Class 8

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

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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:

Good conductors	Bad conductors
1) Metals	1) Wood
2) Acid solutions	2) Plastic
3) Base solutions	3) Diamond
4) Salt solutions	4) Distilled Water

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.

Object	Material	Bulb glows Yes/No	Good conductor/ bad or poor conductor
Nail	Iron	Yes	Good conductor
Eraser	Rubber	No	Bad or poor conductor
Paper	Cellulose	No	Bad or poor conductor
Chalk	Calcium carbonate	No	Bad or poor conductor
Straw	Plastic	No	Bad or poor conductor
Plastic	Plastic	No	Bad or poor conductor
Matchstick	Wood	No	Bad or poor conductor

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.

Liquid	LED glows	Good conductor/ poor or bad conductor
Distilled water	No	Bad conductor
Drinking water	Yes	Good conductor
Coconut oil	No	Bad conductor
Lemon juice	Yes	Good conductor
Vinegar	Yes	Good conductor
Kerosene	No	Bad conductor
Vegetable oil	No	Bad conductor
Sugar solution	No	Bad conductor
Common salt solution	Yes	Good conductor
Milk	No	Bad conductor

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.

Material ‘	Does the LED glow? Yes/No	Good conductor/bad conductor
Distilled water	No	Bad conductor
Distilled water + salt	Yes	Good conductor
Distilled water + CuSO4	Yes	Good conductor
Distilled water + lemon juice	Yes	Good conductor

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:

Thermoplastics	Thermosetting plastics
Plastics which get deformed easily on heating and can be bent are known as thermoplastics. Ex: PVC, polythene bags, toys, combs, etc.	Plastics which moulded once can’t be softened by heating are called thermo­setting plastics. Ex : Bakelite and melamine.

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:

Material	Biodegradable/non-biodegradable
1. paper	Biodegradable
2. wood	Biodegradable
3. metals	Non-biodegradable
4. cotton cloth	Biodegradable
5. plastic container	Non-biodegradable
6. woolen sweater	Biodegradable
7. peels of vegetable and fruit	Biodegradable

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.

Smell on burning	Name of the fibre
If it smells like burning hair
If it smells like burning paper
If the yarn melts

Answer:

Smell on burning	Name of the fibre
If it smells like burning hair	Wool (or) Silk
If it smells like burning paper	Cotton
If the yarn melts	Polyester (or) nylon

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.

Name of the plant disease	Causative Microorganism	Mode of Transmission
Tobacco mosaic	Virus	Insects
Red rot of sugarcane	Fungi	Air, seedlings
Citrus canker	Bacteria	Air
Tikka disease of groundnut	Fungi	Air, seeds

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:

Name of the microorganism	Utility
Yeast(Fungus)	Production of alcohol fermented foods like Idli, Dosa etc………..
Pencillium notatum (Fungus)	Preparation of antibiotics
Nostoc, Anabina, Azatobactor	Fixation of atmospheric nitrogen.
Spirulina	Preparation of medicines
Lactobacillus	Preparation of curd, cheese, buttermilk.

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:

Material used at home	Good conductor/ poor conductor	Use
1) Copper	Good conductor	Wires, electrical appliances
2) Iron	Good conductor	Electrical wires, electrical appliances
3) Aluminium	Good conductor	Wires, electrical appliances
4) Plastic	Poor conductor	Handles of electrical appliances, electrical insulating material
5) Wood	Poor conductor	Handles of electrical appliances

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.

Material	Compass needle show deflection Yes / No	Conductor / Insulator
Lemon juice
Honey
Milk
Vinegar
Tap water
Vegetable oil

Answer:

Material	Compass needle show deflection Yes / No	Conductor / Insulator
Lemon juice	Yes	Conductor
Honey	No	Insulator
Milk	No	Insulator
Vinegar	Yes	Conductor
Tap water	Yes	Conductor
Vegetable oil	No	Insulator

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:

Name of the cell	Shape of the cell	Name of the parts
Muscle cell	Spindle shaped, short, elongated	Nucleus, cell membrane, cytoplasm.
RBC	Concave on both sides, sometimes round	Nucleus, cell membrane, cytoplasm.
Nerve cell	Long having processes	Nucleus, cell membrane, cytoplasm
White Blood Cell (WBC)	Amoeboid shape	Nucleus, cell membrane, cytoplasm, granules

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.

AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 8 Combustion, Fuels and Flame

AP State Syllabus 8th Class Physical Science Important Questions 8th Lesson Combustion, Fuels and Flame

8th Class Physical Science 8th Lesson Combustion, Fuels and Flame 1 Mark Important Questions and Answers

Question 1.
What do you mean by combustion?
Answer:
A chemical process in which a material reacts with oxygen present in air to generate heat is called combustion.

Question 2.
What is ignition temperature?
Answer:
The lowest temperature at which a substance catches fire is called ignition temperature.

Question 3.
What are inflammable substances? Give examples.
Answer:
The substance which have very low ignition temperature easily catch fire are called inflammable substances, e.g.: Petrol, alcohol, LPG, etc.

Question 4.
What is explosion?
Answer:
A chemical reaction takes place with the evolution of heat, light, sound and large amount of gas is called explosion.

Question 5.
What is calorific value? What is its unit?
Answer:
Calorific value of a fuel is the amount of heat energy produced on complete combustion of 1 kg of that fuel.
It is measured in kilo joules per kg. (kJ/kg)

Question 6.
Which zone of a flame does a goldsmith use for melting gold and silver and why?
Answer:
The goldsmith would use outermost zone for melting gold and silver because it is hottest zone due to complete combustion.

Question 7.
Explain how CO₂ is able to control fires?
Answer:
When CO₂ released from the cylinder on fire, it expands enormously in volume and cools down. So, it is not only forms a blanket around fire, it also brings down the temperature of fuel. That is why it is an excellent fire extinguisher.

