivitis, Common cold, Smallpox, Rubella, Typhoid, etc…
b) The insects and animals which carry disease causing microorganisms are called as “vectors”.
c) Female Anopheles mosquito.
d) By controlling mosquito population.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 10 Reflection of Light at Plane Surfaces Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 10th Lesson Reflection of Light at Plane Surfaces

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces Textbook Questions and Answers

Improve Your Learning

Question 1.
State the laws of reflection of light (OR)
Name the laws of reflection of light
Answer:
Laws of reflection:

1. When light gets reflected from a surface, the angle of reflection is equal to the angle of incidence, i.e., ∠i = ∠r.
   
2. The incident ray, the normal at the point of incidence and the reflected ray lie in the same plane, i.e., AO, ON, OB are in same plane.

Question 2.
How do you verify the 1st law of reflection of light with an experiment?
(OR)
Raghu found that for a plane mirror angle of incidence is equal to the angle of reflection. Write the experiment to prove this fact. (OR)
Prove: ∠i = ∠r (LAB ACTIVITY – 1)
Answer:
Aim: Verification of first law of reflection.
Required materials: Mirror strip, drawing board, white paper, pins, clamps, scale and pencil.
Procedure:

1. Take a drawing board and fix a white paper on it with the help of clamps.
2. Draw a straight line AB at the centre of the paper and also a normal (ON) to AB at the point ‘O’.
3. Draw a straight line PQ making certain angle (angle i) with ON.
4. Fix two pins at P and Q on the paper vertically.
   
5. Observe the images of pins – P’ of the pin P and Q’ of the pin Q, in the mirror kept along the line segment AB.
6. Fix two more pins R and S such that they are in the same line as that of P’ and Q’.
7. Join R, S and 0 as shown in figure.
8. Measure the angle between RS and ON (angle of reflection).
9. We will find that ∠i = ∠r. (angle of incidence = angle of reflection)
10. Repeat the experiment with different angles of incidence and measure the corresponding angles of reflection.
11. We can find angle of incidence = angle of reflection in all these cases.
    Thus first law of reflection is proved.

Question 3.
How do you verify the 2nd law of reflection of light with an experiment?
(OR)
John found that incident ray, reflected ray and normal drawn to surface lie on the
same plane. What are the apparatus required for this experiment? How are you able to prove this fact experimentally?
Answer:
2nd Law of reflection: The incident ray, the reflected ray and normal all lie in the same plane.

1. As shown in the figure, a light ray incident on a plane mirror and touches at a point ‘O’. Here AO is called incident ray.
2. When a ray of light falls on a mirror, the mirror sends it back in another direction OB. Here OB is called reflected ray.
3. Normal is a line which is perpendicular to the mirror at the point of incidence. So the line ON’ is the normal to the mirror surface at point ‘O’.
   
4. Here the incident ray (AO), the reflected ray (OB) and the normal (ON) all lie in the same plane of the paper.
   Hence 2nd law of reflection is proved.

Question 4.
Explain the image formation by pin hole camera with the help of the diagram.
(ACTIVITY – 1)
Answer:

1. Draw a ray diagram of the formation of an image in a pinhole camera.
2. Observe the flame of a candle with a pinhole camera making a big hole to it.
   
3. We can understand that the light rays coming from the top of the candle flame fall at different points on the screen.
4. Similarly, the rays coming from bottom of the candle points on the screen.
5. Thus, we get blurred image on the screen due to the big hole of the camera.

Question 5.
Find the plane of the reflection experimentally for the incident ray which passes through the heads of the pins pierced in front of the mirror.
(OR)
Sudheer wants to verify the laws of reflection. What apparatus he requires to prove them? State the laws of reflection and write the experimentation process he follows.
Answer:
Aim: Verification of laws of reflection.
Required material: Mirror strip, drawing board, white paper, pins, clamps, scale and pencil.
Procedure:

1. Take a drawing board and fix a white paper on it with the help of clamps.
2. Draw a straight line AB at the centre of the paper and also a normal (ON) to AB at the point ‘O’.
3. Draw a straight line PQ making certain angle (∠i) with ON.
4. Fix two pins at P and Q on the paper vertically.
   
5. Observe the image P’ of the pin P and Q’ of the pin Q, in the mirror kept along line segment AB.
6. Fix two more pins R and S such that they are in the same line as that of P’ and Q’.
7. Join R, S and O.
8. Measure the angle between RS and ON (∠r) .We will find ∠i = ∠r.
9. Repeat the experiment with different angles of incidence and measure the corresponding angles of reflection.
10. We find that each case angle of incidence is equal to angle of reflection. That is first law.
11. We can find that the incident ray is the ray which is passing through points P and Q touching the paper.
12. The reflected ray is the ray which is passing through the points R and S touching the same paper and ON is the normal to the mirror at O. All lie in same plane. That is second law which states incident ray, reflected ray and normal drawn to plane lie in the same plane.

Question 6.
Have you ever observed the image of the sky in rain water pools on earth? Explain the reflection of light in this context.
Answer:
Surface of the rain water pool acts as a plane mirror, because of its smooth surface. The light rays from the sky and clouds incident at this surface and reflect. Hence, the images of the sky and clouds appear in the rain water pools.

Question 7.
Discuss the merits and demerits of using mirrors in building elevation.
(OR)
What are the advantages and disadvantages of using mirrors in building elevation?
Answer:
Merits:

1. The mirrors used in elevating building are tough, reinforced and laminated glasses so they provide safety to the building.
2. They make the building attractive.
3. They absorb heat energy, so they cool inside the building.
4. If we use plane mirrors in building elevation it is easy to wash with water and no need of regular painting.

Demerits:

1. Elevation of buildings with mirrors is not suggestable.
2. These mirrors reflect sun rays at day time and reflects lighting from near by electrical bulbs at night time, which causes confusion and disturbance for the vehicles and people who are running on the nearby roads lead to accidents.
3. Birds like sparrows, crows will get confusion while flying on roads.
4. They are also not safe enough to the buildings, which causes easy access to thieves.
5. This glass elevation is not environmental friendly, because natural air does not enter into the building.
6. They are easy to break and cause cuts and wounds.

Question 8.
If a ray incidence normally on a plane mirror, what will be the angle of reflection.
Answer:
If a ray incidence normally on a plane mirror, the angle of reflection will be zero.

Question 9.
Why does the image in plane mirror suffers lateral inversion?
Answer:
The light rays which come from our right side get reflected from the plane mirror reach our eye. Our brain feels that the rays is coming from the inside of the mirror. That is why our right side looks like left side in the image. This is called right-left inversion or lateral inversion.

Question 10.
Draw a ray diagram to understand the formation of image for a pointed object by a plane mirror explain it.
Answer:
Observe the figure. ‘O’ is a point object.

Some rays from ‘O’ reach the mirror and get reflected. When we look into the mirror, the reflected rays seem to be coming from the point T. So, point I is the image of point object ‘O’.

Question 11.
In the adjacent figure, AO and OB are incident and reflected rays respectively angle ∠AOB = 90°. Find the values of angle of incidence and angle of reflection.

Answer:
We know that angle of incidence is equal to angle of reflection.
i = r …….. (1)
From the figure, ∠AOB indicates i + r = 90°
From (1)
⇒ i + i = 90°
2i = 90°
⇒ i = 90/2 = 45°
⇒ i = r = 45°
Angle of incidence i = 45°; Angle of reflection r = 45°.

Question 12.
Hinduja stands in front of a plane mirror at a distance of 5 m. from the mirror and observes her image in the mirror. If she moves 2 m. towards the plane mirror, then what will be the distance between Hinduja and his image?
Answer:
The distance between plane mirror and Hinduja = 5 m
The distance between plane mirror and Hinduja after moving 2 m towards mirror
= 5 – 2 = 3 m …….. (1)
The distance between plane mirror and Hinduja’s image after moving = 3 m …….. (2)
The distance between Hinduja and her image after moving = (1) + (2) = 3m + 3m = 6m.

Question 13.
Explain diagramatically the Image of letter ‘B’ in a plane mirror.
Answer:

Question 14.
Why can’t we see our image in a white sheet of paper though it reflects light?
Answer:
By microscopic observation, we can find up and downs over surface of a paper. Hence paper is not a smooth fine surface. Even though sheet of white paper reflects the light rays, they do not form an image of an object.

Question 15.
Observe the below figure. AB and BC are two plane mirrors arranged at 120°. A ray incidents at and angle 55° on AB. Find the value of ‘x’

Answer:
Let us say, angles a, b, c, d as shown in the figure. From the figure, a = 55° [∵ i = r]
a + b = 90° [. Normal to the plane]
55° + b = 90°
⇒ b = 90° – 55° = 35°
120° + b + c = 180° [∵ Total of angles in a triangle]
120° + 35° + c = 180°

⇒ c = 180° – 155° = 25° c + d = 90° [∵ Normal to the plane]
25° + d = 90°
⇒ d = 90° – 25° = 65°
d = x [∵ i = r]
∴ x = 65°

Question 16.
The size of the image in the mirror seem to be decreased when you move the object towards your eye from the mirror. Draw the diagram showing angles depicting the situation.
Answer:

Question 17.
Collect the information about “Situations using the plane mirrors and prepare the report.
Answer:
Plane mirrors have many uses.

1. Periscopes: They are used in periscopes to see bends and corners. It is used for observing enemy movements from trenches without any danger of being seen. Sailors on submarines use periscopes to see things above the water level.
2. Kaleidoscopes: Kaleidoscope is a toy that uses light and mirrors to reflect objects and create beautiful, fascinating repeating patterns.
3. Security: Mirrors are used while looking for explosives underneath a vehicle. Even these mirrors are used in shops to keep an eye on the customers. Mirrors are also used in blind turns of busy roads to see the vehicles coming from the other side.
4. Telescopes and Microscopes: Plane mirrors are used in many scientific applications like telescopes and microscopes.
5. Dressing mirrors: Plane mirrors are used in dressing tables to see ourselves, while dressing, shaving, etc.
6. Ophthalmic doctors: They use plane mirrors to increase the distance of the eye test chart while examine the eye of a patient.
7. Docorating mirrors: Plane mirrors are used to decorate the building for elivations. Some shops also used plane mirrors to get multiple images of the items in their shops.

