Class 8

AP State Syllabus AP Board 8th Class English Textbook Solutions Chapter 6B Be Thankful Textbook Questions and Answers.

AP State Syllabus 8th Class English Solutions Chapter 6B Be Thankful

8th Class English Chapter 6B Be Thankful Textbook Questions and Answers

Comprehension

Answer the following questions.

Question 1.
The poet depicts different situations/aspects of life where we need to be thankful. What are they?
Answer:
We need to be thankful to the following situations/aspects of life:

1. When we don’t know something;
2. When we face difficult times;
3. When we have certain limitations;
4. When we face new challenges;
5. When we make mistakes;
6. When we are tired and weary;
7. When we suffer setbacks and
8. When we face troubles.

Question 2.
Do you agree to the poet’s idea? Yes/No? Give reasons.
Answer:
Yes, I agree to the poet’s ideas. We need to be thankful that we don’t already have everything we desire. If we get everything we desire, there will be nothing to look forward to do. If we don’t know something, we will try to learn about it. We grow in the difficult times. We try to find out a solution to get rid of our difficulties. When we have limitations, we try to overcome them. In the process of facing the new challenges, we will build our strength and character. Our mistakes will teach us valuable lessons. When we suffer setbacks it will bring out our innate powers. All these things make us perfect ones.

Question 3.
How do the difficulties help us grow? When will the troubles become blessings?
Answer:
The difficulties help us grow. When one faces difficulties, one tries to get rid of them. It makes the person to think in the right way and find the right solution. Thus he is able to get out of his difficulties. When one finds a way to be thankful for one’s troubles, the troubles become blessings.

Be Thankful Summary in English

We need to be thankful that we don’t already have everything we desire. There would be nothing to look forward to do if we get everything we desire. We need to be thankful when we don’t know something for it gives us the opportunity to learn. We need to be grateful when we face the difficult times as we grow during those times. We need to be thankful for our limitations as they give us opportunities for improvement. We need to be grateful for each new challenge as it will build our strength and character. We need to be thankful for our mistakes as they will teach us valuable lessons. We need to be thankful when we are tired and weary as it means we have made a difference. It is easy for all of us to be thankful for the good things. But we need to be thankful even for the setbacks to get a life of rich fulfillment. Gratitude can change a negative into a positive. We need to find a way to be thankful for our troubles as they can become our blessings.

Be Thankful Glossary

desire (n): a strong wish to have or do something

character (n): all the qualities and features that make a person, groups of people, and places different from others

weary (adj): very tired

AP State Syllabus AP Board 8th Class English Textbook Solutions Chapter 6A Dr. Dwarakanath Kotnis Textbook Questions and Answers.

AP State Syllabus 8th Class English Solutions Chapter 6A Dr. Dwarakanath Kotnis

8th Class English Chapter 6A Dr. Dwarakanath Kotnis Textbook Questions and Answers

Read the newspaper headline given below and answer the questions that follow.

International Nurses’ Day : President gives away Florence Nightingale Awards

President Pratibha Patil giving away Florence Nightingale Award to S. Hoikholhing on 12th May 2012.

Question 1.
Why are the nurses given awards on the name of Florence Nightingale?
Answer:
Florence Nightingale Awards are annually given for excellence in nursing. The main aim of giving these awards to the nurses is to recognize professional nurses for their contributions to direct patient care.

Question 2.
Do you know the name of any Indian who may have rendered any significant services in another country and is still remembered and honoured by the people there?
Answer:
Yes, I know the name of an Indian who rendered his significant services in another country and is still remembered and honoured by the people there. He is none other than Dr. Dwarakanath Shantaram Kotnis. He was one of the five Indian physicians dispatched to China to provide medical assistance during the second Sino-Japanese War. No other Indians can claim the kind of adulation and respect Dr. Kotnis enjoys in China.

Comprehension

Answer the following questions.

Question 1.
Why was Dr. Kotnis sent to China?
Answer:
In 1937, the communist General Zhu De requested Jawaharlal Nehru to send Indian physicians to China during the Second Sino-Japanese War to help the soldiers. The President of the Indian National Congress, Netaji Subhash Chandra Bose accepted the request and made arrangements to send a team of volunteer doctors. A medical team of five doctors M. Atal, M.Cholkar, D. Kotnis, B.K. Basu and D. Mukeiji was sent as the part of Indian Medical Mission Team in September 1938. Thus Dr. Kotnis was sent to China to help the Chinese soldiers.

Question 2.
What was Dr. Kotnis’ contribution to the Dr. Bethune International Peace Hospital in China?
Answer:
Dr. Kotnis once served as Dr. Bethune International Peace Hospital’s doctor. He took over the post of the first President of the Bethune International Peace Hospital after Dr. Norman Bethune passed away. He worked as a lecturer earlier for sometime in the military area at the Dr. Bethune Hygiene School.

Question 3.
Why did Dr. Kotnis opt to stay back in China?
Answer:
After the Second Sino-Japanese War, all other doctors except Dr. Kotnis, returned to India. However, Dr. Kotnis decided to serve at the military base. So he opted to stay back in China.

Question 4.
How did the Chinese show their gratitude towards Dr. Kotnis?
Answer:
In order to cherish the memory of Dr. Kotnis, the Chinese government built a memorial hall for him in Shijiazhuang city, Hebei Province in 1976. Along with the Candian Dr. Norman Bethune, he continues to be revered by the Chinese people. In April 2005, both their graves were covered completely in flowers donated by the Chinese people during the Qingming Festival. A small museum there has a hand book which contains words that Kotnis wrote in his “Passage from India to China,” some of the instruments that the surgeon^ used at their time and many photogrpahs of doctors. China has honoured him with stamp in 1982.

Question 5.
Why was Mrs. Kotnis a regular invitee at the Indian Embassy functions in China?
Answer:
Mrs. Kotnis had been an honoured guest at many high-level diplomatic functions between China and India. She was a regular invitee at the Indian Embassy fuctions in China, because
the Chinese wanted to have good relationship with India. Not only that, to respect Dr. Kotnis’ selfless service to the Chinese, she was invited at the Indian Embassy functions in China.

Question 6.
What sort of person, do you think, was Dr. Kotnis? What are your impressions about him?
Answer:
Dr. Kotnis dedicated his entire life working as a battlefront doctor in China and rendered his selfless service to the injured Chinese soldiers during the Second Sino-Japanese War. Dr. Kotnis’ contribution towards humanity will be remembered forever. No single Indian has been more revered by ordinary Chinese than Dr. Kotnis. He was not only a hero but also a loved brother, husband and an adventurous young man.

II. Read the passage about Dr. Kotnis again and fill in the form given below.

1. Name:
2. Year of birth:
3. Place of birth:
4. Occupation:
5. Nationality:
6. Wife’s name:
7. Places of work and the positions held:
8. Honours given by China and India:
9. Date of death:
Answer:
1. Name Dwarakanath Kotnis
2. Year of birth 1910 (October 10,1910)
3. Place of birth Sholapur, Maharashtra
4. Occupation Doctor
5. Nationality Indian
6. Wife’s name Guo Qinglan
7. Places of work and the positions held:
(a) Yan’an → doctor
(b) Eighth Route Army General Hospital, North China → physician-in-charge
(c) Dr. Bethune Hygiene School → lecturer
(d) The Bethune International Peace Hospital → president
8. Honours given by China and India:
(a) The Chinese government built a memorial hall for him in Shijiazhuang city, Hebei Province in 1976.
(b) In April 2005, his grave was covered completely in flowers donated by the Chinese people during the Qingming Festival.
(c) A small museum there has a hand book which contains words that Kotnis wrote in his “Passage from India to China”.
(d) Both China and India honoured him with stamps in 1982 and 1993 respectively.
9. Date of death: 9th December, 1942.

Vocabulary

I. Here are some of the words that are related to the word ‘doctor’. In how many ways can you classify the following words?

Mapping these meanings through words is called semantic mapping. A set of words related in meaning are said to belong to the same semantic field.
e.g. : bus, driver, conductor, ticket, etc.
Write four words that belong to and that you can associate with the following words.
1. space                 (a)            (b)             (c)             (d)
2. business            (a)             (b)            (c)             (d)
3. occupation        (a)             (b)            (c)             (d)
4. travel                 (a)             (b)            (c)             (d)
Answer:
1. space                 (a) space-shuttle     (b) space travel     (c) space station      (d) spaceship
2. business            (a) selling                 (b) buying             (c) exports               (d) imports
3. occupation        (a) teacher               (b) driver               (c) collector             (d) conductor
4. travel                 (a) road                    (b) rail                   (c) sea travel            (d) air travel

II. Read the sentence given below.
Dr. Kotnis lost his heart to a Chinese woman.
What does the expression ‘lose heart’ in the above sentence mean?
Lost his heart means fell in love.
Here is one more expression using the word heart.
‘Eat your heart out’. (Suffer from envy or jealousy)
e.g.: I am going to New York next week. Eat your heart out!
e.g.: When he hears about your promotion he will eat his heart out.

III. Match the following.
1. have a heart         ( )      (a) sadness
2. broken heart        ( )      (b) no feelings
3. heavy heart          ( )      (c) a very deep thank you
4. take to heart        ( )      (d) be merciful
5. a heart of stone   ( )      (e) lost love
6. thanks from the bottom of my heart ( ) (f) take seriously
Answer:
ANSWERS
1 – d,
2 – e,
3 – a,
4 – f,
5 – b,
6 – c

Grammar

Coordination is a grammatical process by which two or more words phrases or clauses of the same rank are conjoined.
A conjunction that joins parts of a sentence (words, phrases or clauses) that are grammatically equal or similar in importance and structure is called a Coordinating Conjunction, e.g: and, but, or, nor, for, yet, so.
Coordinating Conjunctions: and, but, or, yet, so, neither… nor, either…. or, not only
but also, both, etc.
Subordinate Conjunctions: when, before, after, since, while, as, till, until, whenever, as long as, as soon as, no sooner….than, then, scarcely, hardly,…. when, wherever, because, in order that, so….that, if, though, even though, whereas, as if, whether …. or, etc.

Compound Sentence and Complex Sentence

Observe the following sentences.
1. Dr. Kotnis was a doctor and Guo, a nurse.
2. I could not stop laughing when he told jokes.

• What are the main clauses in each sentence?
• How many subordinate clauses are there in sentences 1 and 2?

Dr. Kotnis was a doctor and Guo, a nurse, (two main clauses)
I could not stop laughing when he told jokes, (one main clause and one subordinate clause) I could not stop laughing’ is a main clause, ‘when he told jokes’ is a subordinate clause.

• A sentence which consists of two or more main clauses combined with coordinate conjuctions is called a Compound Sentence.
• A sentence which consists of one main clause and one or more subordinate clauses combined with subordinate conjuctions is called a Complex Sentence.

Read the following sentences. Identify the clauses and say whether they are main clauses or subordinate clauses.
1. John suffers from Asthma but attends school regularly.
2. We like songs but they like games.
3. Japan attacked China in 1937 and wounded many soldiers.
4. If the rain stops, we will go out.
5. She was unhappy or she was upset.
6. The shops were closed because there was a strike.
Answer:
1. John suffers from Asthama but attends school regularly.
Main clause – John suffers from Asthama
Main clause – (he) attends school regularly.

2. We like songs but they like games.
Main clause – We like songs
Main clause – they like games.

3. Japan attacked China in 1937 and wounded many soldiers.
Main clause – Japan attacked China in 1937.
Main clause – (Japan) wounded many soldiers.

4. If the rain stops, we will go out.
Main clause – We will go out.
Subordinate clause – If the rain stops

5. She was unhappy or she was upset.
Main clause – She was unhappy
Main clause – She was upset.

6. The shops were closed because there was a strike.
Main clause – The shops were closed.
Subordinate clause – because there was a strike.

Writing

Developing Headlines.
When writing a news report for a newspaper, or your school News Board, the headline is the first and foremost impression you make on your reader. Therefore, writing a headline is a critical and creative art. „
Most of the people read only the headlines while reading a newspaper, to get the gist of the news.

• Headlines often contain a noun phrase with no verb.
• Headlines may have noun strings (several nouns put together).
• Various changes are made in the headlines.
• The simple tense form is used instead of the continuous or perfect form.
• The infinite form refers to the future.
• The auxiliary verb is dropped in the passive form.
• Articles are dropped; full-stops are not placed after headlines.
• Headlines may contain initials and abbreviations, e.g : Prime Minister’s advice

e.g : Man snatches woman’s chain
e.g : Andhra Pradesh State Board Examination Results Declared
e.g : Hyderabad celebrates kite festival
e.g : Chief Minister to inaugurate Craft Bazars
e.g : Passengers injured seriously in Nellore train accident
e.g : India to host SAARC meet in UP

I. Now write a headline for each of the following news reports. Remember to pick out only the main idea or words from the sentence.
(a) Hyderabad: With an alarming rise in cases of missing people, especially women and children, since 2009, the Andhra Pradesh Police have stepped up measures to trace them in co-ordination with various agencies and police forces.
Answer:
Andhra Pradesh police have stepped up measures to trace missing people

(b) The full moon that rises on this Friday night, August 31,2012, will be a Blue Moon. That’s what it has been dubbed as in modern folklore of the west. But will it actually be blue?
Answer:
A Blue Moon to rise on Friday night, August 31, 2012

(c) “If you look at the last three months, I am really practising well. ! am looking forward to playing my first game after a year.”
Answer:
I am to play my first game after a year

(d) Next time your cell phone runs out of battery, you can charge it by just holding it in your hands as the scientist claims to have developed a new technology that turns body heat into electricity.
Answer:
A new technology that runs body heat into electricity developed

II. Look at the picture where students are serving in an old age home.

Discussion Points

1. Do old people go to old age homes on their own or are they forced to go there?
2. What are the conditions which make people leave their own homes and go to an old age home?
3. In what way are the conditions at an old age home different from those at home?
4. Are there any ways to prevent the old people from going to old age homes?
   Note : Answers for the 4 discussion points given above are given in Q. III.