Question 8.
Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not ?
Answer:
When you heat a piece of paper wrapped around an aluminium pipe the heat is taken up by aluminium pipe so the paper does not reach its ignition temperature.

Question 9.
Can the process of rusting be called combustion? Discuss.
Answer:
Rusting of Iron is a combustion reaction. Combustion is a process in which elements combine with oxygen. During formation of rust iron atoms combine oxygen in the air forming iron oxides or rust.

Question 10.
Name the products formed when a candle burns in air.
Answer:
The products formed are carbondioxide and water because wax is mixture of hydrocarbons.

8th Class Physical Science 8th Lesson Combustion, Fuels and Flame 2 Marks Important Questions and Answers

Question 1.
What are combustible and non combustible materials and give examples for them?
Answer:
Combustible materials:
The materials which burn when brought near a flame are called combustible materials, e.g. : Petrol, diesel, kerosene, etc.
Non-combustible materials:
The materials which do not burn when brought near a flame are called non-combustible materials, e.g.: Pebbles, sand, clay, iron, etc.

Question 2.
What are the different types of combustion and define them?
Answer:
Combustion is two types.

1. Spontaneous combustion:
   The type of combustion in which material suddenly bursts into flames without the application of apparent cause is called spontaneous combustion.
2. Rapid combustion:
   The type of combustion in which materials burns rapidly and produce heat and light is called rapid combustion.

Question 3.
What are the different zones present in a candles and what are the colours of those zones?
Answer:
There are three zones in a candle.

1. Outermost zone: This is the hottest part which is in blue colour.
2. Middle zone: This is moderately hot part which is in yellow colour.
3. Dark zone: This is least hot part which is in black colour.

Question 4.
In an experiment 4.5 kg of a fuel was completely burnt. The heat produced was measured to be 1,80,000 KJ. Calculate the calorific value of fuel?
Answer: The mass of fuel = 4.5 kg
The heat produced = 1,80,000 KJ
heat produced 1,80,000
The calorific value of fuel = \(\frac{\text { heat produced }}{\text { mass of the fuel }}\) = \(\frac{1,80,000}{4.5}\) = 40,000 KJ/Kg
mass of the fuel 4.5

Question 5.
LPG is better domestic fuel than wood?
Answer:

1. On burning wood it produces lot of smoke and also complete burning does not takes place whereas LPG undergo complete combustion so does not produce smoke.
2. Due to incomplete combustion wood produce harmful gas like carbon monoxide whereas LPG does not produce carbon monoxide.
3. Wood has high ignition temperature so does not burn immediately whereas LPG has low ignition temperature burns easily.

Question 6.
How do you appreciate use of fossil fuels in daily life?
Answer:
We are depend upon fossil fuels for our daily needs like cooking, transportation, running machinery and producing electricity, etc. Everywhere we go there is use of fossil fuel. Without fossil/fuels we may be in stone age. So the use of fossil fuels in daily life should be thoroughly appreciated.

Question 7.
What would happen if oxygen stops to support combustion? – Make a guess. And if it is the situation for what other fuels are useful?
Answer:
If oxygen stops to support combustion there is no other gas which will support combustion. Then fossil fuels are not useful in producing heat, energy and electricity.
So we should have to prefer alternative sources of energy like solar energy, wind energy, tidal energy, biomass energy, geothermal energy, etc. for our energy needs.

Question 8.
Let us assume that you are on the moon. If you try to focus sun light on a paper using magnifying glass, does the paper catch fire? or not? Why?
Answer:
No, moon reflects entire sunlight that falls on the surface because it acts as perfect reflector. Whereas earth is also acts as reflector but green house gases present in atmosphere absorbing the sunlight and resending on earth. So paper can be burnt on earth by using magnifying glass but it is not possible on moon.

Question 9.
Why does tap water is not used to control fire involving electrical equipment ?
Answer:

1. Tap water cannot be used to control the fire involving electric equipment because it is a good conductor of electricity.
2. It conducts electricity resulting in electrical shock to the user.

Question 10.
Explain how carbon dioxide is able to control fires.
Answer:
Carbon dioxide, being heavier than oxygen, covers the fire like blanket and also brings down the temperature of fuel. Since the contact between the fuel and oxygen is cut off the fire comes under control.

8th Class Physical Science 8th Lesson Combustion, Fuels and Flame 4 Marks Important Questions and Answers

Question 1.
How does candle works?
Answer:

1. A candle is mainly a source of light and heat.
2. A candle is made of wax in which a thick thread inserted wax in the candle melts when it is lighted by a match stick.
3. A little of wax forms vapour.
4. This vapour combines with oxygen in the air to form flame.
5. The heat of the flame melts more of the wax from the top of the candle.
6. The melted liquid wax moves upward through the thread. It also changes to vapour when it reaches the top of the wick and byrns with the flame.

8th Class Physical Science 8th Lesson Combustion, Fuels and Flame Important Questions and Answers

Question 1.
Spirit burns quickly like petrol but sodium metal and white phosphorous burns without any ignition.
Complete the following table and rewrite it in the table.

Rapid combustible substances	Spontaneous combustible substances

Answer:

Rapid combustible substances	Spontaneous combustible substances
1)  Material burns rapidly and produce heat and light. 2)   Spirit burns quickly. 3)   Petrol burns quickly.	1)  Material suddenly bursts into flames without the application of apparent cause. 2)   Sodium burns without any ignition. 3)   Phosphorous burns without any ignition.

Question 2.

Fuel	Calorific Value (K.J / Kg)
Cow dung	6,000 – 8,000
Coal	25,000 – 30,000
Petrol, Diesel	45,000
LPG	55,000
Hydrogen	1,50,000

Answer the following questions.
i) Name the fuel having highest calorific value.
ii) How much heat energy is released when one kg of petrol burnt?
iii) Name two fuels which causes less pollution.
iv) Mention any one of the alternate energy source which is not mentioned in the above table.
Answer:
i) Hydrogen
ii) 45,000 Kilo Joules
iii) Hydrogen, L.P.G
iv) Solar power, Gobar gas, Wind power, Bio-diesel.