MULTIPLE CHOICE QUESTIONS
1. Angle of incidence = Angle of reflection. This rule is explained by …………… principle        ( )
A) Fermat
B) Newton
C) Archemedes
D) Pascal
Answer: A

2. Which of the following letters doesn’t suffer lateral inversion?         ( )
A) C
B) O
C) B
D) N
Answer: B

3. A ray of light incidents on a plane mirror at an angle of 90° to its surface. What will be the angle of relfection?   ( )
A) 0°
B) 90°
C) 450°
D) 180°
Answer: A

4. If we move an object away from the plane mirror the size of images seems to be     ( )
A) increases
B) decreases
C) of the same size
D) image can’t be seen
Answer: B

5. Which of the following is incorrect with respect to the image in a plane mirror?     ( )
A) Image is erect
B) size of the image is same as the size of object
C) laterally inverted
D) image is real.
Answer: D

6. An object is placed 7cm distance from the plane mirror then distance of image is      ( )
A) 3.5 cm
B) 14 cm
C) 7 cm
D) 21 cm
Answer: C

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces InText Questions and Answers

8th Class Physical Science Textbook Page No. 134

Question 1.
How can we get the image of a big building in a small mirror?
Answer:
Light rays travel in all directions from one object. Light rays coming from a building incident on the small area of a plane mirror and reflect. These reflected rays reach our eye. We see the image of the building in the mirror.

Question 2.
Can we get the image formed by a plane mirror on a screen?
Answer:
Cannot.

Question 3.
Why is there lateral inversion, when we look into a mirror?
Answer:
Our brain feels that the rays is coming from the inside of the mirror.

Question 4.
Why is the angle of reflection equal to the angle of incidence when a light ray gets reflected from a surface?
Answer:
Light always choose the path of least time to travel.

8th Class Physical Science Textbook Page No. 138

Question 5.
Is the angle of reflection equal to the angle of incidence in all cases?
Answer:
Yes.

Question 6.
Do the two rays and the normal lie in the same plane? If yes, which is that plane?
Answer:
Yes, plane of paper.

Question 7.
In which plane will the incident ray, reflected ray and the normal lie?
Answer:
Plane touching the heads of pins and parallel to the plane of paper.

Question 8.
How will the incident ray be?
Answer:
Incident ray touching heads of the pins (P and Q) and make some angle with plane of the paper.

Question 9.
How will the reflected ray be?
Answer:
Reflected ray will make some angle with plane of the paper.

Question 10.
How will the normal be?
Answer:
The normal will also make same angle as incident and reflected rays.

Question 11.
How will the plane of reflection be?
Answer:
Plane of reflection make some angle (which is equal to plane of the paper and incident ray) with plane of the paper.

Question 12.
How does a mirror form the image of a pin or any object? Let us discuss.
Answer:
The rays coming from the pin get reflected from the mirror and seem to be coming from the image in the mirror.

8th Class Physical Science Textbook Page No. 139

Question 13.
What is the size of the image compared to the size of the object?
Answer:
Size of the image is equal to size of the object.

Question 14.
What do you say about the size of the image compared to the size of the object? Move the object towards your eye. What do you observe?
Answer:
Size of the image is same as size of the object. If we move the object towards our eye, size of the image of the object seems to be decreased.

Question 15.
Is the size of the image decreasing or increasing?
Answer:
Decreasing.

8th Class Physical Science Textbook Page No. 140

Question 16.
Why does an image suffer lateral (right-left) inversion? See the figure.

Answer:
Our brain feels that the rays are coming from the inside of the mirror and image is opposite to us. In this way image suffer lateral inversion.

Question 17.
What do you understand from the figure?
Answer:
The light rays which come from our right ear get reflected from the plane mirror and reach our eye. Our brain feels that the ray is coming from the inside of the mirror. That is why our right ear looks like left ear in the image.

Think, Discuss and Write

8th Class Physical Science Textbook Page No. 135

Question 1.
Does the explanation on pinhole match with your observation?
Answer:
Yes, it matches with my observation.

Question 2.
What happens if the hole Is much bigger, i.e., equal to the size of the flame?
Answer:
The image is extremely blurred.

Question 3.
If so, can we get the image of flame on the screen of pinhole camera? Why?
Answer:
No. Because the light rays coming from the top of the flame and bottom of the flame fall at different points on the screen. So it is blurred and is not formed on screen.

Question 4.
What happens if we observe the same flame with the same pinhole camera from a long distance?
Answer:
We may observe not only the flame, but the blurred image of entire candle.

Question 5.
What happens if we made two holes to pin hole camera?
Answer:
Two images will be formed.

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces Activities

Activity – 2

Question 1.
Which grain on the ground that a smart crow on tree A pick to reach B in short time (Shortest path)? Explain. (OR)
How do you support your answer to “When light gets reflected from a surface, it selects the path that takes the least time”? (OR)
Explain Fermat’s principle by using an activity.
Answer:

1. The crow can pick the grain from any point on the ground, but the condition is selecting the shortest path.
2. Let the speed of the crow is constants –
3. Observe some of the paths in figure.
4. To compare the lengths of these paths ACB, ADB, AEB and AFB, make the duplicates of them at point G as shown in figure.
5. In the figure CB = CG,
   ∴ The length of path ACB = AC + CB = AC + CG = ACG
6. Similarly length of the path ADB = length of the path ADG Similarlylength of the path AEB = length of the path AEG Similarly length of the path AFB = length of the path AFG
7. By observing the above paths, we will notice that AEG is the shortest path among all the paths, because it is the straight line distance between points A and G.
8. So the smart crow will pick the grain from point E.

Activity – 3

Question 2.
Look at the following figure.
Suppose if you have been given a plane mirror strip, what will you do to obtain figures as shown below figure (b) using mirror strip and the above figure (a)?

Answer:
The place of mirror that should be place on the figure vertically has been shown here under by a line.

In the above diagrams, line indicates the position of mirror to be kept to get the required shapes.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 9 Electrical Conductivity of Liquids Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 9th Lesson Electrical Conductivity of Liquids

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids Textbook Questions and Answers

Improve Your Learning

Question 1.
Give examples for good solid conductors and liquid conductors.
Answer:
Examples for good conductors in solids:
Silver, copper, iron, graphite, etc.
Examples for good conductors in liquids:
Mercury, acid solutions (HCl, H₂SO₄), base solutions (NaOH, KOH), salt solutions (NaCl, KCl), etc.

Question 2.
Give examples for bad solid conductors and liquid conductors.
Answer:
Examples for poor conductors in solids:
Gold, platinum, etc.
Examples for bad conductors in liquids:
Distilled water, coconut oil, petrol, vegetable oil, kerosene, alcohol, etc.

Question 3.
What do you add to distilled water for making it to conduct electricity?
Answer:
Distilled water is poor conductor of electricity. In order to increase conductivity we should have to add either acid, base or salt. That will increase the conductivity of distilled water due to decomposition of these substances into constitute ions.

Question 4.
What is an electrolyte ?
Answer:
Electrolyte is a solution of substance through which current can pass.

Question 5.
Which energy is cause for glowing of bulb in electrolytic cell?
Answer:
Electrolytic cell is a device which converts chemical energy into electrical energy. So chemical energy stored in the cell is cause for glowing of bulb.

Question 6.
Write the uses of electroplating.
Answer:
Uses of electroplating:

1. Metals like iron are coated with deposits of nickel or chromium to prevent rusting.
2. Machinery parts are often chromium plated to protect them from corrosion and at the same time to give them good polish.
3. Electroplating is also used in repairing worn out parts of machinery.
4. Electroplating is also done for ornamentation and decoration purposes.
5. Processed food items are preserved in tin coated iron cans by electroplating method.
6. Zinc coated iron by electroplating method is used for bridges and in automobiles.

Question 7.
In case of a fire, before the fire men use the water, they shut off the main electrical supply for the area. Explain why they do this.
Answer:
Fire men use water to put out fire. Water containing dissolved salts is a good conductor of electricity. If fire men pour water on fire the electrical appliances near the fire may be wet if anybody touches those appliances they may have electric shock. In order to avoid people to get electric shock due to wet electrical appliances the fire men shut off electrical supply before they use water.

Question 8.
We get some items made from iron wire in which iron wire is coated with plastic. Is plastic coated by the process of electroplating? Why plastic cannot be coated on a metal by the process of electroplating?
Answer:
No. Plastic cannot be coated on a metal by using electroplating. The reason is plastic being a carbon polymer does not dissociate into ions. So it does not allow passage of current. So it does not act as an electrolyte. So electrolysis process is not possible with plastic which is main criteria for electroplating. So plastic cannot be coated on a metal by the process of electroplating.

Question 9.
Kavya observed that a discharged dry cell which kept in sunlight by her father for few hours got ability to glow LED. She got many doubts and questions to raise. Can you guess those questions or doubts? (OR)
Rohan observed that a discharged dry cell which kept in sunlight by his brother for few hours got ability to glow LED. He got many doubts and questions to raise. Guess the doubts or questions.
Answer:

1. Why does the bulb glow?
2. How does the dry cell charged?
3. Which energy is useful in charging the discharged dry cell?
4. Shall we use that energy to get rid from electrical power cut?

Question 10.
Explain the process of coating copper on iron key. Draw the circuit diagram.
(OR)
Conduct an experiment for coating on iron key with copper by electroplating method and prepare a note.
Lab Activity
Answer:
Aim: Coating an iron key with copper by electroplating method.
Required material: Copper plate of size 2 cm x 5 cm, crystals of copper sulphate, a key made by iron, glass beaker, water, sulphuric acid, battery cell and some connecting copper wires.
Procedure: Dissolve crystals of copper sulphate in pure water to prepare concentrated solution. Pour the solution in a beaker and add a few drops of dilute sulphuric acid to it.

Tie one end of connecting copper wire to iron object to be coated with copper. Connect other end to the negative terminal of battery. Suspend the tied iron object into the copper sulphate solution. Suspend the copper plate into copper sulphate from positive end of the battery through a switch as shown in the above figure. Key and plate are a little away from each other. Put the switch on for about 10 minutes. Switch the circuit off and take the iron key out.
We can observe a red coating on iron key. The reason is when electric current is pass through copper solution, in which copper sulphate is present in the form of copper and sulphate ions. The copper ion gets drawn to the electrode connected to the negative terminal of the battery and deposited on it.

Question 11.
How do you appreciate the efforts of Luigi Galvani and Alessandro Volta in discovering a cell and making a stored electric energy available to human beings?
Answer:
We should have to thoroughly appreciate the efforts of Luigi Galvani and Alessandro for their discoveries for the development of mankind. Galvani and Volta completely change the life of human beings. Before that people generated electricity in different ways and conduct various experiments. However they faced one major problem which prevented them from understanding electricity in depth. They did not have a stable and permanent source of electricity. Galvani experimental conclusion was a revolution in science saying that all living beings contained electricity and it was the main source of life.
Volta proved it is possible to generate electricity if two different metals are placed in some liquids. Volta made first cell using zinc and copper dipped in sulphuric acid. This cell called Volta cell. Later dry cell was prepared. Now various appliances works with dry cells. So the efforts of Galvani and Volta should be appreciated by every generation for their contribution to electricity.