III. Now write an article based on the following hints.

• What are old age homes?
• Why do old people go there?
• Facilities at the old age homes
• Compare facilities at home and old age homes

Answer:
The old age homes are intended for senior citizens. Nowadays, most of the old people prefer to live in old age homes. Many factors have contributed to the alienation of the elders. Migration of young couples from the rural areas to the cities in search of better employment opportunities to fend for themselves. Youngsters are sometimes unfair to their parents. They don’t show the old ones any love or affection. Sometimes the old people are not given enough food to eat. The young people don’t provide proper medical facilities for the old people. The young people don’t care for them. Parents take a lot of pain to grow their children and sacrifice a plenty of their happiness: Our culture has it, that it is duty of the child to look after his parents. Unfortunately, it doesn’t happen in our present society. Everyone is in a mad race of earning money. And in the process they don’t take time off to look after their parents. We don’t find good relationships and human values in our present society. Aged parents are like children. They are sensible. Nowadays, India is intensely influenced by the western world where parents live alone or stay at old age homes. The old people don’t go to old age homes on their own. They are forced to go there.
In the old age homes trained staff can assist the old people. They can be kept clean and fed well. Proper medical care is provided. Old age homes have special medical facilities for senior citizens such as mobile health care systems, ambulances, nurses and provision of well-balanced meals. Apart from food, shelter and medical amenities, the entertainment and library facilities are also available for them. These homes create a family like atmosphere among the residents. Senior citizens experience a sense of security and friendship when they share their joys and sorrows with one another. Here, they live peacefully. Old age homes provide them the much needed comfort, solace and companionship. We can prevent the old people from going to old age homes by showing them love and affection. The youngsters should take care of them. They should provide proper medical facilities for them. They should allow their parents to move and talk freely in their homes.

Listening

Listen to your teacher. She/He will read out an announcement made by the headmaster of a Govt. High School.

An Announcement in a School

Dear students,
I am to inform you that we are going to start an ‘Enrolment Drive Programme’ next week. We will go to the nearby slums in our locality for 3 days and see if there are any children who are not studying in any school. There will be 10 teams each consisting of 6 students. I want all the students and teachers of classes VIII and IX to join this mission. Mr. Rajkumar and Ms. Christina will be joining us in our mission. They will help us in all the aspects related to the programme. Children, now those who volunteer to take the lead in teams should meet their class teachers after the lunch hour.
Now, answer the following questions.
1. What is the announcement about?
Answer:
The announcement is about launching of ’Enrolment Drive Programme.’

2. Who are the special guests joining their mission?
Answer:
Mr. Rajkumar and Ms. Christina are the special guests joining their mission.

3. What are the students asked to do in the programme?
Answer:
The students are asked to go to the nearby slums in their locality for 3 days and see if there are any children who are not studying in any school.

4. Why does the headmaster call it a mission?
Answer:
The headmaster calls it a mission as he thinks that the ‘Enrolment Drive Programme’ is a very important programme.

Oral Activity

If you get an opportunity to propose a ‘Vote of Thanks’ after completing the Enrolment Drive Programme. How would you do it?
Prepare ‘Vote of Thanks’ to thank Mr. Rajkumar, Ms. Christina, and all other participants.
Clues :

• Introduction of the programme
• About the participants and the service they offered during the programme.
• Their role in making the Programme a great success.
• Thanking each and everyone referring to their role in the programme.
• Requesting the extension of their service in future.

Answer:
Good evening to all of you. I am proud and lucky to have the opportunity of proposing a ‘Vote of Thanks’ to thank all the participants. As you are all aware that our ‘Enrolment Drive Programme’ has come to an end and it is a great success for all of us recognizing the students who are outside the school and joining them in the school. At first I would like to thank our special guests Mr. Rajkumar and Ms. Christina on behalf of our school and on my behalf for sparing some of their valuable time for us. We are very much thankful to you sir and madam for the service offered by you during the programme and your valuable suggestions. We are hopeful that we will get your extended cooperation and help in the future. Once again I wish to express our sincere thanks to you sir and madam for your role in making this programme a grand success. Now, I would like to thank each and everyone who participate in this programme and make it a grand success. I would like to request all of you to extend your priceless services
in the future.

Dr. Dwarakanath Kotnis Summary in English

Dr. Dwarakanath Kotnis was born in a lower middle class family on October 10, 1910 in Sholapur, Maharashtra. Coming from a family of doctors, Dr. Kotnis aspired to become a doctor.

After completing his graduation in medicine, he went on to pursue his post-graduation internship. He started his medical expedition in Vietnam, and then, moved on to Singapore and Brunei. The communist General Zhu De requested Jawaharlal Nehru in 1937 to send Indian physicians to China to help the war victims. Dr. Kotnis was one of the five doctors who were sent to China as the part of Indian Medical Mission Team. Though the other doctors returned to India after the war, Dr. Kotnis decided to stay back and serve at the military base. He started his work in Yan’an and then worked in the surgical department of the Eighth Route Army General Hospital as the physician-in-charge. He fell in love with a Chinese nurse, Guo Qinglan and married her in November, 1941. They had a son on August 23, 1942 and he was named Yin Hua. He worked as a lecturer for sometime at the Dr. Bethune Hygiene School. Later he took over the post of the first President of the Bethune International Peace Hospital. He did operations for 72 hours nonstop without any sleep during the long-drawn out battle against Japan. He played a major role in controlling a virulent strain of plague that hit Chinese soldiers. He died of epilepsy on December 9, 1942 at the age 32, and was buried in the Heroes Courtyard, Nanquan Village.

The Chinese government built a memorial hall for him in Shijiazhuang city, Hebei Province in 1976. His grave was covered completely in flowers donated by the Chinese people during the Qingming festival. Both China and India honoured him with stamps in 1982 and 1983 respectively. Later, Kotnis, family visited Kotnis’ grave and Dr. Bethune International Peace Hospital.

After Dr. Kotnis’ death, their son Yin Hua also passed away when he was just 25. Despite the two premature deaths, Mrs. Kotnis maintained her links with the Kotnis family. Mrs. Kotnis had been an honoured guest at many high-level diplomatic functions between China and India. She was a regular invitee at the Indian Embassy functions in China. Dr. Kotnis become famous in his hometown with the publication of “One Who Never Returned” written by Khwaja Abbas Ahmed and the screening of the movie “Dr. Kotnis Ki Amar Kahani,” directed by V. Shantaram. No other Indians can claim the kind of adulation and respect Dr. Dwarakanath Kotnis enjoys in China. Dr. Kotnis’ contribution towards humanity will be remembered for ever.

Dr. Dwarakanath Kotnis Glossary

adulation (n): admiration; praise

virulent (adj): dangerous

shy away (phr.v): avoid something that you dislike

epilepsy (n): a disease of the nervous system that causes a person to fall unconscious

revered (v): respected or admired deeply

commemorate (v): keep a great person, event etc. in people’s memories

vivacious (adj): cheerful

venerated (v): respected

septuagenarian (n): a person who crossed 70 years

memorabilia (n): objects that are collected in memory of persons and events

render (v): to give somebody something

vivacious (adj): having a lively, attractive personality

pursue (v): to try to achieve something over a period of time

internship (n): a job that an advanced student of medicine, whose training is nearly finished, does in a hospital to get further practical experience

put aside (phr.v): to ignore or forget something, usually a feeling or difference of opinion.

expedition (n) : an organized journey with a particular purpose

lose heart (idiom): to fall in love with somebody

passed away (phr.v): died

fortnight (n): two weeks

soulmate (n): an intimate associate or companion ; someone with whom you have a special relationship and whom you know and love very much

cherish (v): to love somebody/something very much and want to protect them or it

AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 10 Reflection of Light at Plane Surfaces

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

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces 1 Mark Important Questions and Answers

Question 1.
What is reflection?
Answer:
The light rays falling on a surface are returned into the original medium. This phenomenon is called reflection.

Question 2.
How Is image appeared with a big hole of pinhole camera?
Answer:
We get blurred image on the screen due to big hole of the camera.

Question 3.
Which path light tends to prefer?
Answer:
Light selects the path which takes least time to travel.

Question 4.
What is meant by lateral inversion?
Answer:
The right appears as left in the image is called lateral inversion.

Question 5.
If an object placed in front of a plane mirror has size 6 cm, then what is size of the image?
Answer:
Size of the object = Size of image.
∴ Size of the image = 6 cm.

Question 6.
What is a real image? What is a virtual image?
Answer:
Real image: The image formed due to convergence of light rays. The real image can be caught on the screen.
Virtual image: The image that we get by extending the rays backwards is called a virtual image. A virtual image cannot be caught on the screen.

Question 7.
What is a reflecting surface?
Answer:
The surface used for reflection is called reflecting surface.

Question 8.
What is principal axis?
Answer:
The horizontal line which passes through the centre of curvature is called principal axis.

Question 9.
What is meant by converging of light rays?
Answer:
If light rays after reflection meet at a point, then we say the light rays are converging.

Question 10.
Why does our image appear thin or bulged?
Answer:
Due to converging or diverging of light rays from the mirror.

Question 11.
Why is angle of incidence equal to angle of reflection when a light ray reflects from a surface?
Answer:
Because light selects the path that takes least time to cover a distance.

Question 12.
Are angle of reflection and angle of incidence also equal for curved surface?
Answer:
Yes, it is equal for curved surfaces like spherical mirrors.

Question 13.
Why is there right-left inversion (lateral inversion) when we look into mirror?
(OR)
Explain the lateral (righ-left) inversion of the image in plane mirrors through an example.
Answer:

1. The light rays which come from object get reflected from the plane mirror and reach our eye.
2. Our brain feels that the ray is coming from the inside of mirror.
3. So there is right-left inversion.

Question 14.
What are the minimum conditions to get shadows?
Answer:
The minimum conditions required are a source of light to produce light, an opaque object to obstruct the light and a screen to collect the shadow.

Question 15.
What happens if we increase the size of the hole of the pinhole camera?
Answer:
If the size of the pinhole camera is increased, the image seems to be blurred.

Question 16.
Name some apparatus which can work on the principle of reflection of light.
Answer:
Plane mirror, spherical mirrors, periscope, kaleidoscope.

Question 17.
What is your opinion on elevating buddings with mirrors?
Answer:
The mirrors used in elevating buildings are reinforced, tough and laminated glasses. These mirrors provide safety and make the buildings attractive.

Question 18.
What happens when light falls on an opaque object?
Answer:
Some part of light is reflected back and remaining part is absorbed.

Question 19.
What happens when light is reflected from transparent object?
Answer:
Some part of light is reflected and remaining part is partly transmitted or partly absorbed.

Question 20.
If angle of incidence of light ray on a plane mirror is 40°, then what is the angle between incident ray and reflected ray?
Answer:
The angle between incident ray and reflected ray is 80°.

Question 21.
From the figure, find angle of reflection.

Answer:
The angle of reflection is 40°.

Question 22.
If distance of plane mirror and object is 10 cm, then what is the distance between object and its image ?
Answer:
Object distance = image distance
∴ Distance between object and image = 10 + 10 = 20 cms.

Question 23.
If the angle between the mirror and incident ray is 40°, then find the angle of reflection.
Answer:
Given that angle between incident ray and mirror = 40°.

Suppose angle of incidence = x.
∴ 40 + x = 90
x = 90 – 40 = 50°.
But we know angle of incidence = angle of reflection
Angle of reflection = 50°.

Question 24.
State Fermat’s principle.
Answer:
Light chooses the path which takes the least time to travel.

Question 25.
Can a virtual image be photographed by a camera?
Answer:
Yes, virtual image can be photographed by a camera.

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces 2 Marks Important Questions and Answers

Question 1.
What are the characteristics of image formed by a plane mirror?
Answer:
Characteristics of image formed by a plane mirror.

1. It is a virtual image.
2. The image is straight.
3. The image is laterally inverted.
4. Size of the image is equal to size of the object.
5. Image distance is equal to object distance.

Question 2.
Can a plane mirror ever form a real image?
Answer:

1. Real image can only be formed when the reflected rays converge.
2. For plane mirrors it is not possible.
3. However if the reflected rays are converged it can form a reed image.
4. Consider a source of light at infinity (say sun) and plane mirror is very small in size, its reflected image will show a circular bright spot (image of sun) on the screen.

Question 3.
Frame some questions on the importance of ‘perpendicular’ in the reflection of light.
Answer:

1. Why do we require perpendicular (normal) to a plane mirror?
2. If light falls normal to the surface of a plane mirror, what happens?
3. What is the importance of normal?
4. In this figure what is angle of reflection?
   