AP State Syllabus 8th Class Maths Solutions 5th Lesson Comparing Quantities Using Proportion InText Questions

AP State Syllabus AP Board 8th Class Maths Solutions Chapter 5 Comparing Quantities Using Proportion InText Questions and Answers.

8th Class Maths 5th Lesson Comparing Quantities Using Proportion InText Questions and Answers

Do this

Question 1.
How much compound interest is earned by investing Rs. 20000 for 6 years at 5% per annum compounded annually? (Page No. 114)
Answer:
P = Rs. 20,000; R = 5%; n = 6 years

∴ Compound Interest = Amount – Principal = 26802 – 20,000
∴ C.I. = Rs. 6802 /-

Question 2.
Find compound interest on Rs. 12600 for 2 years at 10% per annum compounded annually.    (Page No. 114)
Answer:
P = Rs. 12,600; R = 10%; n = 2 years

∴ Compound Interest = Amount – Principal = 15,246 – 12,600
∴ C.I. = Rs. 2646 /-

Question 3.
Find the number of conversion times the interest is compounded and rate for each.
i) A sum taken for 1\(\frac{1}{2}\) years at 8% per annum is compounded half yearly.
ii) A sum taken for 2 years at 4% per annum is compounded half yearly.     (Page No. 115)
Answer:
Compound interest will be calculated for every 6 months.
There will be 3 periods in 1\(\frac{1}{2}\) year.
∴ n = 3
∴ Rate of interest for half yearly = \(\frac{1}{2}\) × 8% = 4%
∴ R = 4%; n = 3
ii) C.I. should be calculated for every 6 months.
There will be 4 time periods in 2 years.
∴ n = 4
∴ Rate of interest for half yearly = \(\frac{1}{2}\) × 4% = 2%
∴ n = 4 ; R = 2%

Try These

Question 1.
Find the ratio of gear of your bicycle.       (Page No. 96)

Count the number of teeth on the chain wheel and the number of teeth for the sprocket wheel.
{number of teeth on the chain wheel} : {number of teeth of sprocket wheel}
This is called gear ratio. Write how many times sprocket wheel turns for every time the chain wheel rotates once.
Answer:
The ratio between the rotations of chain wheel and sprocket wheel is 4 : 1.

Question 2.
Collect newspaper cuttings related to percentages of any five different situations.  (Page No. 96)
Answer:
1) Bharti to sell 5% stake for $ 1.2b:
New Delhi, May 3: The country’s largest telecom operator Bharti Airtel said on Friday that it will sell 5 per cent stake to Doha – based Qatar Foundation Endowment (QFE) for $1.26 billion (Rs. 6,796 crores) to fund its future growth plans.
The deal will bring cash for the company at a time when its balance sheet is stretched and there is threat of Bharti Airtel having to pay hefty fees to regulatory authorities as government is re-looking at past policies.

2) Indian Firms Mop – Up Down By 36% In FY13:
New Delhi: Indian companies raised nearly Rs. 31,000 crore from the public issuance of equity and debt in 2012 – 13, a slump of 36 per cent from the preceding year.
According to latest data available with market regulator Sebi (Securities and Exchange Board of India), a total of Rs. 30,859 crore worth of fresh capital were mopped – up from equity and debt market during 2012 – 13, which was way below than Rs. 48,468 crore garnered in 2011 -12. Going by the statistics, it was mostly debt market that was leveraged to meet the funding requirements of businesses in the past fiscal as compared to capital raised through sale of shares through instruments like initial public offering (IPO) and rights issue. A total of Rs. 15,386 crore were raised from the debt market via 11 issues in 2012 – 13, much lower than Rs. 35,611 crore garnered through 20 issues in the preceding fiscal.

3) IT – ITeS sector employs 2.97m people in FY13:
New Delhi: The total number of professionals working in India’s $100 billion IT – information technology enabled services (IT – ITeS) sector grew by 7 per cent to 2.97 million in the last fiscal, Parliament was informed on Friday.
The IT – ITeS sector, which contributes about 8 per cent to the country’s economy, provided employment to 2.77 million professionals in 2011 -12 fiscal, minister of state for communications and IT Milind Deora said. “The Indian IT – ITeS industry has been progressively growing and is able to secure new projects from various foreign coun¬tries,” Mr Deora said. During the 2012 -13 fiscal, 6,40,000 professionals were employed in the domestic market.

4) For RBI, it’s not all is well yet:
Slashes repo rate by 0.25%; rules out any more cuts; raises red flag on CAD DC Correspondent Mumbai, May 3:
The RBI cut the repo rate (rate at which it lends to banks) by a quarter per cent on Friday to 7.25 per cent from 7.75 per cent, but this will not be passed on to the consumers by way of lower personal loans for housing etc., immediately according to bankers.
It also raised the growth rate from 5.2 per cent projected in January to 5.7 per cent for 2013 -14 and lowered the inflation rate to 5.5 per cent for the year.
RBI governor Dr D. Subbarao said based on the current and prospective assessment of various economic factors and the dismal 4.5 per cent lowest growth rate in the last quarter, it was decided to cut the policy rate by 25 basis points.

5) Markets sink on RBI’s Bearish outlook on rate:
DC Correspondent Mumbai, May 3:
In a highly volatile trading session, the markets retreated from their three month high led by interest rate sensitive banking, auto and real estate sector stocks after the Reserve Bank of India (RBI) cautioned that the room for further monetary policy easing is limited.
The Sensex closed 19,575.64, sliding 160.13 points or 0.81 per cent while the Nifty dropped 55.35 points or 0.92 per cent to end the week at 5,944.

Question 3.
Find the compound ratios of the following. (Page No. 99)
a) 3 : 4 and 2 : 3
b) 4 : 5 and 4 : 5
c) 5 : 7 and 2 : 9
Answer:
Compound ratio of a : b and c : d is ac : bd.