Question 12.
Collect the information and make a list of good conductors and bad conductors. Mow do you use this information in your daily life works?
Answer:

Applications in daily life: This information is very useful to us. Generally metal or good conductors of electricity are used in electrical appliances, electrical wires, fuse wires, etc. Whereas plastic is a bad conductor is used for electric insulators like gloves, handles of electrical appliances etc. to avoid electric shocks.

Question 13.
Make a battery from four lemons and test it with a LED in the circuit.
(OR)
Write how do you make a battery from four lemons and test it with a LED in the circuit in your laboratory.
Answer:
Take four lemons cut them into two pieces. Take one piece from each lemon and insert two copper wires and connect them in series and connect a LED and complete the circuit. The circuit is shown below.

The bulb glows due to presence of current in the circuit. Here lemon juice acts as electrolyte and copper wires acts as electrolyte. So each lemon piece dipped with a copper wire acts as cell. These cells connected in series forms a battery.

Question 14.
Refer to the activity 3 in this chapter. Start with distilled water. The LED would not glow. Add two drops of some acid to distilled water and check the glow of LED. Add two more drops and check the intensity of the glow. Repeat the activity 5 to 6 times by adding 2 drops of the same acid each time. Do you see any difference in the intensity of glow with increasing acid content of water? What can be inferred from the above observations? Repeat the entire activity by taking a solution of baking soda and adding drops of it to distilled water instead of acid. Write differences and similarities.
Answer:
When we add two drops of acid (namely hydrochloric acid) to distilled water the LED will glow. If we further add the acid another two drops the intensity of glow increases. By repeating same activity 5 or 6 times we observe every time the glow of LED increases. The reason is acid dissociate into ions in aqueous solution. Which allows the passage of current. As the quantity of acid increases there will be more ions available for passage of electricity. So the intensity of glow increases.
We will observe the same result by adding baking soda but the intensity of glow is some what less when compared with addition of acid. The reason is baking soda is a weak base. So the dissociation is less when compared with acid. So less ions are available for passage of electricity. So the intensity of glow of LED is less when compared with acid.

Question 15.
In many of the activities in this chapter, we have used a tester made up of LED. Can we avoid LED and use something else as a tester Magnetic compass needle could be an alternative tester. We know that when we take a current carrying wire near magnetic compass needle, it shows deflection. Use this property to make a tester of magnetic compass needle. You may refer to the following figure.
Answer:
A magnetic compass wound with a copper wire is connected to one end of dry cell. The other end is connected to one of the two metal pins separated by a small gap in a rubber cap. The second pen is connected to the other end of dry cell to completed the circuit.

The magnetic needle deflects because whenever current pass through a wire it acts as a magnet is called magnetic effect of current.

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 123

Question 1.
Why some material allows electric current to pass through them and why some do not?
Answer:
Flow of charged particles constitutes current. So for the passage of current the material should have charged particles. All the materials do not have charged particles, e.g. Plastic, wood, diamond, etc. So only those material which have charged particles allow passage of current.

8th Class Physical Science Textbook Page No. 127

Question 2.
If a battery is packed in a box and if only two wires from two terminals are given out, how can we decide the positive and negative terminal of the battery?
Answer:
Insert the wires into a potato. A greenish spot is seen on potato at one of the wires. That wire behave like positive terminal and the other is negative terminal.

8th Class Physical Science Textbook Page No. 129

Question 3.
What is electrolysis?
Answer:
The dissociation of a solution of compound into constitute ions or elements by passing current is called electrolysis.
e.g. Electrolysis of water, which produce oxygen and hydrogen gases.

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids Activities

Activity – 1

Question 1.
Testing the material to know which allows electric current to pass through it.
Answer:
Take a torch bulb or LED (Light Emitting Diode), a dry cell, wooden sheet, two drawing pins, a key (safety pin) and pieces of connecting wires. Set up the electric circuit as shown in the figure.

Place the key on drawing pin. The bulb begins to glow as soon as the key touches the drawing pin. Now replace the key by a nail.
Does the bulb glow ?
Yes, the bulb glows.
Repeat the activity using different types of materials instead of the nail, say a strip of paper, a piece of chalk, a drinking straw, a piece of plastic, a paper clip, a rubber eraser, etc.
Note in each case whether the bulb glows or not and enter your observations in table.

From the above activity, we conclude that some material allow electric current to pass through them. What we call them?
They are called good conductors of electricity.
The material that do not allow current to pass through them, what is the name given to those material?
They are named as bad or poor conductors of electricity.

Activity – 2

Question 2.
Testing the electric conductivity of liquids.
(OR)
Conduct an experiment for testing the electric conductivity of liquids.
Answer:
Take a LED, dry cell, metal pins, rubber cap of injection bottle and wires for making connections. Set up an electric
circuit shown in the figure.

See that the two metal pins, pass through the cap and should have a very small gap (around 2 mm) between them so that the pins are fairly closer but not touching each other. The LED should not glow when pins are separated by small distance.
Now, join the free ends of pins together by pressing them for a moment and make sure that the LED glows. Release the pins they get separated and LED should not glow. This acts as a tester.
Fill the rubber cap with different liquids like distilled water that we drink, coconut oil, kerosene, lime juice, mustard oil, sugar solution, etc one after another and in each case check whether the LED glows or not. Note down your observations in table.

a) Why doesn’t the LED glow in all the cases? Or why doesn’t the LED remain off in all the cases?
Answer:
The LED doesn’t glow all the cases because when the liquid the two pins of tester allows electric current to pass through, the circuit is completed (closed) and the LED glows. On the other hand when the liquid does not allow the current to pass through, the circuit is incomplete (open) and the LED does not glow.

b) In the above activity, you may have observed that in all those cases where the LED glows, its brightness (intensity) is not the same. Sometimes it may be brighter and sometimes it may be relatively dimmer. Why is that so?
Answer:
The intensity of the glow of the LED depends on the flow of electric current through the circuit. Although a liquid may be a conductor, it may not allow current through it as easily as a metal does.
As a result although the circuit is completed and the LED glows, due to weak current in case of some of the liquids, the intensity of glow would be lower compared to other liquids.

Activity – 3

Question 3.
Transforming a poor electric conductor into a good conductor.
(OR)
Conduct an experiment for testing the electric conductivity of electrolyte.
Answer:
Take some amount of distilled water in three different containers. Dissolve small quantity of common salt in the water of first container. Dissolve the copper sulphate, lemon juice in second and third container respectively.
Use the tester that we used in activity 2, and repeat the activity 2. Note the observations in table.

a) From table what can we infer?
Answer:
Distilled water does not allow the electric current to pass. Water in its pure form is a bad conductor of electricity. But when water contains salts or acids, it allows a passage of electric current and turns into a good conductor of electricity.

b) Do you understand why you are advised not to touch electric appliances with wet hands?
Answer:
Water with salts is a good conductor of electricity and the current flowing through househt d electric appliances is very high. Therefore we should never touch the electrical appliances with wet hands.

Activity – 4

Question 4.
Testing the effect of electric current on potato.
Take a potato. Cut into two halves and take one half of it. Construct tester with LED bulb. Insert two copper wires of the tester into the potato. Leaving some distance (around 1 cm) between them.

a) Dose the LED glow?
Answer:
Yes, the LED glows.
Leave the inserted wires for 20-30 minutes.

b) What do you observe the surface of the potato?
Answer:
A greenish blue spot is seen on the potato around the wire connected to the positive terminal of the battery.
But no such spot is seen around the other wire connected to the negative terminal. This greenish spot is due to chemical change in the potato.

c) What could be the cause behind this change?
Answer:
There is chemical change occurred in the potato.

d) Will other vegetables also show such an effect?
Answer:
Vegetable like carrot, beetroot, cucumber, radish, sweet potato show the chemical change there by the LED glows.

Activity – 5

Question 5.
Make your own cell.
(OR)
Draw the diagram of electrolytic cell and explain.
Collect two injection bottles. Cut two 5 cm long bits of thick copper wire. Use sandpaper to scrap about 1 cm of the coating off both ends of the wires.
Break open a exhausted dry cell and remove its outer metal covering (made of zinc). Cut two 2 mm wide and 5 cm long strips from this zinc plate. Insert the copper wires and zinc strips into the rubber caps of the injection bottles as shown in figure. Ensure that the copper wire and zinc strips do not touch each other.

Now take a wire and connect the copper wire of one bottle with the zinc plate of the other bottle. Fill both bottles with dilute sulphuric acid. Carefully close the bottles with the caps in which copper wires and zinc strips are inserted. Your cell is ready.
How will you test it?
Take an LED. Attach two wires to its two terminals. Touch the wire from one terminal to the zinc plate and the wire from other terminal to the copper wire. Did the LED light up ? If not, change the connections vice-versa. Did the LED glow ?
Repeat the above activity using lemon juice, tamarind juice and tomato juice one by one instead of sulphuric acid to make cells.

a) What other liquids can be used to make the cell?
Answer:
Acid solutions.

b) Will detergent solution be useful?
Answer:
Yes, it is useful.

c) How does above cell function?
Answer:
After a few seconds of immersion of zinc and copper into dilute sulphuric acid, zinc slowly begins to dissolve in the sulphuric acid. We can see bubbles getting formed on the copper rod.
The current is passed from copper rod to zinc rod. Here chemical energy is converted into electric energy by electrolysis method.

d) Can you compare this cell with dry cell?
Answer:
In the above cell electrolyte is dilute sulphuric acid whereas in dry cell ammonium chloride paste is electrolyte. The electrodes in above cell is copper and zinc, whereas in dry cell it is graphite (carbon) and zinc.

e) Which is good one? Why?
Answer:
Dry cell is better than ordinary Volta cell. The reason dry cell does not have any fluids. So it is easy to carry dry cell compared with volta cell. So dry cell is better than volta cell.

AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 4 Synthetic Fibres and Plastics

AP State Syllabus 8th Class Physical Science Important Questions 4th Lesson Synthetic Fibres and Plastics

8th Class Physical Science 4th Lesson Synthetic Fibres and Plastics 1 Mark Important Questions and Answers

Question 1.
What is polymer?
Answer:
Many small identical units combine to form a large unit is called polymer. The small units are called monomers.

Question 2.
What are synthetic fibres?
Answer:
The fibres obtained from petrochemicals when they are subjected to chemical processes are called synthetic fibres.
Have you ever heard a cracking sound when you take off certain type of clothes? or did you see sparks in them when it is dark?

Question 3.
What is the reason?
Answer:
This is static electricity developed by artificial fibres due to friction.

Question 4.
Why does wearing nylon clothes are not preferable while cooking or working near a fire?
Answer:
Nylon fibre easily catches fire. So it is not preferable to wear it while cooking, welding, working near a fire.

Question 5.
What is blending and what is the advantage of blending?
Answer:
Any synthetic fibre can be combined with two or more other fibres is called blending.
When two fibres are blended the resultant blended fibre possess the best qualities of both.