Question 4.
How is an image formed by a plane mirror?
Answer:

1. ‘O’ is a point object. Some rays from O reach the mirror and get reflected.
   
2. When we look into the mirror, the reflected rays seem to be coming from the point I. So point I is the image of point object ‘O’.

Question 5.
Draw the ray diagram of lateral inversion of a letter.
Answer:

Question 6.
Draw the ray diagram showing point object (O). (OR)
Draw the ray diagram showing an object (OO’) by a plane mirror.
Answer:

Question 7.
Observe the given figure. Write the values of angle of incidence and angle of reflection. Complete the figure using these values.

Answer:
The angle of incidence (i) = 90 – 60 = 30°
The angle of reflection (r) = 30°
(∵ angle of incidence = angle of reflection)

Question 8.
Draw the diagram that explains the formation of an Image by a plane mirror.
Answer:

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces 4 Marks Important Questions and Answers

Question 1.
Write briefly about formation of image by a plane mirror. Write characteristics of image. (OR)
A teacher asked a student which mirror is used by him to see his image at home. Then name that mirror and also give formation of image due to that mirror and characteristic of image formed by that mirror.
Answer:
Image formation for a point sized object:

1. ‘O’ is a point object. Some rays from ‘O’ reach mirror and get reflected.
2. When we look into the mirror, the reflected rays seem to be coming from the point I.
3. So T is the image of point ‘O’.
   
   Image formation of an object:
4. Now place an erect object in front of plane mirror.
5. Draw some incident rays from the object to the mirror and reflected rays from the mirror using laws of reflection.
6. The rays coming from the point ‘O’ and reflected from the mirror seem to be coming from point ‘I’.
7. So I is the image of ‘O’.
8. The rays coming from the point O¹ get reflected from the mirror and seems to be coming from point I¹. So I¹ is the image of O¹.
   
9. The rays coming from the middle part of the O and O¹ will form their images between I and I¹.
10. Thus I – I¹ is the image of the object O – O¹.

Characteristics of image:

1. The image has same size as object.
2. The image distance and object distance are same.
3. The image undergoes right-left inversion (lateral inversion).
4. The image is virtual and erect.

Question 2.
Why does the size of the image decrease when you move the object towards your eye?
Answer:

1. The given figure shows how our eye judges the distance of an object.
2. The object which is at point ‘O’ looks smaller to the observer 2 than to the observer 1 because the light rays coming from the object 1 makes a smaller angle at the eye of the observer 2 compared to observer 1.
   
3. The angle plays the role in sensing the size of the object.
4. Similarly, when we move the object from the mirror to our eye, the image in the mirror seems to move back in the mirror.
5. Then the distance from the image to our eye increases.
6. The angle formed by image at our eye is smaller than that of angle formed by the object.
7. That is why the image looks smaller than the object.

Question 3.
Why does a plane mirror act as better reflecting surface when compared with other reflecting surfaces? Why?
Answer:

1. When light falls on any surface some part of light is reflected by the surface, some other part is transmitted by the surface and remaining part is absorbed by the surface.
2. However, a reflecting surface like mirror reflects most of the light (nearly 90%) fallen on it.
3. A plane mirror is made by polishing or silvering one side of plane glass.
4. The side which is silvered called silvered surface while the other side is called reflecting surface.
5. The light always reflects from reflecting surface.
6. To protect the silver polish or silvered surface often it is painted with red or black colours.
7. This type of arrangement actually increases the reflection up to 90%. So it acts as better reflecting surface.

Question 4.
The figure shows a plane mirror PQ at distance 20 cm from an object. The mirror is moved 15 cm away from object O to next position. What is the shift in the image of O?

Answer:
Given that at first the object 20 cm from the mirror. So the image is also at a distance of 20 cm from mirror (Since object distance = image distance).
Now the mirror is moved 15 cm away from the object. So the image also moves 15 cm away from actual image distance before. So now the image distance is 35 cm. Therefore the image is 70 cm from the object.

AP State Syllabus AP Board 8th Class English Textbook Solutions Chapter 4A The Story of Ikat Textbook Questions and Answers.

AP State Syllabus 8th Class English Solutions Chapter 4A The Story of Ikat

8th Class English Chapter 4A The Story of Ikat Textbook Questions and Answers

Look at the pictures given and answer the questions that follow.

Question 1.
What do you see in these pictures? Where do you find them?
Answer:
In the first picture we see Kondapalli Bommalu. In the second picture we see the Rudrakshamalas (Chains of beads). In the third picture we see the statues of Vinayaka made with plaster of paris. We generally find these three kinds of handicrafts in stalls, shops, emporiums, exhibitions, etc. In the fourth picture we see Mayuri (Sudha Chandran), a famous Bharatanatyam dancer.

Question 2.
Why did the woman make up herself differently? Do you find anything unique in the make up of the woman in the picture? What could be the occasion for this make up?
Answer:
The woman made herself differently as she wanted to perform something. Yes, I find something unique in the make up of the woman in the picture. Usually women don’t make up themselves in such a way. It must be a special occasion. I think she was going to perform Bharatanatyam.

Question 3.
Are these handicrafts and the make up a part of our culture? Give reasons to your answer.
Answer:
Yes, these handicrafts and the make up are a part of our culture. Handicrafts promote our cultural heritage. They make the younger generations know our ancestry, the richness of culture and traditions. Since old ages, our land is famous for these handicrafts. The art forms such as Kuchipudi, Bharatanatyam etc., need the make up. These art forms originated in our country and there have been so many well known artists in our country. Hence, 1 can say that these handicrafts and make up are a part of our culture.

Comprehension

Answer the following questions.

Question 1.
What is the main theme of the story?
Answer:
The main theme of the story is making the children know the richness of our cultural heritage. The story of Ikat’ presents the present condition of textiles in Andhra Pradesh, the meaning of Ikat, the great skill of weavers behind weaving Ikat, the holiness of tying the knot and our traditions. It sends us a message that we should promote handicrafts and protect artists.

Question 2.
How is chitiki rumal used by different people?
Answer:
‘Chitiki Rumal’ is the favourite headgear of fishermen and other labourers. It is also used by Gujarat traders as the towel on their shoulders.

Question 3.
The teacher became silent when she was discussing handloom. Why?
Answer:
When the teacher was discussing handloom, she became silent because of the present status of it. She thought that we had forgotten our heritage in the race with the machine. So, she became serious in those kinds of thoughts.

Question 4.
Children’s attention was divided between her words and thefabrics as she opened silk patola sari. Why?
Answer:
The teacher used the words such as Chitiki, Patola and Ikat to explain the handloom. Saying these words, she opened a silk patola sari from Patan, Gujarat. It had a red design on a black background with rows of flowers in the border. The simple leaf design repeated across the body and the flowers in the border created a mesmorising effect. So, their attention was divided between her words and fabrics.

Question 5.
The writer described some designs, historical things and the weaving. Which part of the story do you like most?
Answer:
I like the process of weaving the most as it is a complex process. Counting the threads, measuring the distance, calculating when to repeat a pattern and tying the knot seem that it is a complex process.

Vocabulary

I. Read the following sentences.
V.V.S. Lakshman is a top class batsman.
Sruthi is in class VIII.
We have ten minutes left for the show.
The minutes of every official meeting remain an important document.
The words underlined in the above sentences have the same spelling but they differ in meaning. These words are called Homonyms.

Find the meaning of the following homonyms with the help of a dictionary.

1. a) fair (adj): ——————————-
b) fair (noun): ——————————-
2. a) mind (noun): ——————————-
b) mind (verb): ——————————-
3. a) quiet (adj): ——————————-
b) quiet (noun): ——————————-
Answer:
1. a) fair (adj): acceptable and appropriate in a particular situation
b) fair (noun): a large public event where goods are bought and sold; a type of entertainment in a field or park
2. a) mind (noun): the part of a person that makes them able to be aware of things, to think and to feel
b) mind (verb): to be upset, annoyed or worried by something
3. a) quiet (adj): making very little noise
b) quiet (noun): the state of being calm without much noise

II. Use the above homonyms In your own sentences.
Answer:
1. a) He is very fair always.
b) This evening we are going to the fair.
(or)
This evening we will go to the fair.
2. a) She is in a disturbed state of mind,
b) I hope you don’t mind if I leave now.
3. a) All the class is very quiet.
b) He always loves the quiet of his own room.

III. Read the following sentences carefully.
The students have some knowledge about ‘Ikat’.
This sum from chapter III is very tough.
The words underlined in the above sentences have the same pronunciation but differ in spelling and meaning. Such words are called Homophones.
Read the following passage carefully and replace the underlined words with correct homophones.
One day Janaki teacher said to the class, “We all no that the boy in the blew dress has one the best student price for this year.” She added this is the write hour to felicitate him. Here is the gift for the boy but can anyone help me to untie the not of the died ribbon. One boy came forward and helped her. There is a wonderful gift inside the box!
Answer:
One day Janaki teacher said to the class, “We all know that the boy in the blue dress has won the best student prize for this year. ” She added this is the right hour to felicitate him. Here is the gift for the boy but can anyone help me to untie the knot of the dyed ribbon. One boy came forward and helped her. There is a wonderful gift inside the box!

Grammar

I. Read the following pair of sentences taken from the narrative “The Story of Ikat”.
1. Ramya asked, “Are these fabrics from Indonesia?”
2. The teacher said, “What can be the origin of the word?”
a. Who are the speakers?
b. What are the exact words spoken by them?
c. If you want to report the above sentences, how will you do?
Let’s analyse the sentences 1 and 2.
The first part of the sentence ‘Ramya aksed’ has a subject ‘Ramya’ and a verb ‘asked’.
This clause is called the reporting clause. The verb is called reporting verb.
The part within the quotation marks is called reported clause, which gives the exact words spoken by the speaker.
Let’s look at the answer to the question ‘c’.
1. Ramya asked if/whether those fabrics were from Indonesia.
2. The teacher asked what the origin of the word could be.
Let’s look at the changes that have taken place.
You will find the following changes.
a. Change of the pronoun (these – those)
b. Change of the verb in the reported clause (are – were)
c. Change of question to a statement by adding if/whether
All the above changes are made when the reporting verb is in Past tense.
1. Report the following conversation.
Ramya visits a weaver at Pochampally. She asks him a few questions.
Ramya : Uncle, What are you doing?
Weaver: I’m making a sari. Do you like it?
Ramya : Oh! Yes. What is the price?
Weaver : Five hundred rupees. Do you want to buy it?
Ramya : Oh! Yes. Can you pack it for me?
Weaver : Sure, here you are.
Answer:
Ramya asked the weaver what he was doing. He replied that he was making a sari. He asked her if she liked it/that. Ramya replied affirmatively and asked him what the price was. He replied that it was five hundred rupees and asked her if she wanted to buy it/that. Ramya replied affirmatively and asked him if he could pack it/that for her. He replied that he could certainly give it and then offered her the sari she wanted.

Look at the following changes while reporting.

WASH AWAY THE GERMS
Washing hands helps prevent the spread of germs, and should be done frequently.

• Before you eat.
• Before and after you help a sick person.
• Before you care for a wound or cut, and again after.
• After you use the toilet.
• After you cough, sneeze or blow your nose.
• After you handle animal waste or an animal or pet treats/food.

The Story of Ikat Summary in English

Janaki was a Social Studies teacher. That day she came a bit late to the class. She brought the brilliant red and black checked rumals, shawls with black and blue geometric patterns with her. That material made the dull class vibrant. She wrote on the blackboard ‘Textiles of India – “Ikat” of Andhra Pradesh and pronounced the word “Ikat”. “Ikat” means “to bind” or “knot”. Then she elicited the name of Nalgonda district from the students. She made them know the name ‘Pochampally’, a village in Nalgonda district in connection with “Ikat”. Every student immediatley connected to the village. A handloom is a hand operated loom which weaves. It has been weaving fabrics for centuries. Now we have forgotten our heritage in race with the machine. After telling this, Janaki began to tell the story of Ikat. It is called ‘Chitiki’ in Telugu, ‘Patola’ in Gujarati and simply ‘Ikat’ in Oriya. She showed them a silk patola sari from Patan, Gujarat which created a mesmerising effect. Then she asked them if they were thinking about ‘Ikat’ or ‘tie and dye’. When no one could answer her, she told them about ‘warp’ and ‘weft’. The threads stretched lengthwise are called ‘warp’ and the threads intersecting them widthwise are called ‘weft’. In ‘Ikat’ the threads are carefully sorted, warp and weft divided into bundles, then tied with the materials like plastic sheets, rubber strips and then dropped into colours. The weavers count the threads, measure the distance, calculate when to repeat a pattern and then tie the knots. They draw patterns on the graphs and copy them on the threads. ‘Chitiki rumal’ was the favourite headgear of fishermen and other labourers. Gujarat traders put them on their shoulders as the towels. In Telugu ‘Chitikedu’ means a small quantity of material. Then the students came to know about the original explanation of Ikat. They understood that the characteristic of Ikat was small and small dots of colour. Once Chitiki fabric was our favourite export item. There are different stories about its origin. Different regions fight about its origin but there is no systematic documentation to resolve this dispute. Tying the knot is sacred in our tradition. Muslim culture influenced the designs in Ikat in parts of Gujarat, Maharashtra and Deccan.