Question 4.
Give examples for compound ratio from daily life.     (Page No. 99)
Answer:
Examples for compound ratio from daily life:
i) To compare the ratio of tickets of 8th class students (Boys & Girls) is 3:4 and the ratio of tickets of 7th class students is 4 : 5.
ii) The comparision between two situations is 4 men can do a piece of work in 12 days, the same work 6 men can do in 8 days.
iii) Time – distance – speed.
iv) Men – days – their capacities etc.

Question 5.
Fill the selling price for each.     (Page No. 104)

Answer:

Question 6.
i) Estimate 20% of Rs. 357.30 ii) Estimate 15% of Rs. 375.50      (Page No. 105)
Answer:

ii) 15% of 375.50 = \(\frac{15}{100}\) × 375.50 = 15 × 3.7550 = Rs. 56.325

Question 7.
Complete the table.     (Page No. 105)

Answer:

Think, discuss and write

Question 1.
Two times a number is 100% increase in the number. If we take half the number what would be the decrease in percent?    (Page No. 101)
Answer:
Increase percent of 2 times of a number = \(\frac{(2-1)}{1}\) × 100 = 1 × 100 = 100%
Half of the number = 1 – \(\frac{1}{2}\) = \(\frac{1}{2}\)
Decrease in percent = \(\frac{\frac{1}{2}}{1}\) × 100 = \(\frac{1}{2}\) × 100 = 50%

Question 2.
By what percent is Rs. 2000 less than Rs. 2400? Is it the same as the percent by which Rs. 2400 is more than Rs. 2000? (Page No. 101)
Answer:
Decrease in percent of Rs. 2000 less than Rs. 2400

Increase in percent of Rs. 2400 more than Rs. 2000

Question 3.
Preethi went to a shop to buy a dress. Its marked price is Rs. 2500. Shop owner gave 5% discount on it. On further insistence, he gave 3% more discount. What will be the final discount she obtained? Will it be equal to a single discount of 8%? Think, discuss with your friends and write it in your notebook. (Page No. 105)
Answer:
Marked price of a dress selected by Preethi = Rs. 2500
After allowing 5% of discount then S.P = M.P. – Discount%
= 2500 – \(\frac{5}{100}\) × 2500 = 2500 – 125 = Rs. 2375
Again 3% discount is allowed on Rs. 2375 then
S.P = 2375 – 3% of 2375
= 2375 – \(\frac{3}{100}\) × 2375 = 2375 – 71.25 = Rs. 2303.75
If 8% discount is allowed then S.P =

The S.P’s of both cases are not equal.
Discount on 5% + Discount on 3% = 125 + 71.25 = Rs. 196.25
Discount on 8% = Rs. 200
∴ Discounts are not equal which are obtained by Preethi.

Question 4.
What happens if cost price = selling price. Do we get any such situations in our daily life?
It is easy to find profit % or loss% in the above situations. But it will be more meaningful if we express them in percentages. Profit % is an example of increase percent of cost price and loss % is an example of decrease percent of cost price. (Page No. 106)
Answer:
If selling price is equal to cost price then either profit or loss will not be occurred.
In our daily life S.P. will not be equal to C.P. Then profit or loss will be occurred.
∴ Profit % = \(\frac{\text { Profit }}{\text { C.P. }}\) × 100;
Loss % = \(\frac{\text { Loss }}{\text { C.P. }}\) × 100.

Question 5.
A shop keeper sold two TV sets at Rs. 9,900 each. He sold one at a profit of 10% and the other at a loss of 10%. Oh the whole whether he gets profit or loss? If so what is its percentage? (Page No. 108)
Answer:
S.P of each T.V = Rs. 9,900
S.P of both T.Vs = 2 × 9,900 = Rs. 19,800
10% profit is allowed on first then C.P. =

10% loss is allowed on second then C.P.

C.P. of both T.V.’s = 9000 + 11000 = Rs. 20,000
Here C.P > S.P then loss will be occurred.
∴ Loss = C.P – S.P = 20000 – 19,800 = 200

Question 6.
What will happen if interest is compounded quarterly? How many conversion periods will be there? What about the quarter year rate – how much will it be of the annual rate? Discuss with your friends. (Page No. 115)
Answer:
Here C.I will be calculated for every 3 months. So, 4 time periods will be occurred in 1 year.
Rate of Interest (R) = \(\frac{R}{4}\) [∵ \(\frac{12}{3}\) = 4]

A = P\(\left[1+\frac{R}{400}\right]^{4}\)

AP State Syllabus AP Board 8th Class Biology Solutions Chapter 3 Story of Microorganisms 2 Textbook Questions and Answers.

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

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

Improve Your Learning

Question 1.
How do vaccines works in our body?
Answer:
When a vaccine is given which contains weak microorganisms our body learn to fight them by producing antibodies whenever danger comes. When the disease causing microorganisms enter in our body, the already present antibodies fight and eliminate them. And the disease is controlled. The weakened disease causing microorganisms which are injected into our bodies are called as vaccine.

Question 2.
What are the differences between Antibiotic and Vaccine?
Answer:

Antibiotic	Vaccine
An antibiotic is a compound or a substance that inhibits or kills the growth of bacteria.	Vaccine is a preparation that improves the immunity to a particular disease.
An antibiotic heals infection caused by small pox.	A vaccine prevents diseases like polio, bacteria.
Antibiotics are available in different forms like tablets, capsules, drops or ointments.	Vaccines can be given orally or through injection.
Antibiotics are taken after getting infected.	Vaccines are preventive method that is taken before getting infected.

Question 3.
Invention of pencillin protected the world from deaths during first world war, Explain.
Answer:

1. Pencillin was invented by Dr. Alexander Flemming.
2. He was an army doctor in First World War.
3. In the First World War many injured soliders died because of bacterial infection of wounds.
4. Pencillin killed many disease causing bacteria.
5. So the invention of pencillin protect the world from deaths during the first World War.