Question 6.
What are the uses of plastics?
Answer:
Plastics are used in milk and oil pouches, containers to store pickles and rice, buckets to store water, chairs, water pipes, electrical appliances, television, radio and comput¬ers and mobile phones.

Question 7.
What material is used to make handles of utensils?
Answer:
Bakelite is used for making handles of various utensils due to its poor conductivity of heat and electricity.

Question 8.
How do you appreciate 4R principle?
Answer:
4R principle is useful in developing ecofriendly environment and bright future for next generation of people.

8th Class Physical Science 4th Lesson Synthetic Fibres and Plastics 2 Marks Important Questions and Answers

Question 1.
How is nylon made? What are the advantages of nylon as fibre?
Answer:
Nylon is a polymer made of chemical units called polyamides.
Advantages of nylon as fibre:

1. Nylon fibre is strong, elastic and light weight.
2. Cloth made of nylon are lustrous and easy to wash.
3. Nylon does not absorb water.

Question 2.
Where does we use nylon?
Answer:
Nylon can be used in tooth brush bristles, ropes, fishing nets, tents, sarees, stockings and socks, car seat belts, sleeping bags, curtains, carpets and also used in making parachutes.
Rock climbers use nylon ropes to climb mountains. It is also used in making of swim suits, sheer hosiery, sails, umbrella cloth, dress materials, car tyres, etc.

Question 3.
How would you prepare rayon?
Answer:
The cellulose that was collected from wood or bamboo pulp is treated with sodium hydroxide and then carbon disulphide. It forms a syrup called viscose. Viscose is forced through a spinneret into a solution of dilute sulphuric acid. This gives us silk like threads. This new fibre is called rayon which is an artificial silk.

Question 4.
What are the uses of rayon?
Answer:

1. Rayon is cheaper than silk and can be woven like silk fibre.
2. Rayon is mixed with cotton to make bed sheets.
3. Rayon is mixed with wool in making of carpets.
4. Rayon is often used in fashion and home furnishings.
5. Rayon is also found in sanitary products, diapers and bandages and lints for dressing wounds.

Question 5.
What is acrylic ? Where do we use acrylic?
Answer:
Acrylic is a synthetic fibre made from the combination of coal, air, water and lime¬stone. It looks like natural wool. If can be considered as artificial wool.
It is used in knitted apparels such as fleece, socks, sportswear and sweaters. It is also used in craft yarns, upholstery fabric, carpets, luggage yawning and vehicle covers.

Question 6.
What are the advantages of natural fibre over artificial fibres?
Answer:
When natural fibres, contribute to a fabric it allows the skin to breathe easily. Also natural fibres are generally free from irritating chemicals. Whenever fire accidents takes place they does not stick to the body.

Question 7.
How do you prepare polyester? What are the advantages of polyester as fabric?
Answer: Polyester is made by reacting dicarboxylic acid with dihydric alcohol.
Advantages :

1. Polyester can be melted and spun. This property allows the fibre to convert into different sizes and shapes.
2. They are altra thin, microfiber which gives them a smoothen and soft feel.
3. They does not get wrinkled easily.
4. It remains crisp and easily washable.

Question 8.
Give example for popular polyester and what are its advantages?
Answer:
The popular polyester is terylene.

1. It can be drawn into very fire fabric fibres.
2. Terylene is after mixed with cotton to form terricot with wool to give terriwool. Which has best qualities of both blunded fibres.

Question 9.
What are plastics? How many types of plastics are there? Explain them with examples.
Answer:
Organic polymers are called plastics. Plastics are two types :

1. Thermoplastics: The plastics which get deformed easily on heating and can be bent are called thermoplastics, e.g.: Polyethene, PVC.
2. Thermosetting plastics: The plastics which molded once cannot be softened on heating are called thermosetting plastics, e.g.: Bakelite, melamine.

Question 10.
Where do we use bakelite?
Answer:

1. Bakelite is used for making handles of various utensils.
2. It is used for making electrical appliances including switch boards.
3. It is an alternative for pearl and jade.
4. In manufacture of telephone.

Question 11.
Where do we use melamine?
Answer:

1. Melamine is used in making of utensils and other grocery of kitchen.
2. It is used for making of floor and dress material (firemen dress) for their nature of fire resistance.
3. Computer and T.V. cabinets are made by melamine.

Question 12.
Ramu observing his grandmother keeping pickles in plastic bottles. What are the questions raised in his mind by seeing this?
Answer:
The questions raised in Ramu’s mind

1. Whether plastic is cheap when compare with metal?
2. Why does she not put the pickles in metal containers?
3. Whether metal containers react with pickles? If so they form harmful substances?

Question 13.
What do you know about creator of first man made plastic? How he prepare the plastic?
Answer:
The creator of first man made plastic is Alexander Parkes the name of the plastic is parkesine.
To prepare this material Parkes heated nitrated cotton which previously soaked in sulphuric acid and made fabric soft and elastic with oil and camphor. The end product was an ivory – coloured material that became distorted when subjected to heat. This is named as Parkesine.

Question 14.
What do you know about father of plastic industry? What are his major inventions and discoveries?
Answer:
Dr. Baekeland is considered as the father of present plastic industry. He was respon¬sible for the invention of bakelite. He accidently discovered the compound of carbolic acid and formaldehyde. When he tried to reheat the solidified compound he discovered it would not melt, no matter how high the temperature would be.

Question 15.
List out the objects made up of Acrylic.
Answer:

1. It is used in knitted apparels such as fleece, socks, sports wear and sweaters.
2. It is also used in craft yarns, upholstery fabric, carpets, lugguage awnings and vehicle covers.

Question 16.
Draw and explain the diagram of Universal recycling symbol.
Answer:
When the number is omitted from recycling icon then it is known as Universal recycling symbol.

Question 17.
What are thermosetting plastics? Give two examples.
Answer:
Thermosetting plastics are synthetic materials which gain strength during moulding by heating, but cannot be remoulded or reheated after their initial heat, moulding.
Ex : Bakelite and melamine.

Question 18.
What made the human beings to search for the alternative for natural fibres?
Answer:
Human being is always going in search of new things which can make his life more comfortable and durable. As the natural fibres are not durable, elastic or light weight or lustrous or easy to wash, he needed an alternative to fulfill his expectations. The solution to his expectations is synthetic fibre.

Question 19.
Imagine what would happen if we do not discover plastics.
Answer:
Nowadays every object used in our day to day life is made of plastic. For example milk and oil pouches, containers to store pickles and rice, buckets to store water, chains, water pipes, electrical appliances, television, radio and computers, mobile phones.
So plastics has taken over the place occupied by metal wood and glass items due to its special properties. So we cannot imagine our life without plastics because it is part of each and every aspect of life.

Question 20.
What is the most common material used in making the household articles ? Give some examples.
Answer:
Mostly household articles are made up of plastics.
Milk and oil pouches, containers to store pickles and rice, buckets to store water, chairs, water pipes, electric appliances, television, radio and computers, mobile phones, etc. are made of plastic.

Question 21.
What are the properties of thermoplastics and thermosetting plastics ?
Answer:
Thermoplastic will soften when heated and harden when cooled. It is a polymer that turns into a liquid when heated and freezes to a very glassy state when cooled sufficiently. Thermosetting plastics are not remouldable or reheatable. They are poor conductors of heat and electricity. They are fire resistants.

Question 22.
Why polyster is quite suitable for making dress materials ? Name any two types of polyesters and their uses.
Answer:
a) Fabric made from polyester does not wrinkled easily.
b) If remains crisp and it is easy to wash.
c) Terylene is a type of popular polyester.
d) It can be drawn into very fine fibres that can be woven like any other yarn.
e) PET is very familiar form of polyester. It is used for making bottles, utensils, films, wires and many other useful products.

Question 23.
Write some disadvantages of synthetic fibres.
Answer:
a) Synthetic fibres cannot absorb moisture, thus they cannot be used as dress materials during summer.
b) They are dangerous to be worn near fire or heat as they catch fire easily.
c) They cannot be easily ironed.

Question 24.
Explain why plastic containers are favoured for storing food.
Answer:
Three main advantages of using plastic containers for storing food are :
a) They do not react with food items
b) They do not get rusted
c) They are light, strong and durable

Question 25.
Explain why the following are made of thermosetting plastics,
a) saucepan handles
b) electric plugs/switches.
Answer:
Above things are made up of bakelite (thermosetting plastic) because it is
a) bad conductor of heat
b) poor conductor of electricity.

8th Class Physical Science 4th Lesson Synthetic Fibres and Plastics 4 Marks Important Questions and Answers

Question 1.
Explain 4R principle for creating ecofriendly environment.
Answer:
The 4R principle involves 1) Reduce 2) Reuse 3) Recycle 4) Recover.

1. Reduce: Reduce the usage of plastic to avoid its negative consequence on environment. Land filling or plastics and burning of plastics in incinerators in the way of disposal of plastics. These have negative consequence on environment. So reduce the usage of plastic whenever it is possible.
2. Reuse: Articles made of plastic is used again and again for its optimum utilization. There by we can decrease the usage of plastics.
3. Recycle: We can recycle the plastic material from broken plastic material that will decrease the production of excess of plastic.
4. Recover: The principle of recover plays major role in plastic waste management. The solid waste should be converted into resources such as electricity, heat, compost and fuel through thermal and biological means.

(OR)

1. Reduce: Try to use less plastic material in our daily life.
2. Reuse: Whenever we need to use plastic material, use the same material again and again don’t go for new one every time.
3. Recycle: Instead of throw away the waste plastic material try to give it the vendor.
4. Recover: Aware the people about establishing “garbage to energy” plant in your area.

Question 2.
Is there any such effort for solid waste management taking place in your village/ town ? How do you appreciate 4R principle?
Answer:
4R Principle is for creating an eco friendly environment.
4R = Reduce, Reuse, Recycle and Recover.
Reduce: Reducing the usage of plastics by reusing them helps the negative conse-quences on environment.
Reuse: When some things made of plastics are not in use to us, we can give them to others who need them. This helps the negative consequence or environment. This is eco friendly.
Recycle: In this process, we can obtain a new substance from the old plastics. Recycling can be used to obtain materials from which the original products were made.
Recover: The solid wastes in which plastics are major should be converted into resources such as electricity, heat, compost and fuel through thermal and biological means.
In these ways 4R principle is eco-friendly.

Question 3.
Explain the differences between the thermoplastics and thermosetting plastics with help of a diagram explaining in terms of arrangements of monomers.
Answer:

Explanation:

1. Thermoplastics have linear arrangement of monomers.
2. But thermosetting plastics have cross linked arrangement.
3. The difference in the arrangement of monomers bring the difference in their properties.

Question 4.
Do you know how various synthetic fibres are obtained ?
Answer:
Nylon:
Nylon is a polymer made of chemical units called polyamides which contain carbon, oxygen and nitrogen. Polyamides are melted and forced through a heated spinneret which has very, very tiny holes. The size and shape of the holes changes, the characteristics of the resulting fibre. The fibre solidifies as it cool and can be spun or woven.