The Story of Ikat Glossary

mandatory (adj): compulsory

wonder (v): wish to know

drab (adj): dull

pelt (v): throw; shoot

giggle (v): laugh in a silly way

babble (n): a talk difficult to understand

pensive (adv): serious

hesitantly (adv): unwillingly/uncertainly

expectantly (adv): hopefuL of something

intersect (v): crossing each other at a point

headgear (n): a piece of cloth worm on head

jubilant (adj): very happy

resolve (v): solve

knot (n): fastening

vibrant (adj): active

compelling (adj): extremely interesting

dashed (v): went somewhere very quickly

partial (adj): showing or feeling too much support for one person, team, idea, etc.

persisted (v): continued

criss-cross (v): to make a pattern on something with many straight lines that cross each other

motif (n): a design or a pattern used as a decoration

sorted (v): arranged things in groups or in groups or in a particular order according to their type

vigorous (adj): very active, determined

origin (n): the point from which something starts

AP State Syllabus AP Board 8th Class English Textbook Solutions Chapter 1C A Letter to a Friend Textbook Questions and Answers.

AP State Syllabus 8th Class English Solutions Chapter 1C A Letter to a Friend

8th Class English Chapter 1C A Letter to a Friend Textbook Questions and Answers

Comprehension

Answer the following questions.

Question 1.
How did Suresh and Ramesh spend their time?
Answer:
Suresh and Ramesh enjoyed their childhood days in Manikonda village. Every day they played gilli-danda, hide and seek and kabaddi in their garden. They played in the moonlight. They enjoyed listening to the tales told by their grandpa. Thus they spent their time joyfully.

Question 2.
Why did Ramesh’s family move to the city?
Answer:
Ramesh’s family moved to the city as both Ramesh and his wife got jobs in the city (Hyderabad). They got jobs in software companies.

Question 3.
What change did you observe in Ramesh?
Answer:
Ramesh enjoyed his childhood days along with his friend Suresh in Manikonda village. There were so many unforgettable, joyous occasions in their childhood. They leisurely spent their time enjoying the beauty of the nature. But now he is not happy in city. He is annoyed at his busy city life. He is the man of disgust. Ramesh’s family members hardly find time to sit together. They have forgotten their family. They work like machines. They have missed the joy of the family, their company and many things in the busy life.

Question 4.
Do you think Ramesh is happy in the city? Why?
Answer:
No. I don’t think Ramesh is happy in the city. He thinks that his city life is very disgusting. Both Ramesh and his wife work at software companies. They don’t find any time to sit together. They are always busy. They work with computers, think like computers and live like computers. They have forgotten their family. Ramesh recalls all the joyous occasions he had during his childhood. He thinks that he has missed his relatives, the joy of the family, their company and many things in his busy life. He thinks that their flat is their world, just like a well for a frog.

Question 5.
What made Ramesh write to Suresh?
Answer:
As Ramesh had a meeting in his office, he didn’t meet his friend Suresh during his visit to Hyderabad the previous week. So, he wrote a letter apologizing for his not meeting Suresh.

Proect work

Observe any five families in your neighbourhood and draw your conclusions, ad¬vantages and disadvantages of living in a joint/nuclear family.
Answer:
I observed five families living in our neighbourhood. All the families are nuclear ones that consist of a man, his wife and their children.
In the present society the concept of the joint family system has been gradually breaking up. In its place a new system of nuclear family has aroused. I think both types of families have their own merits and demerits. The joint family system is a feature of agricultural societies. Collective living, collective planning and collective share in family wealth are the traditional features of the joint family. We can see the division of labour in a joint family. The joint family preserves the traditions, customs and values and passes them down to the next generations. With the passage of time, the joint family system has disintegrated, giving rise to the nuclear family system.
The nuclear family consists of a man, his wife and their children. Job opportunities available in the cities become the main cause of the disintegration of the joint family system. For a number of reasons, a joint family system doesn’t exist in the cities. There is a lack of living space in the cities. It is difficult to accommodate all the members of a joint family in a single house in the city. The cost of living is very high in the cities. The increasing individualistic and independent attitudes of grown up children give rise to the nuclear family system. Now, we see advantages and disadvantages of living in both the families.

Advantages of living in a ‘joint family’

1. Joint family helps the younger ones to develop social virtues like co-operation, sympathy, sacrifice, affection, selfless service, obedience and broad minded nature.
2. Each member of a joint family is given work according to his or her capacity. Hence, we find division of labour in a joint family.
3. There is more affection and love among family members.
4. Joint family affords ample leisure to its members.
5. Joint family acts as an agency of social control.
6. In the joint family the children the employed, the sick, the aged and the handicapped are well taken care of.
7. We find sharing of sorrowness in a joint family.

Disadvantages of living in a ‘joint family’

1. There is no privacy.
2. There is no financial independence.
3. There is a chance for disharmony due to generation gap.
4. There may be chances for conflict between males and females and the young and the old due to diverse temperaments.

Advantages of living in a ‘nuclear family’

1. Nuclear family provides more privacy.
2. The members of a nuclear family have financial independence and stability.
3. The members of a nuclear family have more freedom.
4. The members of a nuclear family find no stress and discomfort.

Disadvantages of living in a ‘nuclear family’

1. If both the parents are employees, they find no time to care for the children.
2. The members of a nuclear family feel insecure.
3. There may be extra expenses in a nuclear family.
4. The members of a nuclear family lose the support and experience of the elders.
5. There is no sharing of sorrows.

A Letter to a Friend Summary in English

Ramesh wrote this letter to his friend Suresh apologizing for his not meeting him during his visit to Hyderabad the previous week. Ramesh is a computer programmer at Microsoft, Hyderabad and his wife is a System Analyst at Dell, Hyderabad. He is annoyed at his busy city life. Both Ramesh and his wife work with computers, think like computers and live like computers. Their child always plays computer games never caring for anyone. Ramesh is very unhappy in the city. He recalled the memorable days of his childhood in his letter. Ramesh and Suresh enjoyed their childhood days in Manikonda village. They played together in their garden in the moonlight. Theirs was a big family. Their grandpa used to tell them tales. They played gill-danda, hide and seek and kabaddi. They went for swimming every Sunday. Ramesh remembered how their Padmanabhaiah Sir appreciated them when they got the first prize in District Science Fair. Their picnic to Koil Sagar and their tour of Srisailam were memorable. Ramesh couldn’t forget the roaring of the Krishna River at the dam. They enjoyed the festivals such as Dasara, Deepavali, etc. along with their uncle and aunt. Ramesh thought of his grandparents, uncles, aunts, brothers, sisters …. sometimes. He thought that they missed them all. They missed the joy of the family, their company and many things in their busy life. At present they are living in this unreal world. They have lost their real life.

A Letter to a Friend Glossary

faded (adj): pale

hardly (adv): almost never

disgusting (adj): extremely unpleasant

appreciated: understand the worth of

company (n): the fact of being with somebody else and not alone

affection (n): a feeling of liking for a person

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 8 Combustion, Fuels and Flame Textbook Questions and Answers.

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

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

Improve Your Learning

Question 1.
Give four examples of combustible materials.
Answer:

1. Petrol
2. Diesel
3. Kerosene
4. Alcohol

Question 2.
Give four examples of non-combustible materials.
Answer:

1. Sand
2. Clay
3. Iron
4. Steel

Question 3.
Why should not we store spirit or petrol near our living place?
Answer:
Spirit or petrol has low ignition temperature. So they turn into gas at room tempera¬ture. So they are highly inflammable that means they easily catch fire at room temperature. So in order to avoid fire accidents we should not store spirit or petrol near our living place.

Question 4.
Give an example of a good fuel. How do you choose that fuel? Explain.
Answer:
The example for good fuel is CNG.
The characteristics of good fuel.

1. It should be cheap.
2. It should be readily available.
3. It should be readily combustible.
4. It should be transported easily.
5. It should have high calorific value.
6. It should not produce gases or residue that pollute the environment.

CNG possess all these characteristics so it is an example for good fuel or ideal fuel.

Question 5.
The oil tires should not be sprayed with water. Why?
Answer:
We should not spray water on oil fires because water is heavier than the oil, it sinks below the oil and oil keeps burning on the top. So water is not suitable for oil fire accidents.

Question 6.
What precautions are to be taken while pouring water on fire?
Answer:

1. Put off the electric mains.
2. Do not pour water on fires caused by electricity water containing dissolves salts is a good conductor of electricity.
3. Do not pour water on fires due to petrol and oil because water is more denser the u oil and petrol.

Question 7.
Why a wick is not used in gas burners ?
Answer:
Wax in the candle melts when it is lighted by a match and a little wax forms vapour. This vapour combines with oxygen in the air to form flame. The heat of the flame melts more of the wax from the top of the candle. The melted liquid wax move upward through the thread. It also changes to vapour when it reaches the top the wick and burns w’ h the flame.
Wick is not required in gas burners because LPG has low ignition temperature so it is easily convert into vapour state.

Question 8.
Water is not used to control fires involving electrical equipment. Why?
Answer:
Water is not used to control fires involving electric equipments because water is good
conductor of electricity (water having dissolved salts) so it may conduct electricity and harm those trying to douse the fire.

Question 9.
Give supporting arguments for both the statements (1) fire is useful (2) fire is harmful.
Answer:
Fire is useful:

1. Fire is useful in cooking food.
2. Fire is used in preparing different types of jewellery with gold and silver.
3. Fire is utilized in making different types of articles with metals and plastics.
4. The heat energy produced from fire of coal used to produce electricity.

Fire is harmful:

1. During fire accidents fire can burn human organs and tissues causing severe damage to mankind, sometimes the people may die due to severe burns.
2. During fire accidents the fire not only kill people but lot of damage to articles, equipments in the house.
3. Fire can burn the forests in summer which may be harmful to animals present in the forest.

Question 10.
What would happen if oxygen stops to support combustion? – Make a guess. And if it is the situation for what other works 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 11.
Let us assume that you are on the moon. If you try to focus sunlight on a paper using magnifying glass, does the paper catch fire? or not? Why?
Answer:
No, moon reflect entire sunlight 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 12.
Can you heat water in a paper vessel? How is it possible?
Answer:
In order to find the answer we have to do an experiment.

Take two small paper cups. Pour water in one of the cups. Put the two cups on different tripod stands and heat both of them using a candle shown in the figure. One cup burns quickly and other does not.
The reason is when heat is supplied to cups, the heat received by second cup is transferred to water
in it. The water in this cup prevents the paper to reach its ignition temperature and hence it does not burn. So water can be heated in a paper vessel upto ignition temperature of paper.

Question 13.
“Is combustion possible without the supply of oxygen”? Discuss with your teacher.
Answer:
No, combustion is not possible without oxygen because it is a reaction of material with oxygen that is an oxidation process. For example, carbon compounds react with oxygen and form carbon-dioxide and water. So no combustion reaction is possible without oxygen.

Question 14.
Explain giving reasons: In which of the following situations water will get heated in a shorter time?
a) Srikar kept water beaker near the wick in the yellow part of a candle flame.
b) Sonu kept water beaker in the outermost part of the flame.
Answer:
In the second situation water will get heated in a short time in the outermost part in the flame complete combustion takes place so which is hottest part whereas yellow part is in the middle zone of candle where partial combustion takes place and it is moderately hot.

Question 15.
List the ways adopted by fire fighters to combat fires.
Answer:
Ways adopted by fire fighters:

1. The fire fighters immediately put off the electric mains and start spraying water on the fire. The water spray cool the combustible material below the ignition tempera¬ture. This prevents fire from spreading. Then the heat turns the water into vapours which surround the burning material and prevent supply of oxygen to the burning material. So the fire extinguishes.
2. For electrical fire accidents or fire accidents involving oil and petrol water is not useful. So fire fighters use carbondioxide. It is heavier than oxygen and does not affect the electric equipment.

Question 16.
Collect information available on different fuels. Find out the cost per kg and compare the cost with calorific value. Prepare report on that.
Answer:

From the table we will observe CNG has least price and also comparatively equal calorific value with other fuels and also it is less pollutant and easily transportable. So from the report we say CNG is preferable as fuel.

Question 17.
Draw the diagram of candle flame and label all the zones. (OR)
Draw the diagram of structure of flame and label the parts. In which zone incomplete combustion takes place? (OR)
Draw a diagram of candle flame and label all the zones. What happens in the dark zone of a flame?
Answer:

In the dark zone wax gets vapourised and it is least hot part, (or)
In black zone in complete combustion takes place.

Question 18.
Where do you find spontaneous combustion and rapid combustion in your daily life?
Answer:
Spontaneous combustion is observed in burning of match stick. When the match stick is struck against the rubbing surface the red phosphorous converts into white phosphorous which immediately react with potassium chlorate in the match stick head to produce enough heat to ignite antimony sulphide and start the combustion.
Rapid combustion is observed in gas stoves. When we turn the nob of the gas stove in the kitchen and bringing a burning match stick near to it. The gas burns rapidly and produce heat and light.

Question 19.
How do you organize your daily works with fuels to conserve bio-diversity?
Answer:

1. I would use bicycle to travel short distances which consumes fuel.
2. I would go to school or office (long distance) in a public vehicle like bus which will consume fuel.
3. I will drive at a constant and moderate speed as far as possible which will consume fuel.
4. I switch off the engine at traffic lights or at a place where I have to wait which will consume fuel.
5. I ensure correct tyre pressure which will consume fuel.
6. I ensure regular maintenance of the vehicle which decreases the harmful gases.
7. I will clean gas burners regularly which decreases pollution.
8. I will cook with sufficient water which will consume fuel.
9. I would not prepare fries which take more time.
10. I will use CNG in place of petrol or diesel which is less pollutant.
    The above steps not only reduce the consumption of fuel and also decrease the air pollution. These steps of preserving fuels helps the mankind from pollution there by helps the bio-diversity.