Question 4.
Take three bowls and mark as A,B,C. Pour lukewarm milk in bowl A, hot milk in bowl B, cold milk in bowl C. Add one tea spoon of curd or butter milk in three bowls and stir them slightly. Cover the bowls with lids. Keep the bowls undisturbed for five to six hours. In which bowl milk turned into curd ? Give your reasons.
Answer:
After six hours the milk in the bowl A converted into curd.
This conversion is happened by fermentation. Fermentaion is one kind of enzy-matic action in anaerobic respiration. Fermentation needs the help of microbes like yeast or some other bacteria. This process occurs at a particular temperature. Be-cause of enzymes are inactive at low and high temperatures. Hence the milk in bowl A converted into curd by the bacterium Lactobacillus.

Question 5.
Collect more information about scientists who invented and discovered other facts related to Microorganisms. How these discoveries helped mankind ? Make a chart presentation and paste it on your classroom wall magazine.
Answer:

Question 6.
Make an album of scientists and their discoveries related to Microorganisms.
Answer:

Question 7.
Visit the veterinary hospital and prepare a list of cattle diseases by asking questions, to the doctor.
Answer:

Disease	Animal
1) African Horse Sickness	Horses
2) Bovine Spongiform Encephalopathy	Cattle
3) Contagious Equine Metritis	Horses
4) Equine Infectious Anaemia	Horses
5) Anthrax	Cattle and other mammals
6) Brucellosis (Brucella abortus)	Cattle
7) Brucellosis (Brucella melitensis)	Sheep and Goats
8) Contagious agalactia	Sheep and Goats
9) Contagious bovine pleuro – pneumonia	Cattle
10) Dourine	Horses
11) European Bat Lyssavirus (FBLV)	Bats
12) Enzootic bovine leukosis	Cattle

Question 8.
What is pasteurisation? What is the use of it?
Answer:

1. Pasteurisation is a process which helps in the preservation of the milk.
2. It is discovered by “Louis Pasteur.” Hence it is called as pasteurisation.
3. In this process milk is heated up to 70° for 15 to 30 seconds and suddenly chilled and stored.
4. This prevents the growth of the microorganisms.

Question 9.
How do you appreciate Edward Jenner’s experiment?
Answer:

Edward Jenner was a man of the Enlightenment and believed in the intellectual and moral improvement of mankind.
Possessing that spirit, he predicted in 1801 that “the annihilation of small pox-the most dreadful scourge of the human race-will be the final result of this practice” of vaccination. And he was right. Since the Enlightenment, the core branches of science and medicine have generally developed rationally. As a result, the World Health Organization was able to declare in 1980 that smallpox had been eradicated worldwide. Only two laboratory samples emained, one in Russia and one in the United States.

Question 10.
Visit a nearby milk chilling centre. Observe the process and make a report on it.
Answer:
The Milk Collection Station is a specially designed, integrated unit, which combines the several functions of a milk collection centre. It measures the weight, fat content and gives the price of the milk brought in by the each producer. The equipment is particularly useful for the milk cooperatives / milk collection centres as it can also maintain a summary of milk supplied. This state of the art equipment operates both on battery and mains and is able to process and record 120-150 milk collection per hour. An Electronic Milk Weighing Unit, the Electronic Milk Tester and Data Processor Unit are main components of the system. The membership code of individual mem¬bers is entered automatically by member identity card / manually by an electronic key-board.

Question 11.
“Prevention is better than cure” comment.
Answer:
We heard about “prevention is better than cure” since our childhood – brushing of teeth twice to prevent tooth decay, washing of hands before eating to prevent stomach upset, do not eat uncovered road side food items, get vaccine against polio to free from disability, get rid of stagnate water to prevent malaria like that follow the life skills to avoid dangerous AIDS. It’s better to take care that a problem does not happen than to have to solve the problem afterwards. It’s easier to stop something bad from happening in the first place than to fix the damage after it has happened.

Question 12.
Raheem tells to his neighbours, “stagnation of’ sewage in our surroundings is harmful to our health. ” Do you support this? Why?
Answer:
Stagnation of sewage in our surroundings is harmful to our health in different ways. Sewage consist different wastes of organic matters. Microbes decompose all organic wastes. Disease transmitting carriers prefer to grow on decomposing organic matters. Hence sewage provides good shelter to mosquitoes, houseflies and other insects which transmit life threatening diseases like encephalitis, malaria, cholera, typhoid and other epidemics. Therefore sewage stagnation is more harmful to our health.

Question 13.
Jeevan said that “If there are no microorganisms earth will remain with wastes. ” Will you agree this statement? Why?
Answer:
Yes, I will agree this statement. Because of:

1. Microorganisms present in the soil, air and water act upon wastes around us.
2. They decomposes them.
3. They are converted into simple substances.
4. Thus microorganisms help us in cleaning the environment.
5. So if there are no microorganisms earth will remain with wastes.

Question 14.
Pranavi is suffering from serious illness. Doctor prescribed antibiotics for five days. After three days of usage she stopped taking antibiotics. Is it right or not, discuss.
Answer:
No, it is not right. Doctor prescribed anitbiotics for five days. Because the doctor knows that the correct days of the recovering of her illness. After three days of usage she stopped taking antibiotics. But her illness is not completely recovered. It is breaking out after some time. So it is not right.

Question 15.
What are the precautions taken to eradicate malaria?
Answer:

1. Malaria is caused by the pathogen piasmodium, is transmitted by female Anopheles mosquito.
   
2. Methods used to prevent malaria include medications, mosquito elimination and the prevention of bites.
3. Using of indoor mosquito repellents, residual sprays, taking care not to store water.
4. Providing awareness how to control mosquito population.