Rayon:
The cellulose that was collected from wood or bamboo pulp, is treated with several chemicals.
First sodium hydroxide is added and then carbon disulphide to the cellulose.
The cellulose dissolves in chemicals add to it and gives a syrup called viscose. Viscose is forced through a spinneret, into a solution of dilute sulphuric acid. This gives us silk like threads. The threads are cleaned with soap and dried. This new fibre is called rayon.

Acrylic:
It is made from the combination of coal, air, water, oil and limestone. It is spun by either dry spinning or wet spinning.
In dry spinning the dissolved polymers are extruded into warm air. The fibres solidify by evaporation. In wet spinning the polymers are dissolved and extruded into a bath and then dried.

Question 5.
Can you name the few things made up of i) nylon ii) rayon (iii) acrylic and (iv) polyesters ?
Answer:
The things made from nylon:
Tooth brush bristles, ropes, fishing nets, tents, sarees, stockings and socks, car seat belts, sleeping bags, curtains, etc. are made up of nylon. The things made from rayon: Bed sheets, carpets, home furnishings, sanitary products, diapers and bandages and lints for dressing wounds.
The things made from acrylic: Socks, sportswear and sweaters, craft yarns, upholstery fabrics, carpets, luggage, awnings and vehicle covers.
The things made from Polyester: PET bottles, utensils, films, wires, etc.

Question 6.
Why it is advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen ?
Answer:

1. The synthetic fibres melt on heating.
2. This is actually a disadvantage with synthetic fibres.
3. If the cloth catches fire it can be very disastrous.
4. The fabric melts and sticks to the body of the person wearing it.
5. It is therefore advised not to wear synthetic clothes while working in a laboratory or working with fire in the kitchen.

Question 7.
Classify the material as biodegradable and non-biodegradable.

1. paper
2. wood
3. metals
4. cotton cloth
5. plastic container
6. woolen sweater
7. peels of vegetable and fruit

Answer:

Question 8.
Write short notes on the following.
a) Plastic and health care industry b) Plastic cookware c) Teflon d) Fire proof plastic.
Answer:
a) Plastic and health care industry : Plastics find extensive use in the health care industry. Some examples of their use in health care are the packing of tablets, threads used for stitching wounds, syringes, doctor’s gloves, a number of medical instruments, etc.
b) Plastic cookware: Plastic cookware is used in microwave ovens for cooking food. The heating process is different in microwave ovens. The heat cooks the food but does not affect the plastic vessel.
c) Teflon: Teflon is a non-stick plastic used as non-stick coating in cookwares. It is also used as tape for sealing purpose.
d) Fire proof plastics: Although synthetic fibres catches fire easily, it is interesting to know that the fire proof material is made from synthetic plastics.

8th Class Physical Science 4th Lesson Synthetic Fibres and Plastics Important Questions and Answers

Question 1.
State government decided to avoid Flexi Banners. Predict the effect of Flexi banners
on environment.
Answer:

1. PVC flexi banners can take several years to decompose in land fills.
2. These flexi banners contain dangerous chemical additives like lead, cadmium which can be toxic to our health as well as animals health.

Question 2.
Write two slogans on solid waste management.
Answer:

1. Convert waste to wealth
   Don’t convert wealth to waste.
2. Recycle waste solid today
   for a better solid future.
3. Reuse, Reduce, Recycle
   The good, The bettel, the best

Question 3.
Draw and explain the diagram of Universal redyeing symbol.
(OR)
Draw “Universal Recycling Symbol”.
Answer:
When the number is omitted from recycling icon then it is known as Universal recycling symbol.

Question 4.
Nylon is a synthetic fibre. Write the advantages and disadvantages of it.
Answer:
Advantages of nylon as fibre:

1. Nylon fibre is strong, elastic and light weight.
2. Cloth made of nylon are lustrous and easy to wash.
3. Nylon does not absorb water.

Disadvantages of nylon as fibre:

1. Synthetic fibres cannot absorb moisture, thus they cannot be used as dress materials during summer.
2. They are dangerous to be worn near fire or heat as they catch fire easily.
3. They cannot be easily ironed.

Question 5.
Though there are so many harmful effects of plastic, we still prefer to use it. What could be its major advantages?
Answer:
Plastics are used in milk and oil pouches, containers to store pickles and rice, buckets to store water, chairs, water pipes, electrical, appliances, television, radio and computers and mobile phones.
Bakelite is used for making handles of various utensils due to its poor conductivity of heat and electricity.

Question 6.
Using an experiment explain how synthetic fibres are stronger than cotton fibres.
Answer:

1. Take an iron stand with a clamp.
2. Take cotton thread and synthetic threads like nylon about 50 cm in length.
3. Tie the cotton thread to the stand, so that it hangs freely from it.
4. At the free and attach a pan, so that a weight can be placed on it.
5. Add weight starting from 10 grams one by one, till the thread breaks down.
6. Note the total weight required to break the thread.
7. Repeat the same activity with synthetic thread also.
8. We can observe that more weights are required to break the synthetic thread than cotton thread.
9. Conclusion: Synthetic threads are stronger than cotton threads.

Question 7.

Answer the following questions.
i) Name the recyclabel material / materials.
ii) Name the thermosetting plastic articles.
iii) Which are thermoplastics but not to be recycled?
iv) Which are recycled but not thermosetting plastics?
Answer:
i) P.E.T bottles
ii) Electric switch, computer keyboard
iii) Polythene bag
iv) P.E.T bottle

Question 8.
Observe the following table.

Answer the following questions.
i. P.E.T is not used in the manufacture of cooker handles. Why?
ii. Which substance is used to manufacture electric switches? Why?
iii. Which is thermo plastic that can not be recycled?
iv. Why we have to ban the polythene covers?
Answer:
i) P.E.T is not used in the manufacture of cooker handles, because it is not a thermosetting plastic.
ii) Bakelite is used to manufacture electric switches, because it is thermosetting plastic.
iii) Polythene and PVC are thermoplastics that cannot be recycled.
iv) Polythene covers cannot be recycled. So, we have to ban the polythene covers.

Question 9.
Based on the smell given in the table identify the fibre and complete the table.

Answer:

Question 10.
Explain biodegradable and non-biodegradable materials with examples. Include their impact on environment.
Answer:

1. A material which is easily decomposed by natural process is called bio degradable, eg : Peels of fruits, papers, wood, cotton bags, etc.
2. A material which is not decomposed by natural process is called non-bio degradable, eg: Plastic
3. Impact on environment: Slow decomposition causes environmental pollution. The burning process of synthetic materials is also pollute the environment. This pollution causes health problems to the living things.

AP State Syllabus AP Board 8th Class Biology Important Questions Chapter 8 Production and Management of Food From Plants

AP State Syllabus 8th Class Biology Important Questions 8th Lesson Production and Management of Food From Plants

8th Class Biology 8th Lesson Production and Management of Food From Plants 1 Mark Important Questions and Answers

Question 1.
What is Agriculture?
Answer:
The process of growing crops is called Agriculture.

Question 2.
What are long term crops ? What are short term crops?
Answer:
The crops which take 180 days or more for harvesting are called long term crops.
Ex: jowar, red gram etc.
The crops which takes 100 days for harvesting are called short term crops.
Ex: green gram, black gram etc.

Question 3.
What are Kharif crops?
Answer:
The crops grown in the rainy season are termed as Kharif. It starts from June to October.

Question 4.
What are Rabi crops?
Answer:
The crops grown in winter season are called Rabi. It starts from November to April.

Question 5.
When was rice cultivated?
Answer:
Rice was cultivated in the late Mesolithic period (9000 – 8000 BC) and in the Harappa cultivation (2,300 BC).

Question 6.
In which places Rice is grown as Kharif and Rabi?
Answer:
It is grown as a Kharif or a Rabi crop from Rajasthan to Arunachal Pradesh and from Kerala to Jammu and Kashmir.

Question 7.
What are the requirements for growing of paddy?
Answer:
Nature of the soil, humidity, rainfall, temperature.

Question 8.
Name the festivals that farmers celebrate.
Answer:
The sowing and transplanting is Akshaya Trithiya and harvesting associated with Pongal and Onam.

Question 9.
Name the activities that involve at the cultivation of paddy.
Answer:

1. Preparing the soil
2. Sowing the seeds
3. Applying manure
4. Facilitate water (irrigation)
5. Weeding
6. Crop harvesting
7. Storage.

Question 10.
What do farmers do to prepare the soil?
Answer:
Ploughing is done with a wooden plough and levelling will be done by using a soil plank being pulled by a pair of bullocks.

Question 11.
What is the scientific name of paddy?
Answer:
Oryza sativa which was named by Linnaeus.

Question 12.
What is the traditional good variety of rice?
Answer:
Molagolukulu is the traditional good variety which is grown in coastal areas of Nellore.

Question 13.
Name some traditional varieties of rice.
Answer:
Amrita sari, Bangaru Teega, Kolleti Kusuma, Potti Basangi, Sona Masuri.

Question 14.
Why do farmers do medication before sowing seeds?
Answer:
Medication is done to keep seeds away from the harmful microorganisms like bacteria, fungus etc.

Question 15.
What is broadcasting method?
Answer:
The method of dispersing seeds by sprinkling is called broadcasting method.

Question 16.
What is transplantation?
Answer:
When the plants grow to certain height, farmers pick out the seedlings from the plot and make bundles. These plants are sown in proper distances. This is called transplantation. (Naru etlu)

Question 17.
What is a paddy planter?
Answer:
A paddy planter is useful for farmers those who cultivate paddy in large areas, to maintain proper distance sowing the seedlings.

Question 18.
Name some pests that attack rice plants.
Answer:
Moth caterpillars, paddy beetles and their larva, paddy grasshoppers and aphids.

Question 19.
What are the appliances used to spray pesticides?
Answer:
Sprayers and dusters.

Question 20.
Name the crops that are affected by fungus.
Answer:
Wheat, paddy and sugarcane are generally affected by fungus.

Question 21.
Name the fungal disease in groundnut.
Answer:
Groundnut is attacked by a fungal disease called Tikka disease.

Question 22.
What are the symptoms of tikka disease?
Answer:
All leaves of the affected plant have powdery spots. The whole plant becomes wilted.

Question 23.
Name some diseases that affect lemon tree.
Answer:
Viral diseases, bacterial diseases, leaf miner, citrus butterfly and fungal diseases.

Question 24.
How can the pests will be controlled?
Answer:
A farmer removes the affected leaves from the plant and put them in a dump and covers with soil to control the pests.

Question 25.
How can you identify that the plant is affected by fungus?
Answer:
A fungal infection is usually seen as white, black, yellow, brown spots or a fluffy or powdery coating on leaves.