Question 20.
How do you feel about “Fuels have become a part of human life”
Answer:
I feel that fuels are essential part of human life in their day to day life. Starting from the morning before they going to sleep they would found application of fuels. In the morning for breakfast we need fuel for cooking. For seeing TV or working with computer we need fuel because they run by electricity from thermal power (coal). If we want to go to school or office we use vehicle which required fuel. Every electrical articles like fans, mixies works by taking electricity from coal. So we conclude that fuels are essential part of human life.

Question 21.
It is difficult to bum a heap of green leaves but not a heap of dry leaves. Explain why?
Answer:
Green leaves contain water has high ignition temperature. So it will not burn whereas dry leaves does not contain water. So their ignition temperature is low. So they burn during summer.

Question 22.
In a few years the fuels on earth will be exhausted. Think, what would happen to human civilization? (OR)
In few years the fuel on earth will be exhausted. Predict the consequences.
Answer:
If people unable to use alternative sources of energy then lack of fuels drastically affect the human civilization. The consequences of lack of fuel.

1. There would be no fuel for cooking.
2. There would be no fuel for transport.
3. There would be no fuel for running machinery.
4. There would be no fuel for producing electricity.

So life of people on earth is miserable. The people once again go back to stone age where there is no availability of any facilities.

Question 23.
Use of more fuels in our daily life causes air pollution and it is harmful to human being and the other life on earth. Suggest some remedies to avoid this.
Answer:
Remedies to avoid air pollution:

1. Look for alternative sources of energy like wind energy, solar energy, tidal energy which does not produce pollution.
2. Try to minimise the use of fuels that is for travelling short distances use bicycles and try to go by bus (public transport) for offices which will minimise the use of fuels and there by air pollution.
3. Ensure regular maintenance of vehicle and engine which will release the less quantity of harmful gases there by decrease of air pollution.
4. Use CNG (compressed natural gas) as fuel as it is less pollutant and release small quantity of harmful gases.

Question 24.
Project work: Collect information about the experiments of Joseph Priestly. Write a two page report describing Priestly’s experiments proving that oxygen is needed for burning.
Answer:
In August 1774, Priestly isolated an air to be completely new, but he did not have an opportunity to pursue the matter because he was about to tour Europe. While in Paris Priestly managed to replicate the experiments for others, including French chemist Antonie Levoisier. After returning to Britain in January 1775, he continued his experiments and discovered vitriolic acid air (Sulphurdioxide, SO₂).
In March he wrote to several people regarding the new air that he had discovered in August. One of these letters was read aloud to the royal society, and a paper outlining the discovery, titled “An Account of further Discoveries in air”, was published in society’s journal “Philosophical Transactions”. Priestly called the new substance “dephlogisticated air” which he made in the famous experiment by focussing sun’s rays on a sample of mercuric oxide. He first tested it on mice, who surprised him by surviving quite a while entrapped with the air, and then on himself, writing that it was “five or six better than common air for the purpose of respiration, inflammation and I believe, every other use of common atmospherical air. He had discovered oxygen gas (O₂).”
Priestly called his discovery “dephlogisticated air” on the theory that it supported combustion so well because it had no phlogiston in it and hence could absorb maximum amount during burning.

Question 25.
Collect the information about annual fuel consumption in different parts of the world. How many years more the fossil fuels last? Make a poster with this information and issue an appeal to save fuel.
Answer:
Table showing different countries and their petrol consumption.

The information showing the remaining years in which fossil fuels exhausted.

We are using excess of petroleum products, coal and natural gas from the above table shows they will not exists long. So fuel consumption should be minimised otherwise no fuel is available in the future. So save fuel for better living.

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

8th Class Physical Science Textbook Page No. 110

Question 1.
Why does candle give flame when it is burnt but why does coal burn without emitting a flame?
Answer:
A candle is made of wax in which a thick thread is inserted. When it is lighted melts by a match stick. A little of the wax forms gas. This gas combines with oxygen in the air to form flame.
But coal is a natural fuel contains more carbon. When it is burnt it sends out carbon monoxide and carbon dioxide gases and becomes ember and does not emit a flame. Coal is the changed material of wood. Hence it does not emit a flame as it possesses a huge calorific value (heat).

Question 2.
Do all fuels produce same amount of heat when they are burnt?
Answer:
No, different fuels produce different amount of heat when they are burnt.

Question 3.
What do we need to burn a material?
Answer:
We need oxygen to burn a material.

Question 4.
Have you ever tried burning a piece of paper or wood or coal, a small rock or a pebble?
Answer:
Yes, I tried.

Question 5.
Do all of them burn?
Answer:
Except a small rock and a pebble, the rest of them are burnt.

8th Class Physical Science Textbook Page No. 112

Question 6.
How does scented stick started burning?
Answer:
The stick starts burning with flame because oxygen supports combustion.

Question 7.
Why does not it catch again fire when it is kept aside in air after putting its flame off?
Answer:
The air is not sufficient to burn the scented stick.

8th Class Physical Science Textbook Page No. 113

Question 8.
a) A slow fire bursts into a flame when air is blown on it, but a candle burning with flame goes off when air is blown on it. Why?
Answer:
A slow fire burst into a flame when air is blown on it because it increase the supply of oxygen to fire. So combustion takes place to produce a flame.
Whereas when the wind or your breathe blows on the mixture of combustible particles and flame of a candle, it pushes the mixture of combustible particles away from the steam of fresh particles. So flame will be go out in the absence of combustible particles.

b) If a large quantity of dry grass is set on fire in forests then it is very difficult to put off the fire. Why?
Answer:
The dry grass is more combustible and supports burning. Hence due to the flow of oxygen (air) it is kindled.

Question 9.
When an object catches fire, the fire is put off by covering with sand or a blanket. Why ?
Answer:
Combustion takes place only in the presence of oxygen. When we cover a burning object with sand or blanket that would cut off the supply of oxygen to burning object. So the fire is puts off.

8th Class Physical Science Textbook Page No. 114

Question 10.
What makes match sticks to catch fire?
Answer:
A mixture of antimony trisulphide, potassium chlorate and white phosphorous with some glue and starch was applied on the head of a match stick made of suitable wood. When it struck against a rough surface white phosphorous got ignited due to heat of friction. This starts the combustion of match stick.

8th Class Physical Science Textbook Page No. 115

Question 11.
List different fuels that are used for!
Domestic purpose LPG, CNG
Automobiles/ Aircraft/ Trains/ Rockets Petrol, gasoline
Industry Coal, Charcoal, wood, natural gas
Classify the above fuels into solid, liquid, gases and write them in table.

Look at the fuels in the above table.

Classify the above fuels into solid, liquid, gases and write them in table.

a) Can you decide the best fuel among them?
Answer:
CNG, LPG.

b) What is the criteria to decide a best fuel?
Answer:
CNG & LPG burn completely. The fuel which burns completely is the best fuel.

8th Class Physical Science Textbook Page No. 116

Question 12.
What is calorific value? Write its units.
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 kJ/kg.

Question 13.
How can we put off the fire if it breaks out?
Answer:
We can put off the fire by using the fire extinguishers in which CO₂ gas is present.

Question 14.
How water helps in eliminating the factors, which support the combustion?
Answer:
The water spray cools the combustible material so that its temperature decreases. This prevents the fire from spreading.

Think and Discuss

8th Class Physical Science Textbook Page No. 111

Question 1.
Why some materials burn and why some do not? Give reasons.
Answer:
Burning is a process of reaction of a material with oxygen. The materials which have weak molecular bonds easily react with oxygen so they burn easily. The material which have strong molecular bonds does not react with oxygen easily because the molecular bonds should be broken before they react with oxygen.

Question 2.
Why some materials which do not burn at normal temperature burn at higher temperatures?
Answer:
Burning is a process of reaction of a material with oxygen. The material which have strong molecular bonds does not undergo burning because the molecular bonds should be broken in order to react the material with oxygen. So they have high ignition temperature. So the materials which do not burn at normal temperature burn at higher temperature.

8th Class Physical Science Textbook Page No. 112

Question 3.
If you lift the glass tumbler (which is placed over a burning candle) to 1 cm height what happens? Why?
Answer:
The Candle tends to burn because of availability air containing oxygen because cool air is more denser than hot air.

8th Class Physical Science Textbook Page No. 113

Question 4.
How do you say that the gas released in the above experiment is oxygen?
Answer:
If we put a burning match stick into the container having oxygen it burns with bright flame the reason is oxygen supports combustion.

Question 5.
Can we replace potassium permanganate with any other substance to release oxygen?
Answer:
We can replace with HgO (Mercuric oxide), KClO₃ (Potassium chlorate), H₂O₂ (Hydrogen peroxide), NaNO₃ (Sodium nitrate), KNO₃ (Potassium nitrate) for release of oxygen.

Question 6.
Is there any other procedure to prove that oxygen is needed for burning?
Answer:
We can put off a fire by covering with sand or blanket because we are preventing supply of oxygen. So we can say oxygen is needed for burning.

8th Class Physical Science Textbook Page No. 115

Question 7.
Why is phosphorous preserved in water? (Hint: Think about the role of ignition temperature in combustion)
Answer:
Phosphorous is highly reactive with air containing oxygen. It has low ignition temperature. So it catches fire at room temperature. So it is preserved in water.

Question 8.
Why kerosene stoves and Bunsen burners have small holes in them? (Hint: Think about the role of air in combustion)
Answer:
Kerosene stoves and bunsen burners have small holes for entry of air for combustion of fuel.

Question 9.
It is hard to ignite match stick in rainy days. Why?
Answer:
It is hard to ignite match stick in rainy days because water has extinguishing property.

8th Class Physical Science Textbook Page No. 118

Question 10.
A wax candle burns with a yellow flame. The domestic gas burns with a blue flame. Why?
Answer:
The wax candle burns with a yellow in the middle zone because it undergoes partial combustion whereas domestic gas burns with a blue flame because it undergoes complete combustion.

8th Class Physical Science 8th Lesson Combustion, Fuels and Flame Activities

Activity – 1

Question 1.
Do all materials bum?
You will need a pair of tongs, some metal or clay dishes and a candle or a spirit lamp. Using tongs, pick up a small piece of paper and bring it near to the lighted candle and keep it on flame as shown in figure.

Record your observations in table.


Carry out this experiment with a piece of charcoal, magnesium ribbon, straw, cotton cloth, nylon cloth, dry wood, pebble, wax, plastic piece, etc. and record your observations.
You can try to burn liquids like water, petrol, diesel, alcohol and note down your observations in table.
Take 2 ml of water in small plate. Bring the lighted stick near to water in plate.
a) What do you observe in your attempt of burning water?
Answer:
Water does not burn.

b) Is there any difference in flame of lighted stick?
Answer:
If we brought near to water plate the flame decreases.

c) What happened to the lighted stick when it is brought closer to water in the plate?
Answer:
The water in the plate puts off.the lighted stick.
Carryout this activity using coconut oil, mustard oil, kerosene, etc. Record your observation in the above table.

d) What can we conclude from this activity?
Answer:
We conclude that some materials burn and others do not.

e) Which of the material in the above activity are combustible?
Answer:
Except pebbles and water remaining materials are combustible.

Activity – 2

Question 2.
Testing the necessity of air for burning.
Answer:

Take a small burning candle and put it on a table. Invert a glass tumbler over it.
The candle continues to burn for some time. Then flickers and finally flame goes off.
Remove the tumbler and again light the candle. Put the tumbler back over the candle. When the candle flame begins to flicker, remove the tumbler. What happens to the candle?
We find that putting the glass tumbler over the candle cuts off the supply of air and candle flame goes off. When the flame just begins to flicker if we removes tumbler the flame retains back due to supply of oxygen.
This experiment proves that air is needed to burn a material.

Lab Activity

Write an activity to prove that oxygen helps in burning. (OR)
How can you perform the acitivity to prove that Oxygen is essential for burning? Explain.
Answer:
Aim: To prove that oxygen helps in burning.
Material required: Test tube, test tube holder, spirit lamp, match box, inscence stick (agarbatti), potassium permanganate (KMnO4) crystals.
Procedure:
Light a scented / incense stick and let it burn for 10 seconds, then put out the flame and keep it aside.
Take potassium permanganate (KMnO₄) in a test tube. Hold the test tube with a test tube holder and heat it over the flame of spirit lamp. Oxygen is released on heating of potassium permanganate (KMnO₄).
2 KMnO₄ → K2MnO₄ + MnO₂ + O₂ ↑
Insert the agarbatti with the burning stub into the test tube as shown in figure.

Observations: The stick burns with a flame. This proves that oxygen supports combustion by helping agarbatti to burn with bright flame.