Question 16.
One medical store owner is giving antibiotics to his customer who is suffering from fever without doctor’s prescription? But the customer’s daughter Malathi is telling her father not to take antibiotics without doctor’s prescription. Whom do you support and why?
Answer:
We must use antibiotics prescribed by qualified doctor only. If you use antibiotics without consulting a qualified doctor it may harm us. Unnecessary use of antibiotics affects blood cells which fight infections. Sometimes they may kill useful bacteria too in our intestine and this increases the resistance towards antibiotics.

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

Question 1.
What diseases can be prevented if we control mosquitoes?
Answer:
Malaria, Dengue, Chickungunya, Japanese Encephalitis.

Question 2.
Which diseases can we prevented by vaccination?
Answer:
Tuberculosis, Chickenpox, Measles, Polio, Swineflu.

Question 3.
Name the diseases which are transmitted by contaminated water?
Answer:
Cholera, Typhoid

Question 4.
Can you name some diseases which are transmited by Air?
Answer:
Tuberculosis, Chickenpox, Measles, Polio, Swineflu.

8th Class Biology 3rd Lesson Story of Microorganisms 2 Activities

Activity – 1

Question 1.
Take some lukewarm milk in two small bowls. Add a few drops of butter milk or little curd in one of the bowls. In the second bowl do not add anything. Keep the two bowls in a warm place and observe the milk in the bowls after 5 to 6 hours.
a) What changes did you observe?
Answer:
In the first bowl milk changed into curd. There is no change in the second bowl.
b) What is the reason for this?
Answer:
We add curd or butter milk in the first bowl. Curd or buttermilk contain bacterium named lactobacillus. Lactobacillus converts the milk into curd.

Activity – 2

Question 2.
Take 100 grams of maida in a bowl, add one or two spoons of yeast powder, add some water and knead it to make dough. Keep the dough in a warm place. Observe the dough after 3 – 4 hours.
a) What changes do you observe in the dough ?
Answer:
We observe that the dough rises and increase its volume.
b) What might be the reason ? Discuss with your friends and write about it.
Answer:
When yeast is added to the maida dough, the dough rises. This is due to the produc¬tion of carbondioxide gas during the process of fermentation. Bubbles of the gas fill the dough, increase its volume and make it spongy in nature.

Activity – 3

Question 3.
Commercial use of microorganisms.
Take some water in two separate beakers. Add 5 to 10 spoons of sugar to each beaker, then add 2 to 3 spoons of yeast to one of the bowls only. Close both of the bowls with lids and keep them in a warmplace. After 3 to 4 hours remove the lids and smell the contents.
a) What differences did you observe between the two bowls?
Answer:
We feel a new variety of smell from one of the bowls. This is the characteristic smell of alcohol. There is no smell from another bowl.
b) What will be the reason for the odour in yeast mixed bowl?
Answer:
Sugars are converted into alcohol by yeast. This process of conversion of sugars into alcohol is known as fermentation.

Activity – 4

Question 4.
Visit nearby PHC and collect information about vaccination given to 0-15 years chil-dren. Meet a doctor or a health worker and ask what types of vaccines are there ? Which disease can be prevented ? When it should be taken? List them out.
Answer:

Activity – 5

Question 5.
Take two pots or dig two pits in the corner of the garden at home or at your school ground. Fill them up to half with loose soil. Put some biological wastes like fallen leaves, vegetable wastes, waste papers, etc., in one of them. Fill the second one with plastic wastes, polythene bags and with some empty glass bottles.
Answer:
Now cover both the pits with soil and sprinkle water twice a day up to three weeks and observe the changes in both the pits and record.
After three weeks the pit which consists organic wastes decomposed into inorganic matter. But the pit which is filled with polythene bags, plastics and glass bottles is remain same no change is observed. Because of plastics and polythene materials are non biodegradables.

Activity – 6

Question 6.
Meet a doctor of your locality and ask him about the different types of diseases, caused by different microorganisms. Note them down. (OR)
Read the following table and answer the following questions.


Questions:
a) Name the viral diseases that can be prevented by controlling mosquito population.
Answer:
Dengue, Chikungunya, Japanese encephalitis.

b) Which bacterial disease / diseases cannot be controlled by vaccination (acc.to above table) ?
Answer:
Cholera, Typhoid.

c) What would you do to control mosquito population ?
Answer:
Use mosquito repellents, control breeding of mosquitoes by not allowing water stag¬nation in our surroundings.

d) Name the viral disease that spreads through water.
Answer:
Polio.

AP State Syllabus 8th Class Maths Solutions 9th Lesson Area of Plane Figures InText Questions

AP State Syllabus AP Board 8th Class Maths Solutions Chapter 9 Area of Plane Figures InText Questions and Answers.

8th Class Maths 9th Lesson Area of Plane Figures InText Questions and Answers

Do this

Question 1.
Find the area of the following figures:     [Page No. 200]
i)

Answer:
Area of a parallelogram = b × h = 7 × 4 = 28 sq.cm.

ii)

Answer:
Area of a triangle = \(\frac{1}{2}\) bh = \(\frac{1}{2}\) × 7 × 4
= 14 sq.cm.

iii)

Answer:
Area of a triangle = \(\frac{1}{2}\) bh = \(\frac{1}{2}\) × 5 × 4
= 10 sq.cm.

iv)

Answer:
Area of rhombus = \(\frac{1}{2}\) d₁d₂
= \(\frac{1}{2}\) × (4+4) × (3+3)
[∴ d₁ = 4 + 4 = 8, d₂ = 3 + 3 = 6]
= \(\frac{1}{2}\) × 8 × 6
= 24 cm²

v)

Answer:
Area of a rectangle = l × b
= 20 × 14 = 280 sq.cm

vi)

Answer:
Area of a square = s²
= s × s
= 5 × 5 = 25 cm²

Question 2.
The measurements of some plane figures are given in the table below. However, they are incomplete. Find the missing information.     [Page No. 200]
Answer:

Question 3.
Find the area of the following trapezium.      [Page No. 204]
fig (i)