Question 26.
Name some garden pesticides.
Answer:
Garden pesticides are derived from plants like neem, tobacco and chrysanthemum are less dangerous to other living things.

Question 27.
Name some organic synthetic pesticides.
Answer:
The organic synthetic pesticides commonly used are DDT (Dichloro diphenyl trichloro ethane) BHC (Benzene Hexa Chloride), Chlordane, Endrin, Aldrin, Endosulfan and Diazinon.

Question 28.
Who wrote a book on the dangers of pesticides?
Answer:
In 1960 Rachael Carson wrote a book called ‘silent spring’ in which she wrote the dangers of pesticides.

Question 29.
How are biofertilizers formed?
Answer:
Biofertilizers are formed by decomposing plant and animal wastes.

Question 30.
Why do farmers add manure to the soil?
Answer:
If the farmer grows same type of crops in the same field every year the nutrients of the soil decrease crops do not give good yield. So, farmers add manure for healthy growth of plants.

Question 31.
Name some chemical fertilizers.
Answer:
Urea, D.A.R, superphosphate, potash,which are enriched with nitrogen, phosphorous and potash.

Question 32.
What is irrigation?
Answer:
The process of watering crop plants in the field is known as irrigation.

Question 33.
What is furrow irrigation?
Answer:
The water is allowed to enter the field through channels or furrows made between two rows of crop is furrow irrigation.

Question 34.
What is basin irrigation?
Answer:
In this method of irrigation the field is just filled with water as in the case of paddy. Canals, tanks and wells are the water sources. Farmers dig small canals from tank to fields to supply water.

Question 35.
Why is water logging harmful?
Answer:
Water logging is harmful because it does not allow the roots to breathe.

Question 36.
What is drip irrigation method?
Answer:
This method is employed when the availability of water is poor. The water reaches the plants drop by drop.

Question 37.
Why should the weeds be removed?
Answer:
The weeds compete with the primary crops for nutrients, water and light and the prime plants may not grow. Hence weeds should be removed.

Question 38.
What is harvesting?
Answer:
Collecting grains from the crop by cutting the matured plant is called harvesting.

Question 39.
Why is storage of grain is an important task?
Answer:
We do not consume the entire crop at a time. They can be damage by fungi, pests, rats and bacteria. To over come this problem farmers dry the grains in sun and store the grain in jute bags, metallic and bamboo bins.

Question 40.
What is global grain?
Answer:
Rice is the prime, most essential and important staple food crop. It is also called global grain as it is grown all countries in the world.

8th Class Biology 8th Lesson Production and Management of Food From Plants 2 Marks Important Questions and Answers

Question 1.
What is a paddy planter? What is its use?
Answer:

1. Paddy planter is the latest machine used for sowing the seedlings.
2. It is useful for large scale cultivation of paddy.
3. It is easy to maintain proper distance sowing the seedlings.
4. Paddy planter is a device which save both time and money to the farmer.

Question 2.
Arrange the sequence of events in the cultivation of paddy crop.

Answer:

Question 3.
Give different methods of irrigating a crop in the field.
Answer:

1. Lift irrigation
2. Swinging basket
3. Water wheel
4. Tube well
5. Sprinkler
6. Drip irrigation

Question 4.
Draw and write the names of diseases that affect plants.

Answer:

1. Virus in rice plant
2. Tikka disease in groundnut

Question 5.
What are the advantages of ploughing in summer?
Answer:

1. It improves the air circulation.
2. Replacing the soil layers.
3. Reduce the weeds and diseases.
4. It improves the soil health.
5. Roots are easy to penetrate in to the soil.

8th Class Biology 8th Lesson Production and Management of Food From Plants 4 Marks Important Questions and Answers

Question 1.
Collect the information from farmers about different crops and their sowing methods.
Answer:

Question 2.
Draw and label the diagram of sprouting paddy seeds.
Answer:

Question 3.
Take some paddy grains and soak them in water for one day. Take them into watch glass and sow them in soil. After that observe the radicle and plumule with the help of hand lens and draw the picture of it.
Answer:

8th Class Biology 8th Lesson Production and Management of Food From Plants Important Questions and Answers

Question 1.
Give two examples of plants that grow with transplanting (Natlu veyadam).
Answer:
Paddy, wheat, chilli.

Question 2.
A farmer cultivated cotton crop in his field. He did not get sufficient yield. Guess any four causes for it.
Answer:

1. The crops grown in the rainy season are termed as “Kharif”.
2. Kharif season is from June to October.
3. Examples for Kharif crops are paddy, sugarcane, jowar and turmeric, etc.
4. The crops that are grown only in winter season are called Rabi crops.
5. Rabi season is from October to March.
6. Examples for Rabi crops are wheat, maize, coriandrum, fenugram, barli, etc.

Question 3.
Look at the picture and answer the following questions.

a) Which type of fertilizer is this?
b) What are the chemicals present in this?
c) What does 20-5-10 indicates?
d) Is it profit or loss by using this type of fertilizers? Why?
Answer:
a) Chemical fertilizer
b) Nitrogen (N), Phosphorus (P), Potash (K)
c) 20% of Nitrogen
5% of Phosphorus
10% of Potash
d) If we use chemical fertilizers for a longer period, soil health will be damaged. So, we should not use chemical fertilizers.

Question 4.
Study the following table and answer the questions.

a) What are the diseases caused by fungi in plants?
b) What are the diseases Transmitted through air?
c) Which microorganisms cause Tikka disease of groundnut?
d) How virus transmit mosaic disease in tobacco?
Answer:
a) Red rot of sugarcane, Tikka disease of groundnut.
b) Red rot of sugarcane, citrus canker, Tikka disease of groundnut.
c) Fungus.
d) Through insects.

Question 5.
What is the similarity between sprinklers and drip irrigation?
Answer:
Sprinklers and drip – irrigation techniques are used in low water available soils. They are very useful for the farmers who are cultivating crops in dry lands. These are called as “micro – irrigation methods”.

AP State Syllabus AP Board 8th Class Biology Important Questions Chapter 3 Story of Microorganisms 1

AP State Syllabus 8th Class Biology Important Questions 3rd Lesson Story of Microorganisms 1

8th Class Biology 3rd Lesson Story of Microorganisms 1 1 Mark Important Questions and Answers

Question 1.
What are microorganisms?
Answer:
Some organisms can be seen only with the help of a microscope. Such organisms are called ‘microorganisms’.

Question 2.
Where can we find microorganisms?
Answer:
Microorganisms can found in air, water, soil and all living organisms.

Question 3.
Write the names of some groups of microorganisms.
Answer:
Bacteria, fungi, protozoa, algae are some of the groups of microorganisms.

Question 4.
What is meant by arthropods?
Answer:
Arthropods are joint legged organisms which causes the diseases like scabies.

Question 5.
Write the names of diseases which are caused by bacteria.
Answer:
Diseases like typhoid, tuberculosis (T.B.) and septicemia (blood poisoning) are caused by bacteria.

Question 6.
Mention the diseases caused by protozoans.
Answer:
Malaria, Amoebiasis, Kala Azar, Sleeping bickness are some of the diseases caused by protozoans.

Question 7.
How do we classify the groups of microorganisms?
Answer:
Basing upon the cell structure and mode of living we can classify the microbes into 6 groups.

1. Bacteria,
2. Algae,
3. Fungi,
4. Protozoans,
5. Micro orthropods and
6. Viruses.

Question 8.
What are the uses of yeast?
Answer:

1. Yeast cells are frequently used in the fermentation process of sugars.
2. Yeast is used in the preparation of cakes and buns in bakeries.

Question 9.
What is a “bread mould”?
Answer:
Rhizopus

Question 10.
Aspergillus reproduction takes place through a special structures. What are they?
Answer:
Conidiospores.

8th Class Biology 3rd Lesson Story of Microorganisms 1 2 Marks Important Questions and Answers

Question 1.
Prepare a model of any micro arthropod.
Answer:

Question 2.
What is Pencillin? Who discovered this?
Answer:

1. ‘Antibacterium’ is prepared from a fungi called Pencillium notatum. This is called Pencillin.
2. Pencillin was discovered by Dr. Alexander Flemming.

Question 3.
How do you culture protozoa?
Answer:

1. Soak hay in pond water taken in a dish.
2. Add rice powder or ‘Gangi’ to this solution.
3. Keep the dish undisturbed for 3 – 4 days.
4. You can observe several protozoans in this hay decoction.

Question 4.
How can you observe algae in your laboratory?
Answer:

1. Take 2-3 drops of greenish pond water on a slide.
2. Spread the scrapings having small stringe like bodies on the slide.
3. Cover it with a cover slip and observe it under microscope.
4. You can see algae like spirogyra, spirulina and ceratium.

Question 5.
How Microbiology helps in identifying diseases and their prevention?
Answer:

1. Microbiology plays a very vital important role in identifying the cause of diseases by the discovery of several microorganisms.
2. Microbiology helps in the preparation of diseases caused by microorganisms by the discovery of their transmission methods.

8th Class Biology 3rd Lesson Story of Microorganisms 1 4 Marks Important Questions and Answers

Question 1.
Collect different pictures of micro arthropods.
Answer:

Question 2.
Make sketches of bacterial cell.
Answer:

Question 3.
How can you grow protozoa practically in your school? Explain.
Answer:
To grow protozoa, soak hay in pond water to prepare a decoction of hay. After 3-4 days take one or two drops of hay or grass decoction and observe it under microscope. We can see different protozoans like amoeba, paramecium etc.

Question 4.
Identify the following diagram and Label parts.
Answer:

Question 5.
How do you appreciate the fact that some of the bacteria are useful to human?
Answer:
At birth, a baby’s digestive system is a sterile, undiscovered continent. Within minutes, microbes have started pouring in from every direction. They come from the birth canal, from the mother’s breast milk, from the fingertips of nurses and the lips of happy relatives.
There are also innumerable colonies of E. coli in biotechnology and microbiology labs around the world. Everyday pharmaceutical companies manipulate E. coli to produce human-growth hormone, insulin, vitamins, and even the rennet used to make cheese. Biologists use E. coli to map metabolic pathways. Scientists are even using E. coli try to understand why we age and die.
Nitro bacter, ammonifying bacteria etc., are more useful for decompositions and fixing of Nitrogen in the plants and soil.

Question 6.
Explain how microorganisms are important for maintaining of healthy soil and biodiversity.
Answer:
The soil is home to a large proportion of the world’s biodiversity. The top eight inches of soil of one acre area may contain as much as five and half tons of bacteria and fungi.
Soil organisms breakdown organic matter, making nutrients available for uptake by plants and other organisms. A gram of garden soil contains around one million fungi, such as yeasts and moulds. Bacteria and fungi play key roles in maintaining a healthy soil. They act as decomposers that break down organic materials to produce detritus and other breakdown products. Soil detritivores, like earthworms, ingest detritus and decompose it.