Activity – 3

Question 3.
Burning a paper with sun rays.
On a sunny day, go out and focus the sun rays on a piece of paper using a magnifying lens.

a) Touch the spot after some time. How do you feel?
Answer:
It is hot.
You must have heard about people in ancient times rubbing the pieces of stones together to produce sparks.

b) Have you tried it?
Answer:
Yes.

c) Rub two stones together hardly and touch them. What do you feel?
Answer:
They become hot.
Now recall some of your experiences:

d) Does a matchstick burns by itself?
Answer:
No.

e) Why do you rub the match stick on the side of the matchbox to bum it?
Answer:
When we rub match stick on the side of the match box due to friction it produces it which will burn the match stick.

f) Can you bum a piece of wood by bringing it close to a lighted matchstick?
Answer:
No.

g) Why do we use paper pieces or kerosene oil to start fire in wood or coal?
Answer:
Paper or Kerosene oil has low ignition temperature. So they are used to burn wood or coal which have higher ignition temperature.

Activity – 4

Question 4.
Understanding ignition temperature.
Take two small paper cups. Pour water in one of the cups. Put the two cups on different tripod stands and heat both of them using a candle.

a) Which cup bums first?
Answer:
The cup which does not have water.

b) Does the water in the cup become hot? Why?
Answer:
The water in the second cup is hot because the heat received by second cup is transferred to water in it. The water in this cup prevents the paper to reach its ignition temperature and hence it does not burn.

c) When does the second cup start burning?
Answer:
When it reaches its ignition temperature.

Activity – 5

Question 5.
Observing the behaviour of different solid fuels.
Collect some fuels like candle, coal, charcoal, magnesium ribbon, wood, cakes of cow-dung, camphor, wick of the oil lamp, wick of kerosene stove, domestic gas, etc. Burn each of them one by one with the help of spirit lamp and note the time they take to catch fire. Also observe how do they burn?
a) Do all of them bum in the same manner? If not, what difference do you notice?
Answer:
No, some of them produce flame and some does not produce flame.

b) Do all of them form a flame while they are burning?
Answer:
No, all of them does not form flame.
Record your observation in the following table

You may observe that a candle burns with flame whereas charcoal does not. Some materials burn with flame, some do not. Kerosene oil and molten wax rise through the wick become gas and form flames. But charcoal cannot be vaporized. So it does not produce flame.

Activity – 6

Question 6.
Observing the structure of the flame.
Light a wax candle and watch the flame.

Carefully note the different coloured zones in the flame.
a) How many colours are there in the flame?
Answer:
There are three colours in the flame.

b) Starting from the base of the flame, how many flame zones do you observe?
What is the colour of the outer most zone of the flame?
Answer:
There are three flame zones are observed.
The colour of outermost zone is blue.

c) Observe the innermost zone which is dark. What do you observe there?
Answer:
In this zone wax gets vapourised. This is dark zone.
Observe near the base of the flame. Vaporized wax gets completely oxidized and burns with a blue flame. It is blue zone.

Activity – 7

Question 7.
Observing what happens in different zones of candle flame.
Light a candle. Hold a glass tube (with 7 cm length) a pair of tongs and introduce its one end in the dark zone of a non flickering candle flame. Keep lighted match stick near the other end of the glass tube as shown in the figure.

a) What do you observe? Do you see a flame? If so what is it, that produces a flame?
Answer:
Yes, the some of vapours produced by wax pass through the glass tube and are burnt by match stick to produce flame.

b) Notice that the wax near the heated wick melts quickly. What do you observe?
Answer:
When the candle’s flame is steady introduce a clean glass slide into the luminous zone of the flame and hold it with a pair of tongs for 10 seconds.
A blackish circular ring is formed on the glass slide.

c) What is it?
Answer:
The deposition of unburnt carbon particles present in the luminous zone of the flame due to incomplete combustion.

d) Hold a thin long copper wire just inside the flame for about half a minute. What do you observe? What is your inference?
Answer:
The copper wire just outside the flame gets red hot. It indicates that the non luminous zone of the flame has high temperature. It is the hottest part of the flame. It is blue in colour and complete combustion takes place due to good supply of oxygen.

AP State Syllabus AP Board 8th Class Biology Important Questions Chapter 6 Biodiversity and its Conservation

AP State Syllabus 8th Class Biology Important Questions 6th Lesson Biodiversity and its Conservation

8th Class Biology 6th Lesson Biodiversity and its Conservation 1 Mark Important Questions and Answers

Question 1.
What are Biosphere Reserves?
Answer:
Forests are Biosphere Reserves.

Question 2.
What is biodiversity?
Answer:
The variety and variability seen in plants and animals is called Biodiversity.

Question 3.
What are Endemic species?
Answer:
The plant or animal species of a particular area (zone), region or country is called endemic species.

Question 4.
What do you understand by Extinct?
Answer:
Species of plants and animals that have vanished from earth forever are called Extinct.

Question 5.
What do you understand the word Endangered?
Answer:
Plants and animal species that are on the verge of becoming extinct are called Endangered.

Question 6.
What is a Red Data Book?
Answer:
The book published by IUWC that contains the details of Endangered and Extinct species is called Red Data Book.

Question 7.
What do you see in National Parks?
Answer:
Conservation of wild life along with environment is seen in National Parks.

Question 8.
What is a sanctuary?
Answer:
A sanctuary is a place where conservation of wild life mostly birds takes place.

Question 9.
Give an example of a sanctuary.
Answer:
Krishna Sanctuary, Krishna & Guntur.

Question 10.
What is migration?
Answer:
Movement of birds for nestling from one region to another region is called migration.

Question 11.
Name the society for conservation of nature in London.
Answer:
International Union for Conservation of Nature and the Zoological Society of London.

Question 12.
Name the most threatened bird found in Palanadu Bird Sanctuary.
Answer:
Great Indian Bustard found in Pallanadu Bird Sanctuary.

Question 13.
Before 60 – 70 years what was the situation of the forests ofRampachodavaram?
Answer:
It was an abode for wild animals like tigers, leopards, deers etc.

Question 14.
What is the present situation of the forests ofRampachodavaram?
Answer:
Forest area was cleared and so several organisms started disappearing.

Question 15.
Why should we conserve a small insect like a bee or a butterfly?
Answer:
Most of the flowers get pollinated through bees and butterflies. So they should be conserved.

Question 16.
Why is the number of butterflies decreasing?
Answer:
The insects are decreasing due to spraying of pesticides and insecticides on crop plants.

Question 17.
How can ‘project tiger’ help to save wild life?
Answer:
This project helped to increase the number of tigers and to save tiger from the brink of extinction.

Question 18.
How is the project tiger achieved?
Answer:
The success of the project was achieved by enforcement of strict anti poaching measures and scientific conservation practices.

Question 19.
While saving tiger, why should it’s food web also be protected?
Answer:
The tiger depends for food on the deer and many other herbivores. If the tiger disappears, the deer and other herbivores will increase and that would affect the flora of the area.

8th Class Biology 6th Lesson Biodiversity and its Conservation 2 Marks Important Questions and Answers

Question 1.
What are the conservation methods do you suggest to protect the most threatened species?
Answer:

1. Taking measures to protect their natural habitats.
2. Creating awareness at community levels.
3. Strict implementation of National Wild life Protection Act, would help these species.
4. Prohibition of human activities in their habitats.

Question 2.
What are endemic species? Give some examples.
Answer:
Plants or animal species found restricted to a particular area of a country are called Endemic Species.
Ex: Broad tailed Grass bird, Peacock, Malabar Parakeet, Black Buck etc.

8th Class Biology 6th Lesson Biodiversity and its Conservation 4 Marks Important Questions and Answers

Question 1.
Collect the pictures of the following endangered species of plants and animals and paste them in your scrap book and write their names below the pictures.
Answer:

Question 2.
How do we depend on forests?
Answer:

1. Forests play a key role in maintenance of ecological balance.
2. Forests absorbs a large amount of Carbondioxide and Particulate Matter (CPM) and keep the air clean. They serve as lungs of our earth.
3. Forests are the natural sources of a variety of timber yielding plants and forests products like cane, resins, lac, fruits, nuts and honey.
4. Forests provide us with cool breeze which helps in the rainfall.
5. They are the natural habitats for wild animals they serve as biosphere reserves.

Question 3.
What steps do you take to stop deforestation?
Answer:

1. We should stop cutting of forests for farming and industrial purpose.
2. Planting trees like Tamarind, Amla, Tangedu, Subabul, Bamboo in rural areas.
3. Measures should be taken to conserve soil moisture by constructing checkdams and bundhs.
4. Measures should be taken to improve forest productivity by planting fruit and nut bearing plants.
5. Measures should be taken reforestation in order to maintain sustainability of forests.

8th Class Biology 6th Lesson Biodiversity and its Conservation Important Questions and Answers

Question 1.
List any four medicinal plants and their uses.
Answer:
The following are the some of the medicinal plants of our area and their use.

1. Neem – Antiseptic
2. Garlic – Used for lowering cholestrol and blood pressure.
3. Ginger – Used to ease nausea and motion sickness.
4. Feverfew – Used to treat fevers.

Question 2.
Match the following and answer the following question.
1) Endangered species              a) Hyderabad Pigeon
2) Endemic species                    b) Dinosaur
3) Invasive species                     c) Kiwi
4) Extinct species                       d) Spotted chital deer
e) Crow
Answer:
1 – d
2 – c
3 – a
4 – b
Question.
What is a Red Data Book?
Answer:
The book published by IUWC that contains the details of Endangered and Extinct species is called Red Data Book.

Question 3.
What is migration? Give some examples for migratory birds.
Answer:

1. Moving of birds in flocks from one region to another for getting shelter and food is called as “migration”.
2. Examples for migrating birds are great spotted wood pecker, coaltit, pelicon, black – tailed godwits, plover, etc.

Question 4.
Read the following paragraph.
Sometimes at night we see birds flying in groups. These birds which do not have permanent nestlings and join into small flocks and move from one region to other for food and shelter called as ‘Migration’ and such birds are called Migratory birds. During the rainy season most of the birds from far away places migrate to Kolleru and Pulicat lakes of our state. They build their nests on the trees in the nearby villages. Due to the cut down of trees, less number of birds are coming to here.
Answer the following questions.
a) What are Migratory birds ? Why do they migrate one place to another?
b) What are the reasons for less number of birds migrating to India?
Answer:
a) The birds which are moving in flocks from one region to other for food and shelter are called “migrating birds”.
b) Due to cutting down of trees in the villages near the lakes, birds are facing scarcity of their nesting habitats.

Question 5.
What measures are to be taken to save paper?
Answer:

1. We should always use recycled paper.
2. Use paper only if we need.
3. We should use electronic transfer methods for our daily transactions.
   Ex: Paying of electricity bills, filling of online application but not paper application.

Question 6.
Study the following para and answer the questions.
Did you get the same number and types of birds every day ? Was there any sudden variation in a particular season ? Did you notice any new type of bird population in any season ? Discuss with your friends about the effect of the presence of such a population. Why do these birds move from one place to another ? Sometimes at night we see birds flying in groups. Where do they fly? Think. Sometimes some birds live in the same habitat throughout the year. Other birds which don’t have permanent nestlings and join into small flocks and move from one region to the other for food and shelter (nesting habits) called as ‘Migration’ and such birds are called as ‘migratory birds ’. During rainy season most of the birds from far away places migrate to Kolleru and Pulicat lakes of our State. They build their nests on the trees in the nearby villages also. In the olden days people believed that these migrated birds are divine ones. But nowadays most of the trees are getting cut down. There is hardly any place for birds to build their nests.
a) What does the above information says?
b) What you say the birds come to our places from distant places?
c) What should we do for the birds to migrate to our place?
d) Name some migratory birds.
Answer:
a) Affects of deforestation on bird migration in Kolleru.
(Or)
Loss of bird habitats due to cutting down of trees in Kolleru.
b) Bird migration.
c) 1) Avoid cutting of trees in lake areas strictly.
2) We should strictly monitor the increased human activities in all lake areas.
d) Great spotted wood pecker, pelicans, coaltit, Siberian cranes.

Question 7.
What are the effects of deforestation?
Answer:

1. Change in rainfall pattern.
2. Increase in green house gases.
3. Loss of wild life habitats.
4. Increase in soil erosion.
5. Massive floods.
6. Global warming.
7. Droughts.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 2 Friction Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 2nd Lesson Friction

8th Class Physical Science 2nd Lesson Friction Textbook Questions and Answers

Improve Your Learning

Question 1.
Do you agree with the statement, “friction is both good and an evil”? Explain with examples.
Answer:
Yes, I agree with the statement friction is both good and an evil.
Explanation with examples.
a) Friction is good:

1. We cannot walk or run without friction.
2. We will not have any cars or bicycles because all of them move because of friction.
3. We cannot stop a moving car by applying brakes.
4. Carpenters will not be able to smoothen surfaces.
5. We will not able to hold any appliances such as hammer, soap, etc.
6. It will not possible to write with pen or pencil if there is no friction.
7. We could not fix nail on the wall.
8. No building could be constructed if there is no friction.

b) Friction is an evil: Friction is undesirable in machinery because it is responsible for overheating and wearing out of moving parts.

Question 2.
Explain why sportsmen use shoes with spikes.
Answer:
The spikes will increases the frictional force so that the sportsmen will get better grip on the floor.

Question 3.
Would it be easier or more difficult for you to walk on soapy water on the marble floor ? Why ?
Answer:
It is more difficult to walk on a marble floor having soapy water because soapy water acts as lubricant and decreases the friction.