Answer:
Area of a trapezium

fig (ii)

Answer:
Area of a trapezium

Question 4.
Area of a trapezium is 16 cm². Length of one parallel side is 5 cm and distance between two parallel sides is 4 cm. Find the length of the other parallel side. Try to draw this trapezium on a graph paper and check the area.
[Page No. 204]
Answer:
Given that
Area of a trapezium = 16 sq.cm
Length of one of the parallel sides is a = 5 cm; h = 4 cm
Length of 2nd parallel side (b) = ?
A = \(\frac{1}{2}\)h(a + b)

Graph Sheet:

Area of parallelogram ABCD = 12 sq.cm + (S + P) + (Q + R) + (W + T) + (V + U)
= 12 + 1 + 1 + 1 + 1
= 12 + 4
= 16 sq.cm

Question 5.
ABCD is a parallelogram whose area is 100 sq.cm. P is any point insile the parallelogram (see fig.) find tie area of △APB + △CPD.       [Page No. 204]

Answer:
Area of parallelogram ABCD = 100 sq.cm
From the given figure,
ar (△APB) + ar (△CPD) = ar (△PD) + ar (△BPC)

Question 6.
The following details are noted in meters in the field book of a surveyor. Find the area of the fields.     [Page No. 213]
i)

Answer:

From the above figure
i) A, B, C, D, E are the vertices of pentagonal field,
ii) AD is the diagonal.
iii) Now the area of the field = Areas of 4 triangles and a trapezium.
PQ = AQ – AP = 50 – 30 = 20
QD = AD – AQ = 140 – 50 = 90
RD = AD – AR = 140 – 80 = 60
Area of △APB:

Area of trapezium PBCQ:

Area of △QCD:

Area of △DER:

Area of △ERA:

∴ Area of the field = ar △APB + ar trapezium PBCQ + ar △QCD + ar △DER + ar △ERA
= 450 + 800 + 2250 + 1500 + 2000 = 7000 sq. units
ii)

Answer:

From the above figure
i) A, B, C, D, E are the vertices of a pentagonal field.
ii) AC is the diagonal.
iii) The area of a field is equal to areas of 4 triangles and a trapezium.
QC = AC – AQ = 160 – 90 = 70
RC = AC – AR = 160 – 130 = 30
PR = AR – AP = 130 – 60 = 70
Area of △AQB:

Area of △QBC :

Area of △DRC :

Area of trapezium EPRD:

Area of △EPA :

∴ Area of the field = ar △AQB + ar △QBC + ar △DRC + ar trapezium EPRD + ar △EPA
= 2700 + 2100 + 450 + 2450 + 1200 = 8900 sq. units

Try these

Question 1.
We know that parallelogram is also a quadrilateral. Let us split such a quadrilateral into two triangles. Find their areas and subsequently that of the parallelogram. Does this process in turn with the formula that you already know?   [Page No. 209]

Answer:
Area of a parallelogram ABCD

Area of parallelogram ABCD
= base x height
= bh sq. units
(OR)

Area of parallelogram ABCD
= ar △ABC + ar △ACD
= \(\frac{1}{2}\) BC × h₁ + \(\frac{1}{2}\) AD × h₂
= \(\frac{1}{2}\) bh + \(\frac{1}{2}\) bh [∵ h₁ = h₂]
= bh sq. units.
∴ This process in turn with already known formula.

Question 2.
Find the area of following quadrilaterals.      [Page No. 213]
i)

Answer:
d = 6 cm, h₁ = 3 cm, h₂ = 5 cm
Area of a quadrilateral
= \(\frac{1}{2}\)d(h₁ + h₂)
= \(\frac{1}{2}\) × 6 (3 + 5) = 3(8) = 24 cm²

ii)

Answer:
d₁ = 7 cm; d₂ = 6 cm
Area of a rhombus A = \(\frac{1}{2}\) d₁d₂
= \(\frac{1}{2}\) × 7 × 6
= 7 × 3 = 21 cm²

iii)

Answer:
Area of a parallelogram (A) = bh
(∵ The given fig. is a parallelogram in which two opposite sides are parallel)
Area of a parallelogram = 2 ar AADC
= 2 × \(\frac{1}{2}\) × 8 × 2 = 16 Sq. cm.
[∵ Area of a parallelogram = ar △ADC + ar △ABC. But ar △ABC = ar △ADC]

Question 3.
i) Divide the following polygon into parts (triangles and trapezium) to find out its area.     [Page No. 214]

Answer:
FI is a diagonal of polygon EFGHI.
If perpendiculars GA, HB are drawn on the diagonal FI, then the given figure pentagon is divided into 4 parts.
∴ Area of a pentagon EFGHI = ar △AFG + ar AGHB + ar △BHI + ar △EFI.

NQ is a diagonal of polygon MNOPQR. Here the polygon is divided into two parts.
∴ Area of a hexagon MNOPQR = ar NOPQ + ar MNQR.

ii) Polygon ABCDE is divided into parts as shown in the figure. Find the area.     [Page No. 215].

If AD = 8 cm, AH = 6 cm, AF = 3 cm and perpendiculars BF = 2 cm, GH = 3 cm and EG = 2.5 cm.
Answer:
Area of polygon ABCDE = ar △AFB + ar FBCH + ar △HCD + ar △AED

So, the area of polygon ABCDE = 3 + 7.5 + 3 + 10 = 23.5 sq.cm

iii) Find the area of polygon MNOPQR if MP = 9 cm, MD = 7 cm, MC = 6 cm, MB = 4 cm, MA = 2 cm.   [Page No. 215].