Question 7.
Collect the information about useful microorganisms from your school library.
Answer:

Question 8.
How do you appreciate the role of decomposers in the earth?
Answer:

1. Microorganisms are the decomposers of the earth.
2. They decompose the organic matter from plant parts and dead animals. They enrich the soil with organic matter again.
3. Thus, they maintain the soil fertility and eliminate the wastes from the earth.
4. I appreciate the role played by decomposers in scavenging the earth by decomposing the organic matter of dead bodies.

Question 9.
What are ‘bio – fertilizers’? How are they useful?
Answer:

1. Microorganisms like Bacteria, Fungi which decompose the fallen plant parts, dung and vegetable peelings into simple chemical compounds.
2. They form ‘useful manure’ to the plants since this manure is formed naturally from biological activity of microorganisms, they are called ‘bio – fertilizers’.
3. Farmers are benefited economically. They don’t need chemical fertilizers to increase the soil fertility. Hence, Bio – fertilizers are considered as “friends of farmers”.

AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 9 Electrical Conductivity of Liquids

AP State Syllabus 8th Class Physical Science Important Questions 9th Lesson Electrical Conductivity of Liquids

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids 1 Mark Important Questions and Answers

Question 1.
Why do we use LED in the tester instead of a bulb?
Answer:
LED glows even when a very weak current is passing through the circuit. Thus, it helps in testing flow of electricity in conductors when meager current is passing through the circuit.

Question 2.
Why do we use LEDs as indicators in electrical appliances?
Answer:
LEDs glow even with a very small current passing through them. So they are used as indicators in electrical appliances like mobile phones, televisions, transformers, etc. to indicate whether the device is working or not.

Question 3.
What is meant by good conductors of electricity?
Answer:
Some materials allow electric current pass through them easily. They are called good conductors of electricity.

Question 4.
What is meant by bad conductors of electricity?
Answer:
The materials that do not allow current to pass through them are called bad conductors of electricity.

Question 5.
Why distilled water is poor conductor of electricity?
Answer:
Distilled water does not dissociate easily to form ions. So there is no availability of charged particles for passage of electricity. So it behaves like a bad conductor of electricity.

Question 6.
Why water used at our homes is a good conductor of electricity?
Answer:
The water that we get from sources such as taps, hand pumps, wells and ponds is not pure like distilled water. It contains some salts and minerals dissolved in it. This makes the water used at our homes a good conductor of electricity.

Question 7.
What is electrolytic cell?
Answer:
The cell which convert chemical energy into electric energy is called electrolytic cell.

Question 8.
A child staying in a coastal region tests the drinking water and also the sea water with his tester. He finds that compass needle deflects more in the case of sea water. Can you explain the reason?
Answer:
The reason is sea water is very good conductor of electricity when compared with drinking water due to more dissolved salts.

Question 9.
Is it safe for electrician to carry out electrical repairs outdoor during heavy down pour?
Answer:
No, because it makes electrical appliance which he repairs become wet and also rainy water is good conductor of electricity due to dissolved minerals and salts. So to avoid electric shock it is advised to carry out electric repairs indoor during heavy downpour.

Question 10.
A tester is used to check conduction of electricity through two liquids labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. What is your conclusion?
Answer:
Liquid A is better conductor than liquid B.

Question 11.
When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Answer:
The solution is a good conductor of electricity and also when we dipped the tester into the solution due to chemical effect it produces electricity and it behaves like an electrolytic cell and also current carrying tester behaves like a magnet and shows deflection.

Question 12.
What is the main threat to environment from electroplating factories?
Answer:
In the electroplating factories the disposal of the used conducting solution is a major concern. It is a polluting waste. So it is the main threat to environment from electroplating factories.

Question 13.
Why should we have to deposit nickel or chromium on iron?
Answer:
Iron which is easily corroded by atmospheric air, moisture and carbon dioxide are coated with deposits of nickel or chromium which are most resistant to such corrosion.

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids 2 Marks Important Questions and Answers

Question 1.
What is the name given to wires attached to LED. How these wires are connected to a battery?
Answer:
There are two wires called leads attached to an LED. One lead is slightly longer than other.

While connecting to the LED to the circuit, the longer lead is always connected to the positive terminal of the battery and the short lead connected to the negative terminal of the battery.

Question 2.
What are the requirements for fine coating in electroplating process?
Answer:

1. The object to be electroplated should be free from greasy matter.
2. The surface of the article should be rough so that the metal deposited sticks permanently.
3. The concentration of the electrolyte should be so adjusted as to get smooth coating.
4. Current must be the same throughout.

Question 3.
Answer the following questions.
a) When we pass current through a copper sulphate solution having copper plate and iron key connected to a battery and tap key in series by closing tap key. What is deposit on iron key?
b) If the key is to be coated with zinc or aluminium instead of copper, what changes do we need to make the above experiments?
Answer:
a) There is red mass of copper deposited on iron key.
b) If we want to coat aluminium or zinc or iron then, we have to take electrolyte is like aluminium sulphate or zinc sulphate and the positive electrode is aluminium or zinc.

Question 4.
Name three liquids which when tested in the manner shown in figure may cause the magnetic needle to deflect.
Answer:
In order to deflect the needle the liquid must be a good conductor of electricity. So we have to take liquids like lemon juice, vinegar solution, salt solution.

Question 5.
The bulb does not glow in the set up shown in figure. List the possible reasons. Explain your answer.
Answer:

1. The wires are not properly connected so the circuit may be open.
2. The liquid taken in the vessel may be a bad conductor of electricity which does not allowing the passage of current.

Question 6.
Give two examples for electrolyte.
Answer:
Electrolyte is a solution of substance through which current can pass. The examples of electrolyte solutions are NaC/ solution, CaCl₂ solution.

Question 7.
If the key is to be coated with aluminium instead of copper,what changes do we need to make in the experiment of coating on iron key with copper?
Answer:
Changes we need to make are:

1. Anode should be aluminium.
2. The electrolyte solution must be salt solution of aluminium that is aluminium chloride or aluminium sulphate solutions.

Question 8.
Is plastic coated by the process of electroplating? Why?
Answer:
No. Plastic cannot be coated on a metal by using electroplating. Plastic does not act as an electrolyte. So electrolysis process is not possible with plastic which is main criteria for electroplating. So plastic cannot be coated on a metal by the process of electroplating.

Question 9
What are the requirements for fine coating in electroplating process?
Answer:

1. The object to be electroplated should be free from greasy matter.
2. The surface of the article should be rough so that the metal deposited sticks permanently.
3. The concentration of the electrolyte should be so adjusted as to get smooth coating.
4. Current must be the same throughout.

Question 10.
In case of a fire, before the fire men use the water, they shut off the main electrical supply for the area. Explain why they do this.
Answer:
Fire men use water to put out fire. Water containing dissolved salts is a good conduc¬tor of electricity. If fire men pour water on fire the electrical appliances near the fire may be wet if anybody touches those appliances they may have electric shock. In order to avoid people to get electric shock due to wet electrical appliances the fire men shut off electrical supply before they use water.

Question 11.
We get some items made from iron wire in which iron wire is coated with plastic. Is plastic coated by the process of electroplating? Why can plastic not be coated on a metal by the process of electroplating?
Answer:
No. Plastic cannot be coated on a metal by using electroplating. The reason is plastic being a carbon polymer does not dissociate into ions. So it does not allow passage of current. So it does not act as an electrolyte. So electrolysis process is not possible with plastic which is main criteria for electroplating. So plastic cannot be coated on a metal by the process of electroplating.

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids 4 Marks Important Questions and Answers

Question 1.
Prepare a table having various material used at home classifying as good conductors or poor conductors and their use.
Answer:

Question 2.
What are the uses of electrolysis in daily life?
Answer:
The uses of electrolysis:

1. Electroplating: To avoid rusting of iron it is coated with nickel or chromium by electrolysis.
2. Gold covering works: Ornaments made of cheap metal like copper can be coated with gold using electrolysis.
3. Metallurgy: Pure metals can be extracted from minerals and ores using electrolysis.
4. Electrolysis: It is used in electrical printing and to produce gramphone records.

Question 3.
Collect the information from various sources on the applications of electroplating in daily life and prepare a note on that.
Answer:
Uses of electroplating:

1. Metals like iron are coated with deposits of nickel or chromium to prevent rusting.
2. Machinery parts are often chromium plated to protect them from corrosion and at the same time to give them good polish.
3. Electroplating is also used in repairing worn out parts of machinery.
4. Electroplating is also done for ornamentation and decoration purposes.
5. Processed food items are preserved in tin coated iron cans by electroplating method.
6. Zinc coated iron by electroplating method is used for bridges and in automobiles.

Question 4.
Test the conductivity of liquids given below and fill the table.

Answer:

Question 5.
Why does chromium is used for electroplating? Why the objects which have chromium plated are not made of chromium itself?
Answer:

1. Chromium has a shiny appearance does not corrode and resist scratches.
2. However chromium is expensive and may not be possible to make the whole object out of chromium.
3. So the object is made from a cheaper metal and only a coating of chromium is done over it.

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids Important Questions and Answers

Question 1.
Name the process of coating a metal on another metal. Draw a neat diagram related to this process. Label the parts.
Answer:
The process which is used to coating a metal on another metal is called “electroplating”.

Question 2.
Draw a diagram shows electroplating process. Write any one of the requirements for the fine coating.
Answer:

1. The object to be electroplated should be free from greasy matter.
   
2. The surface of the article should be rough so that the metal deposited sticks permanently.
3. The concentration of the electrolyte should be so adjusted as to get smooth coating.
4. Current must be the same throughout.

AP State Syllabus AP Board 8th Class Biology Important Questions Chapter 2 Cell: The Basic Unit of Life

AP State Syllabus 8th Class Biology Important Questions 2nd Lesson Cell: The Basic Unit of Life

8th Class Biology 2nd Lesson Cell: The Basic Unit of Life 1 Mark Important Questions and Answers

Question 1.
Who discovered cell first time?
Answer:
It was the year 1665 Robert Hooke, a British scientist discovered the cell.

Question 2.
Which part of cell contains cell organelles?
Answer:
The jelly like substance between the nucleus and cell membrane is called cytoplasm. It is a heterogeneous material. It contains membrane bound structures called cell organelles.

Question 3.
What is the difference between cells in onion peel and cells in Spinach?
Answer:
Cells in onion peel arranged systematically with prominent nucleus. Cells in spinach are in different sizes and shapes without nucleus to perform nutrition.

Question 4.
Make different questions to know cells and cell organelles.
Answer:

1. What are the structures present in the cells?
2. Why cells are considered to be structural and functional unit of life?