Question 4.
What ways do you suggest to reduce friction?
Answer:
Ways of reducing friction:
a) Polishing: Decreasing irregularities of surface (or) smoothening the surface.
B) Lubricants: Using lubricants which will decrease the friction.
c) Ball bearings: Using ball bearings in machinery.
d) Steam lining: Automobiles and aeroplanes are steam lined to reduce the friction due to air.

Question 5.
What conditions are needed for static friction to come into play?
Answer:
The object should be at rest with respect to the surface upto certain limiting acceleration.

Question 6.
Give examples of practical application of static friction.
Answer:
The objects unable to move on their own is due to static friction between surfaces of object.
The practical application of static friction:

1. Construction of buildings.
2. Fixing nail in the wall.
3. A book placed in the shelf unable to change its position because it is unable to overcome frictional force.
4. We can write with pen or pencil due to static friction between finger and pen or pencil.
5. We will not able to hold appliances such as hammer.

Question 7.
Give examples showing the existence of sliding friction.
Answer:

1. A moving ball stops after sometime.
2. If we push an object it will stop after sometime.

Question 8.
Explain how can you measure frictional force?
Answer:
Tie a string around a brick. Pull the brick by a spring balance. When the brick just begins to move note down the reading on the spring balance that measure the force of friction between the surface of brick and the floor.

Question 9.
Explain how does lubrication reduce friction?
Answer:
When oil, grease or any other lubricants are applied between the moving parts of a machine, a thin layer formed between the moving surfaces so they do not directly rub against each other which will avoid the interlocking of irregularities. So lubrication reduce the friction.

Question 10.
What kinds of friction do you know?
Answer:
There are three types of friction.

1. Static friction
2. Sliding friction
3. Rolling friction

Question 11.
Explain why sliding friction is less than static friction.
Answer:
When an object starts sliding, the contact points on its surface do not get enough time to lock into the contact points on the floor. So the sliding friction is slightly less than the static friction.

Question 12.
Give examples of how is friction responsible for energy wastages? Give suggestions to reduce energy wastages by friction.
(OR)
How is friction responsible for energy loses give examples? Give suggestions to reduce energy loses by friction.
Answer:
As the friction increases the machinery parts develops heat there by efficiency of the machine decreases which leads lot of wastage of energy. The wastage of energy is due to overheating and wearing out of moving parts.
Suggestions:

1. To reduce friction between rotating shafts of machine tools we should have to use ball bearings.
2. Replacing wearing out of moving parts with new ones.

Question 13.
Seetha is observing a moving bus with the luggage on its top. As the bus is moving slowly there is change in the state of luggage on its top. But when the bus speeds up and starts moving fast, she noticed that the luggage on the top of the bus fell to the back of the bus. This raised many doubts in her mind regarding to the effect frictional force acting on the luggage as well as on the tyres of the bus. Can you guess the questions raised in her mind ? Write them.
Answer:

1. Why the bag is moving backward direction?
2. In which direction friction is acting on the bus as well as on the bag?
3. Whether frictional force effecting relative motion between bag and bus?
4. What happens to frictional force if we replace bag with other object?

Question 14.
Collect information either from internet or from books in library, about various new techniques being adopted by human beings to reduce energy losses due to friction. Prepare a note on that.
Answer:

1. We are using grease, oil, wax and other lubricants in the vehicles and machinery to reduce the friction.
2. Ball bearings are also used to reduce the friction.
3. Engine oil, gear oil, brake oil, clutch oil, etc. are used in vehicles.
4. Shock up oil is also used.
5. Levers are reducing the friction.
6. In trolleys and other vehicles which should carry heavy loads, the wheels are fixed.

Question 15.
Draw a free body diagram (FBD) to show various forces acting on a body which is sliding on an inclined plane.
Answer:

Question 16.
“Reducing friction to the lowest possible level in machine tools solves the problem of energy crisis and conserve biodiversity”. How do you support the statement? Explain.
Answer:
Yes, it will solve the problem of energy crisis and conserve biodiversity the reason is the majority of energy wasted in the form of heat energy due to friction. In order to develop more electrical energy we are depending on coal, petroleum, gas, nuclear energy and hydro electricity. The production of energy from these sources except hydroelectric power causing severe air pollution which are affecting animals and plants. So energy should be conserved by means of reducing friction.

8th Class Physical Science 2nd Lesson Friction InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 22

Question 1.
Does friction oppose motion or relative motion of surfaces in contact? Discuss.
Answer:
Yes. Frictional force opposition or relative motion of surfaces in contact that’s why an object placed on a table unable to move on its own because it is unable to overcome friction similarly a moving ball comes to rest after sometime due to friction.

Question 2.
What observations and experiments can you cite to show the existence of friction?
Answer:

1. Push a ball on a sandy surface and on a concrete surface and the observation is on a concrete surface it travels more distance, the reason is the concrete surface apply less frictional force on the ball.
2. Apply vehicle brakes during summer and rainy seasons and the observation is during summer season the brakes works more efficiently than rainy season the reason is friction between tyre and brakes is less because rainy water acts as lubricant.

Question 3.
When do we speak of sliding friction?
Answer:
When applied force is more than the limit of static friction, the body starts to move then we speak about sliding friction.

8th Class Physical Science Textbook Page No. 25

Question 4.
Does friction act on a table resting on the floor?
Answer:
Yes, frictional force is acting on the table which is known as static friction.

Question 5.
If normal force is doubled ? What happens to friction? Discuss.
Answer:
Friction is directly proportional to normal force therefore friction will be doubled if the normal force is doubled.

Question 6.
Your friend says “friction depends on the area of contact?” How do you correct your friend through some experiments ?
Answer:
If is plain that the friction doesn’t depend on area of contact, I will explain this fact to my friend by fastening a brick kept horizontal to the surface to a spring balance and pulling it at the hook. The same experiment I do by keeping the brick vertical to the surface. In both the experiments we find no difference and I will make him to come to the conclusion that the friction depends on the normal force and not on weight of the object on the surface of contact.

Question 7.
“Friction is independent of weight, but depends on normal force between surfaces of contact where friction exists.” Do you agree with this statement? Discuss.
Answer:
Yes, I agree with this statement. The above experiment helps us to come to this conclusion. In both cases we used the same brick hence the weight doesn’t change. But when its positions were changed the frictions at each case is changed.

8th Class Physical Science Textbook Page No. 26

Question 8.
What important role does friction play in the life of human beings and animals?
Answer:

1. Without friction human beings and animals unable to walk or run on any surface.
2. Without friction they unable to hold any appliances.
3. It will not be possible to write with pen or pencil if there is no friction.
4. We cannot stop car or cycle by applying brakes.
5. No building is constructed if there is no friction.
6. Carpenters will not be able to smoothen surfaces.

Question 9.
Why is friction important for transport?
Answer:
Threading in tyres provide friction for cars or buses so that they can move safely therefore friction is important for transport.

8th Class Physical Science Textbook Page No. 28

Question 10.
Can we reduce friction to zero? Explain.
Answer:
No, we cannot. Friction can never be entirely eliminated because no surface is perfectly smooth and some irregularities are always there.

Question 11.
What purposes are served by bearings in machines? Explain with daily life situations.
Answer:
The ball bearings are used to reduce friction between rotating shafts of machine tools and it increases the efficiency of machines.

8th Class Physical Science 2nd Lesson Friction Activities

Activity – 1
Question 1.
Identifying forces acting on a body and effect of frictional force.
Gently push a book on a horizontal floor. You may observe that the book acquires certain speed in the direction of push. However, the speed of the book gradually decreases and after sometime it stops.

a) Why does the book stop after covering some distance?
Answer:
Some opposing force is acting to its motion.

b) Is the book moving with uniform speed?
Answer:
No, its speed decreases gradually.

c) Why does the speed of the book change gradually?
Answer:
Some net force is acting opposite direction to its motion.

d) How many forces act on the book when it is pushed on the floor?
Answer:
Two forces act on the vertical direction. They are

1. Weight of the book or gravitational force acting vertically down.
2. Normal force or reaction force applied by the floor vertically up.
3. Forces acting horizontal direction.

e) What are the forces acting on the book in the horizontal direction?
Answer:

1. Muscular force applied by us.
2. Opposing force acting opposite to motion of book.

f) What is the net force acting in the horizontal direction?
Answer:
The net force is the difference between muscular force and opposing force to the motion of book.

Lab Activity

Write an activity to understand friction and static friction.
(OR)
Conduct an experiment to understand the nature of friction and the concept of static friction.
Answer:
Aim: To understand the nature of friction and the concept of static friction.
Materials required: Toy trolley, small wooden block, inextensible string, weight hanger, weights, pulley and table.
Procedure: Take a small toy trolley and keep a small wooden block on it as in the figure. Tie an inextensible string to the trolley and pass it over a pulley. And other end of the string is fixed to weight hanger. Take a small weight and keep it on weight hanger and observe the changes in motions of block and trolley.

Observation:
The trolley with block moves towards left with an acceleration. The block is not with respect to the surface of trolley, but it is in motion with respect to surface e table. The force of friction of the trolley acts on the direction of motion.
We increase trolley’s acceleration gradually by increasing the weight on the hanger at certain limiting weight the block comes in motion in the reverse direction.
That means now there exists relative motion between the surface of the trolley and block.
Result:
The force which opposes the relative motion of the two surfaces of bodies which are in contact is called frictional force.
The block is at rest relative to surface of the trolley upto a certain limiting acceleration. The friction exists at that stage is called static friction.

Activity – 2

Question 2.
Observing the variation of friction.
Push a heavy box which is kept on a floor. The box does not move. Now increase the applied force until the box moves.

a) Why does the box does not move at first?
Answer:
The applied force is less than frictional force (static friction).

b) When does the box tends to move?
Answer:
When the applied force is more than static friction.

Activity – 3

Question 3.
Effect of roughness on frictional force.
Set up an inclined plane on the horizontal floor. Use a wooden board as inclined plane. Put a mark at any point
‘A’. Now let a pencil cell or ball is move down from this point. Note down the distance travelled by the ball from the bottom of the inclined plane to point where it comes to a stop.

Now, spread a cloth over the floor. Try again with ball and note down the distance.

a) What are your observations from these experiments?
Answer:
The distance covered by ball in the two cases are different.

b) In which case is the distance covered maximum?
Answer:
When there is no cloth on the floor.

c) In which case is the distance covered minimum?
Answer:
When cloth is spread over the floor.

d) Why is the distance covered by the pencil cell different on different surfaces?
Answer:
Because, the friction offered by different surfaces are different.

e) If the cloth is replaced with white marble surface or glass surface, what will be your prediction about the distance covered by the pencil cell?
Answer:
The pencil cell covers more distance.

Activity – 4

Question 4.
Effect of area of contact on frictional force.
Tie a string around a wooden block and pull the wooden block by using a spring balance.

Pull it to make a move in the brick. Note down the readings of spring balance when the brick just begins to move.
a) How many forces are acting on the wooden block in the horizontal direction?
Answer:
Two forces are acting in the horizontal direction.

1. Force of friction,
2. Force applied by us.

Now turn the wooden block upright and measure the friction by doing the same experiment using the reading of the spring balance.

b) How does the frictional force vary with the change in the area of contact?
Answer:

The frictional force appears the same in both cases irrespective of area of contact. So it is independent of area of contact.

Activity – 5

Question 5.
Effect of normal force on friction.
Keep a wooden block on the horizontal floor and pull it with the spring balance attached to it and measure the frictional force.
Now put another wooden block over the brick tied to the spring balance or press it vertically with your hand and measure the frictional force.
a) Is there any difference between frictional forces in two cases? If yes, why?
Answer:
Yes, the reason is when we add a wooden block to the existing wooden block or apply force by pressing vertically, the normal force increases and hence we find increase in frictional force.

b) What is the relationship between friction and normal force?
Answer:
Friction is proportional to the normal force, i.e., friction °c normal force.

Activity – 6

Question 6.
Friction produces heat.
a) Rub your palms against each other for a few minutes. How do you feel?
Answer:

They became hot.

b) Strike a match stick against the rough surface of match box. What happens?
Answer:
The match stick catches fire.

c) What is your observation in this activity?
Answer:
Temperature of surfaces increases due to friction.

d) What is your conclusion on this activity?
Answer:
Friction can also produce heat.

e) You have probably heard that space craft returning to the earth have to be protected by a heat shield covering it. Find out why. What is the material used as heat shield?
Answer:

Space craft returning earth have to be protected by a heat shield covering it in order to protect it from atmospheric friction.
The material generally used is insulator of heat.

Activity – 7

Question 7.
How to increase Motion?
Take a spoon and hold its head (broader portion) in the left hand and hold the mid portion of the spoon by the right hand and pull it towards the other end of the spoon.
a) What do you notice?
Answer:
We unable to pull the spoon.
Now dip your right hand fingers in water, do it again as said above.

b) In which case is it easy to pull? Why?
Answer:
In second case it is easy to pull because water decreases the friction.

c) Have you ever thought why the sole of your shoes is grooved as shown in figure?
Answer:

It will provide shoes better grip on the floor so that we can move safely.

d) Cars, trucks and bulldozers tyres are threaded. Why?
Answer:

To provide them better grip on the floor.

e) Why do you need to change the tyres when it’s threading is worn out?
Answer:
If we does not change the tyre then the frictional force decreases and the vehicle may skid.
Play carrom board without powder and then play with fine powder sprinkled on board.

f) In which case is the movement of the striker and the coins easy? Why?
Answer:
When fine powder sprinkled on board, it will decrease the friction between coin and board surface.

g) Why do we pour a few drops of oil on the hinges of a door?
Answer:
It will decrease the friction and provide better movement of door.

h) Why do we use grease between the moving parts of motor vehicles?
Answer:
To reduce friction in order to increase efficiency.