NA, OD, QC and RB are perpendiculars to diagonal MP.
Answer:
Area of MNOPQR
= ar △MAN + ar ADON + ar △DOP + ar △CQP + ar BCQR + ar △MBR
Hence CP = MP – MC = 9 – 6 = 3 cm
BC = MC – MB = 6 – 4 = 2 cm
AB = MB – MA = 4 – 2 = 2 cm
DP = MP – MD = 9 – 7 = 2 cm
AD = MD – MA = 7 – 2 = 5 cm

= 2.5 + (2.5 × 5.5) + 3 + 3 + 4.5 + (2 × 2.5)
= 2.5 + 13.75 + 3 + 3 + 4.5 + 5
= 31.75 sq.cms

Think, discuss and write

Question 1.
A parallelogram is divided into two congruent triangles by drawing a diagonal across it. Can we divide a trapezium into two congruent triangles?    [Page No. 213]
Answer:

No, we cannot divide a trapezium into two congruent triangles.
∵ From the adjacent figure,
△ABC ≆ △ADC

AP State Syllabus AP Board 8th Class Maths Solutions Chapter 15 Playing with Numbers Ex 15.6 Textbook Questions and Answers.

AP State Syllabus 8th Class Maths Solutions 15th Lesson Playing with Numbers Exercise 15.6

Question 1.
Find the sum of integers which are divisible by 5 from 1 to 100.
Solution:
Numbers which are divisible by 5 from 1 to 100 are 5, 10, 15, …………………95, 100.
∴ Sum of the above numbers = 5+10 + ……………..+ 95 + 100
= 5[1 + 2 + ………………….+ 20]
= 5 [ \(\frac{20 \times(20+1)}{2}\) ]
= \(\frac{5 \times 20 \times 21}{2}\) [∵ Sum of ‘n’ natural numbers = \(\frac{n(n+1)}{2}\) & n = 20 ]
= 1050

Question 2.
Find the sum of integers which are divisible by 2 from 11 to 50.
Solution:
. Numbers which are divisible by 2 from 11 to 50 are 12, 14,48, 50.
Sum of the numbers = 12 + 14 + ……….. + 48 + 50 ‘
= (2 + 4 + ……….. + 50) – (2 + 4 + ……….. + 10)
= 2(1 + 2 +……….. + 25) – 2 (1 + 2 + ……….. + 5)

= 25 × 26 – 5 × 6
= 650 – 30
= 620

Question 3.
Find the sum of integers which are divisible by 2 and 3 from 1 to 50.
Solution:
Numbers which are divisible by 2 and 3 i.-e., which are divisible by 6 from 1 to 50 are 6,12 …………….48.
Sum of the numbers = 6 + 12 + ……..+ 48
= 6(1 + 2 +……… + 8)
= 6 \(\left[\frac{8(8+1)}{2}\right]\)
= 3 × 8 × 9 = 216

Question 4.
(n³ – n) is divisible by 3. Explain the reason.
Solution:

∴ If n = 4, (n³ – n) is divisible by 3.
∴ (n³ – n) is divisible by all the values of n.
Method 2:
n³ – n = n(n² – 1)
= n(n + 1)(n – 1)
∴ (n³ – n) is divisible by ‘3’ for all the values of n.
[∵ (n – 1), n, (n + 1) are three consecutive odd numbers]

Question 5.
Sum of ‘n’ odd number of consecutive numbers is divisible by ‘n’. Explain the reason.
Solution:
Sum of n’ consecutive odd numbers = n²
Since n is a factor of n², It Is divisible by ‘n’.

Question 6.
Is 1¹¹ + 2¹¹ + 3¹¹ + 4¹¹ divisible by 5? Explain.
Solution:
Sum of units digit of number 1¹¹ + 2¹¹ + 3¹¹ + 4¹¹
= 1 + 8 + 7 + 4
= 20 → \(\frac{20}{5}\)(R = 0)
∴ 1¹¹ + 2¹¹ + 3¹¹ + 4¹¹ is divisible by 5.

Question 7.

Find the number of rectangles of the given figure?
Solution:

∴ No.of rectangles in the given figure = 1 + 2 + 3 + 4 + 5 + 6 = 21

Question 8.
Rahul’s father wants to deposit sorne amount of money every year on the day of Rahul’s birthday. On his 1st birth day Rs.100, on his 2nd birth day Rs.300, on his 3 birth day Rs.600, on his 4th birthday Rs. 1000 and so on. What is the amount deposited by his father on Rahul’s 15th birthday.
Solution:

Rahul’s father deposits on every year 200, 300, 400 more than before year.
Then he deposits ₹ 10,500 on 14th birthday.
∴ The amount deposits on 15th birthday
= 10,500 + 1,500
= ₹ 12,000/-

Question 9.
Find the sum of integers from 1 to 100 which are divisible by 2 or 5.
Solution:
Sum of the numbers which are divisible by 2 from 1 to 100
= 2 + 4 + ……….. + 100
= 2(1 + 2 + ………… +50)
= 2 × \(\frac{50 \times(50+1)}{2} \)
= 50 × 51 = 2550
Sum of the numbers which are dMsible by 5froin I to 100
= 5 + 10 + ……….. + 100
= 5(1 + 2 +……….. +20)
= 5 × \(\frac{20 \times(20+1)}{2}\)
=5 × 10 × 21
=1050

Sum of the numbers which are.divisible by both 2 and 5 = 2550 + 1050 =3600
∴ Sum ol the numbers which are divisible by 2 or 5 from 1 to 100
= 10 + 20 + ………..+ 100 ( L.C.M of 2, 5 is 10)
=10(1 + 2 + ………..+ 10)
= 10 × \(\frac{10 \times(10+1)}{2}\)
= 5 × 10 × 11 .
= 550
∴ The sum of required numbers 3600—550 3050

Question 10.
Find the sum of integers from 11 to 1000 which are divisible by 3.
Solution:
Sum ol the numbers which are divisible by 3 from lito 1000
= 12 + 15+ ……….. +099
= 3(4 + 5 + ……….. +333)
= 3(1 + 2 + ……….. + 333) – 3(1 + 2+3)

= 999 × 167 – 9 × 2
= 166833 – 18
= 166815