Question 5.
Prepare different questions to know the discovery of cell.
Answer:

1. In which year cell discovered?
2. Name the scientist who observed cells.

Question 6.
What is staining?
Answer:
The process of using colouring agents in order to highlight particular areas in the cell is called staining.

Question 7.
What is ‘magnification’?
Answer:
Amount of increase in apparent size of a thing more time than its normal size to visualise is called magnification.

Question 8.
What are Unicellular Organisms? Give examples.
Answer:
The organisms survive its life with a single cell are called unicellular organisms.
Ex : Amoeba, Chlamydomonas, etc.

Question 9.
What is the meaning of ‘Cell’ in Latin?
Answer:
In Latin ‘cell’ means ‘A little room’.

8th Class Biology 2nd Lesson Cell: The Basic Unit of Life 2 Marks Important Questions and Answers

Question 1.
“Cell wall is essential in plant cells” – Why?
Answer:

1. Cell wall gives mechanical strength.
2. Without the cell wall, a plant can not stand errect.
3. Cell wall helps the plant cells when they are turgid.

Question 2.
What is the significance of cover slip in your preparation of slides?
Answer:

1. Cover slip protects the material under study from coming in contact with the lens of the microscope.
2. It presses upon the material keeping it plane.

Question 3.
How do you appreciate the role of microscope in the study of cell?
Answer:

1. The microscope is very useful instrument in the study of cells.
2. Scientists use electron microscope for their study which can help to see upto a millionth of a meter.
3. I will appreciate the role of microscope in the growth and development of science and human welfare.

8th Class Biology 2nd Lesson Cell: The Basic Unit of Life 4 Marks Important Questions and Answers

Question 1.
Observe the permanent slides of human body cells in your school. Collect the data in a tabular form.
Answer:

AP State Syllabus AP Board 8th Class Biology Important Questions Chapter 7 Different Ecosystems

AP State Syllabus 8th Class Biology Important Questions 7th Lesson Different Ecosystems

8th Class Biology 7th Lesson Different Ecosystems 1 Mark Important Questions and Answers

Question 1.
Who coined the word ecosystem at first?
Answer:
The word ecosystem was coined by a British Botanist A.G. Tansley in 1935.

Question 2.
What are the different terms used for environment?
Answer:
The different terms are habitat, biome, ecological systems.

Question 3.
What do we call the small level of ecosystem?
Answer:
The small level of ecosystem is called habitat.

Question 4.
What do we call the larger level of ecosystem?
Answer:
The larger level of ecosystem is called Biome.

Question 5.
What do we study in an ecosystem?
Answer:
In ecosystem we study about the changes occuring in the habitat like organisms moving away from the habitat or entering the habitat.

Question 6.
How is an ecosystem made up of?
Answer:
An ecosystem is made up of groups of living organisms and their environment.

Question 7.
Name the biotic and the abiotic components.
Answer:
The living things like plants,animals and microorganisms are known as biotic components. Soil, water, sunlight, air, etc. are known as abiotic components.

Question 8.
What type of relationship is seen in an ecosystem?
Answer:
There is a feeding relationship between plants and animals.

Question 9.
How do plants and animals depend on one another?
Answer:
There is an interdependence between plants and animals for space, reproduction, shelter etc.

Question 10.
From where do all living things derive energy?
Answer:
All living things derive energy from sun.

Question 11.
Why are decomposers called recyclers?
Answer:
Decomposers return nutrients to the soil by decompose the dead plants and animals for the plants to use, as the cycle begins again, so they are called recyclers.

Question 12.
Where does the food web start from?
Answer:
The food web starts from the Producers.

Question 13.
What happens when plants and animals die in a food web?
Answer:
When plants and animals die in a food web, they are decayed and decomposed by decomposers like bacteria and fungi.

Question 14.
How do the changes take place in an ecosystem?
Answer:
Powerful storms, tsunami etc., destroy ecosystem and the changes take place in an ecosystem.

Question 15.
What are mangroves?
Answer:
Mangroves are one of the most productive ecosystems, deriving nourishment from terrestrial fresh water and tidal salt water.

Question 16.
Where do mangroves grow?
Answer:
Mangrove forests grow in back waters low depth areas of sea shores.

Question 17.
Where is Coringa Mangrove situated?
Answer:
Coringa Mangrove is situated South of Kakinada Bay and is about 150 km South of Visakhapatnam.

Question 18.
From which rivers C&ringa mangrove receives water?
Answer:
Coringa mangrove receives fresh water from Coringa river and Gaderu river, tributories of Gautami Godavari river.

Question 19.
Name the producers present in Coringa mangrove.
Answer:
Mangrove, spirogyra, euglena, oscilatoria, blue green algae, ulothrix etc.

Question 20.
Name the consumers present in Coringa.
Answer:
Shrimp, crab, hydra, protozoans, mussel, snails, turtle, daphnia, brittle word, tube worm, etc.

Question 21.
Name the decomposers present in Coringa.
Answer:
Detritus feeding bacteria etc.

Question 22.
In what conditions a living community lives?
Answer:
A living community lives in an environment which supplies its materials and energy requirements and provides other living conditions.

Question 23.
What is ecosystem?
Answer:
The living community together with the physical environment forms an interacting system called the ecosystem.

Question 24.
How much place is occupied by the desert on land?
Answer:
The desert occupy about 11% of the land and occur in the regions with an average rainfall of less than 23 mm per year.

Question 25.
What type of producers can be seen in deserts?
Answer:
The shrubs, bushes, grasses and some trees.

Question 26.
Why do cacti have succulent stems?
Answer:
They store water in their stems to be used during the time of water scarcity.

Question 27.
Which organisms capture energy from sun?
Answer:
The energy from the sun is captured by plants and is stored in the form of potential energy in food stuffs.

Question 28.
What are the first trophic level in the ecosystem?
Answer:
Plants are the producers and represent the first trophic level in the ecosystem.

Question 29.
What does the food chain consist of?
Answer:
The food chain consists of four steps – the producers, primary consumers, secondary consumers and tertiary consumers.

Question 30.
What are consumers? Give examples.
Answer:
The organisms which eat other living things and get their energy from them are called consumers. Ex: Animals.

Question 31.
What are decomposers? Give examples.
Answer:
The organisms which feed on wastes, debris of plants and animals or on their remains after they die. Ex : Microorganisms.

Question 32.
What is a food web?
Answer:
A food web consists of several inter linked food chains and each organism in a food web will be a member of more than one food chain.

Question 33.
What are producers? Give examples,
Answer:
Plants are the only organisms capable of carrying out photosynthesis and producing food to all living organisms in any ecosystem. For this reason plants are called Producers.

8th Class Biology 7th Lesson Different Ecosystems 2 Marks Important Questions and Answers

Question 1.
Complete this flow chart.

Answer:

1. Terrestrial
2. Aquatic
3. Aquarium, Terrarium, Spaceship
4. Grassland ecosystem
5. Forest Ecosystem
6. Desert ecosystem
7. Fresh water ecosystem
8. Marine water ecosystem
9. Mangrove ecosystem

Question 2.
What is the significance of mangrove ecosystem?
Answer:

1. Mangroves serve as important breeding grounds for a variety of commercially important organisms.
2. They also serve as protective areas for endangered species.
   Example: Coringa Mangrove Is situated South of Kakinada and is about 150 Km South of Vizag.

8th Class Biology 7th Lesson Different Ecosystems 4 Marks Important Questions and Answers

Question 1.
“The Sun is the malm source of energy for all laving things on earth”. How?
Answer:

1. All the organisms in an ecosystem derive energy from food to live.
2. Plants trap the solar energy through photosynthesis. They convert the light energy into chemical energy.
3. Animals do not get energy directly from Sun. Many animals eat plants, however which use Sunlight to make food.
4. Carnivores do not eat plants still depend on the energy of the sunlight as they eat other plant eaters.

Question 2.
Draw and label the plants and animals present in the food web in Coringa Ecosystem.
Answer:
Diagram of the food web in Coringa Ecosystem.

Question 3.
Draw the diagram showing figure of energy flow in an ecosystem. (Annexure)
Answer:
Energy flow in an ecosystem.

Question 4.
Classify the ecosystem on different basis. (OR)
Draw the flow chart showing different types of ecosystems. Who coined the term ecosystem?
Answer:

1. Ecosystem can vary from a small plant to a dense forest. Ecologists classified ecosystem on different basis.
2. Some such classifications are – artificial and natural temporary and permanent.
3. Due to Abiotic factors, different ecosystems develop in different ways.

Flow chart of classification of ecosystem

The term “Ecosystem” was coined by A.G. Tansley.

Question 5.
Prepare a table what are the adaptations of the desert animal take the data from your school library.
Answer:

Question 6.
Construct the food web with the following.
Grass → Plants → Grasshopper → Frog → Snake → Eagle → Goaf → Fox → Tiger → Wolf → Rabit.
Answer:

8th Class Biology 7th Lesson Different Ecosystems Important Questions and Answers

Question 1.

Shown here is a food chain, classify each organism in the food chain as producer, primary consumer, secondary consumer or tertiary consumer.
Answer:
In the above food chain

1. Leaf – producer
2. Catterpillar – primary consumer
3. Chameleon – secondary consumer
4. Snake – tertiary consumer
5. Eagle – top carnivore

Question 2.
Read the following paragraph and answer the questions given below.
Several plants, algae, etc. use sunlight to make their own food are called producers. Consumers feed on producers to get energy. The last level is made of decomposers. They feed on wastes, debris of plants and animals or on their remains after they die. They are called Recyclers also.

1. Which are the producers in the food web? Why are they called producers?
2. What are consumers? Give some examples.
3. What are recyclers? Why are they called so? Give some examples.
4. How many levels should be there in a food chain? What are they?

Answer:

1. Algae and plants are the producers in the given food web. They convert the solar energy into chemical energy through a process called photosynthesis.
2. The animals which feed on these producers (plants) are called primary consumers. Ex : Deer, Grasshopper, Rabbit.
3. Saprophytic bacteria and fungi are act as decomposers. They feed on dead plants and animals. They decompose these dead bodies and convert them into minerals. So, they are called ‘reproducers’.
4. Food chain consists of 4 trophic levels.
   They are 1) producers 2) primary consumers 3) secondary consumers and 4) tertiary consumers.

Question 3.
The desert occupy about 17% of the land and occur in the regions with an average rainfall of less than 23 mm per year. Due to extremes of temperature, the species composition of desert ecosystem is much varied and typical.
a) Which type of adaptations do desert animals have?
b) Write the adaptations in the desert plants.
c) Why the camel is called ship of the desert?
d) In deserts variations of animals is very less. Why?
Answer:
a) They have adaptations to prevent water loss from extreme temperatures.
b) Xerophytic plants do not have stomata. So, they prevent water loss.
c) Camel is called “desert ship” because it has so many adaptations to travel in desert.
d) Due to extremes of temperature, the species composition of desert ecosystem is varied and typical.