Activity – 8

Question 8.
Effect of rollers on friction.
Pull a suitcase without rollers and pull a suitcase which has rollers.

a) In which case is the pulling easy? Why?
Answer:
It is easy to pull when suitcase has rollers.
Try to push a book lying on the table. Now place the book on two to three pencils or pens without caps. Push the book again.

b) What do you notice ? In which case is it easy to pull the book? Why?
Answer:

In the second case it is easy to pull the book. The reason is it is always easier to roll a body than to slide it over a surface.

Activity – 9

Question 9.
Understanding the principle of ball bearings.
Take two lids and rotate them by putting one on the top of the other.

a) What do you observe?
Answer:
It is difficult to rotate them.
Now place three to four marbles on one lid and place the other lid on the top of the marble. Now try to rotate the top lid.

b) What do you observe?
Answer:
Now we can easily rotate the lid because rolling friction is less than sliding friction.

c) What is your conclusion on the principle of ball bearings?
Answer:
We can easily rotate top lid by placing marbles between the lids. This is the principle of ball bearings.

Activity – 10

Question 10.
Observing fluid friction.
Take a glass of water and stir it with a spoon. You know that water whirls around an axis. Stop stirring and see what happens.

The whirling speed of water gradually decreases and after some – time, the water stops whirling and comes to a stable state

a) Which force is responsible for stopping the rotation of the water.
Answer:
The frictional forces between the liquid layers or between the liquid surfaces that is in contact with glass surface.

Activity – 11

Question 11.
Identifying factors influencing the fluid friction.
Take a tub of water. Try to move your hand in water in the direction of stretched fingers i.e., up and down. Now try to move your hand in the direction perpendicular to the plane of the hand i.e., to and fro.

a) In which orientation of your hand, do you experience more drag? Why?
Answer:
We experience more drag in the direction of stretched fingers. The frictional force on an object in a fluid depends on its speed with respect to fluid and on the shape of the object and nature of the fluid.
When objects move through fluids, they have to overcome friction acting on them. So objects are given special shapes to minimise fluid friction.

b) Where do you think scientists get hint for these special shapes?
Answer:
From nature i.e., from birds and fishes, which have to move about in fluids all the time.

c) Do you find any similarity in the shape of an aeroplane and a bird? Why?
Answer:
Yes. The shape of aeroplane designed as bird in order to reduce fluid friction.

AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 3 Matter Around Us

AP State Syllabus 8th Class Physical Science Important Questions 3rd Lesson Matter Around Us

8th Class Physical Science 3rd Lesson Matter Around Us 1 Mark Important Questions and Answers

Question 1.
What is CNG?
Answer:
CNG means Compressed Natural Gas.

Question 2.
Does the smoke of incense stick diffuse in a room without air?
Answer:
Smoke of incense stick is a gas. Gas diffuses in air only. So the smoke cannot diffuse in the absense of air.

Question 3.
Write decreasing order of the distance between the atoms of solid, liquid and gas.
Answer:
Gas > Liquid > Solid.

Question 4.
What is the temperature where water expands?
Answer:
When temperature is reduced from 4°C to 0°C, water expands instead of compression.

Question 5.
What is dry ice?
Answer:
Solid carbon dioxide is called dry ice.

Question 6.
What is Kelvin scale equivalent to 0°C?
Answer:
273 K.

Question 7.
What are the factors influencing the change in state of a matter?
Answer:

1. Temperature
2. Pressure.

Question 8.
What is humidity?
Answer:
The amount of water vapour present in air is known as humidity.

Question 9.
What is meant by sublimation?
Answer:
When a substance is heated its state changes from solid to vapour directly without changing into liquid. This is called sublimation.

Question 10.
How do acquatic animals and plants survive under water?
Answer:
The gases like oxygen and carbon dioxide will diffuse in water. The acquatic animals under water will survive by inhaling these gases.

Question 11.
What are the different states of matter?
Answer:
Matter exists in three states. They are solids, liquids and gases.

Question 12.
Why are the liquids called fluids?
Answer: Liquids can flow easily from one container to another. Hence they are called fluids.

Question 13.
Why is the solid carbon dioxide called dry ice?
Answer:

1. Solid carbon dioxide converts directly into gaseous state when the pressure is decreased to 1 atmosphere.
2. Due to this reason solid carbon dioxide is also known as dry ice.

Question 14.
Why is the rate of diffusion in gases high?
Answer:
The rate of diffusion in gases is very high than liquids and gases, because

1. Higher speed of gas particles.
2. Greater space between the particles of gas.

Question 15.
Which will decide the change of state of substance?
Answer:
Pressure and temperature decides the state of the substance.

Question 16.
What is the principle involved in ice skating?
Answer:
Pressure is applied on ice with skating boots. As the pressure increases melting point ice decreases. So ice melts at a lower temperature than 0°C. Therefore skating is possible on ice.

Question 17.
What is compression?
Answer:
The volume of gas can be decreased by applying pressure. This process is called compression.

Question 18.
What are fluids?
Answer:
The substances which can flow from one place to other place are called fluids. Generally liquids and gases are fluids.

8th Class Physical Science 3rd Lesson Matter Around Us 2 Marks Important Questions and Answers

Question 1.
What is matter? Give some examples from your day-to-day life.
Answer:
Anything in this world that occupies space and has mass is considered as matter. Examples:
The water we drink, our food, clothes, chairs, tables, air we breath, etc. are the examples of matter.

Question 2.
Compare the following properties of solids, liquids and gases,
a) Shape b) Volume c) Compressibility d) diffusion
Answer:

Question 3.
Give the order of rate of diffusion in solids, liquids and gases.
Answer:
The order of rate of diffusion in solids, liquids and gases is
Gases > Liquids > Solids (or) Solids < Liquids < Gases

Question 4.
Give some experiences with evaporation in your daily life.
Answer:

1. We feel cooler after sweating.
2. Drying of wet clothes when exposed to the sun.
3. Paddy, cereals, etc. will be exposed to the sun to remove moist.
4. Water stored in earthen pots is cooler than the water stored in a metal pot.
5. Fog, which is formed early in the morning during winter season will disappear after sunrise.

Question 5.
Why do we feel cool when nail polish is applied to nails?
Answer:
Nail polish contains acetone which absorb heat energy from our body and evaporates. So the body temperature decreases. So we feel cool when nail polish applied to nails.

Question 6.
Why do we store water in earthen pots?
Answer:
The earthen pots have small pores in it. From that pores water tends to evaporates by gaining heat energy from the pot. So water in pots is cool. So water is stored in earthen pots.

Question 7.
Why do clothes dry faster on a sunny and windy day compared to rainy season ?
Answer:
If the amount of water vapour is high in air the rate of evaporation will decrease. So clothes dry slowly during rainy season but fast on a sunny and windy day.

Question 8.
Why do we require pressure cookers at higher altitudes?
Answer:
At higher altitudes the atmospheric pressure decreases. So the boiling point of water decreases. So, the heat energy supplied is not sufficient to cook food. Therefore we require a pressure cooker to increase the pressure. Thus the boiling point of water inside the cooker increases to 120°C and heat energy is sufficient to cook food.

Question 9.
Two pieces of cotton rolls one is soaked in ‘A’ chemical, and other one is soaked in ‘B’ chemical are inserted in a glass tube as shown in the figure.

a) If ‘A’ is HCl, what would be ‘B’?
b) In which state the rate of diffusion is high?
Answer:
a) If ‘A’ is HCl, then ‘B’ should be Ammonium solution. Because it formed Ammonium chloride.
b) Rate of diffusion is high to ‘B’ than ‘A’.
Because the product Ammonium chloride formed nearer to ‘A’ chemical.

Question 10.
One part of the substance was boiled in water at 100°C. Other part of the substance was boiled in water vapour at 100°C.
a) Which one would be boiled fast?
b) Guess the reason.
Answer:
a) Substance boiled in water vapour at 100°C is boiled fast.
b) Particles in water vapour at 100°C have more energy than the particles in liquid water at the same temperature. This is because of particles in water vapour have absorbed additional energy in the form of heat of vaporization.

Question 11.
Balaraju hanged his washed clothes under fan which is rotating.
Venu Gopal hanged his washed clothes under shadow.
a) Which one dries early? Why?
b) Write the name of the process that involved in drying.
Answer:
a) The clothes hanged by the Balaraju were dried faster, because, evaporation increases with wind speed.
Due to increase of wind speed, water vapour particles move away with the wind, decreasing the amount of water vapour in the surroundings.
b) The process involved in drying up the clothes is evaporation.

Question 12.
Observe the given graph and answer the following :

1. What is the melting point in the graph?
2. What is the boiling point in the graph?
3. Guess the substance.
4. What is the maximum temperature that hold the substance?

Answer:

1. The melting point is 0°C.
2. The boiling point is 100°C.
3. The substance should be water.
4. We can rise the temperature of the substance upto 100°C.
   The maximum temperature that hold by the water is 100°C.

8th Class Physical Science 3rd Lesson Matter Around Us 4 Marks Important Questions and Answers

Question 1.
How can you prove that the solids have definite shape and a fixed volume ?
Answer:

1. Take two solid objects, say a pen and a book.
2. Put them in different containers.
3. We observe that there is no change in their shape or volume.
4. Drop a book on the floor.
5. If will not flow like a liquid, but remain rigid.
6. These activities prove that solids have definite shape and a fixed volume.

Question 2.
What are the general properties of matter ?
Answer:
The general properties of matter:

1. Matter is made up of tiny particles. Their size is beyond our imagination.
2. Matter exists in three states i.e. solid, liquid and gas.
3. There exists space between the particles of matter.
4. There exists some force of attraction between the particles of matter.
5. Matter can change its state from solid to liquid, liquid to gas and vice versa, by changing temperature and pressure.
6. Matter has the properties of compressibility and diffusion.
7. Particles of matter move continuously in liquids and gases.

Question 3.
Define: a) Latent heat b) Latent heat of fusion c) Latent heat of vaporisation.
Answer:
a) Latent heat: The amount of heat energy that is required to overcome the attraction
energy among the particles is given by the latent heat of the substance.
b) Latent heat of fusion: Latent heat of fusion is defined as the amount of heat energy required to change 1 kg of a solid, completely into liquid at atmospheric pressure at its melting point.
c) Latent heat of vaporisation : Latent heat of vaporisation is defined as the amount of heat energy required to change 1 / of a liquid, completely into vapour at atmospheric pressure at its boiling point.

Question 4.
How is marine life possible in extremely cold areas ?
Answer:

1. The volume of water between 0°C to 4°C shrinks.
2. Same amount of water in solid ice occupies more volume than liquid water.
3. So ice floats on water rather than shrinking.
4. In extremely cold weather, the water at the top becomes colder and colder, until it freezes.
5. While the ice floats on the top, the animals continue to live in the water below, which does not freeze and remains at 4°C.
6. The ice on the top of the pond insulates the water, below it as it stops the water from losing the heat to air.
7. This is very important for survival of marine life which lives in ponds in the colder areas.

Question 5.
How does diffusion helps to survive the animals and plants in daily life ?
Answer:

1. It is clear that solids and liquids diffuses into liquids and gases diffuses into gases.
2. Certain gases from atmosphere particularly oxygen and carbon dioxide diffuse and dissolve in water and support the survival of aquatic animals and plants.
3. Diffusion therefore is a very important process for living things.
4. During respiration oxygen diffuses from lungs into blood. Carbon dioxide diffuses from blood into lungs.

Question 6.
How do you appreciate the process of diffusion ?
Answer:

1. Diffusion is a very important process for living things.
2. Oxygen diffuses into air and available for every human beings and animals.
3. CO₂ diffuses into air and available to plants.
4. Oxygen and CO₂ diffuse and disolve in water and support the survival of aquatic animals and plants.
5. During respiration oxygen diffuses from lungs into blood.
6. Smell of flowers, scents diffuses and reaches to our nose to give happiness to us.
7. We can recognise leaking of L.P. Gas in our house by diffusion process.
8. Diffusion of sugar and salt, give taste to drinks.
9. In this way diffusion is useful in our daily life.
   So, I am appreciating the process of diffusion.

Question 7.
How do you appreciate the process of evaporation ?
Answer:

1. The process of change of a liquid into vapours at any temperature below its boiling point is called “evaporation”.
2. It is very useful in our daily life.
3. Drying of wet clothes in air is the result of evaporation.
4. Drying of sweat from the human body and giving cooling is also result of evaporation.
5. After washing the floors, dishes evaporation takes place and dries up.
6. Water cools when it store in matkas (earthen pots). Evaporation process involved in it.
7. Water evaporate from the sea and forms clouds to rain.
8. In this way evaporation process is helpful to us.
9. So, I am appreciating it.

Question 8.
Find out the process involved in given situations.

Answer:
a) evaporation
b) melting
c) evaporation
d) diffusion
e) diffusion
f) boiling
g) diffusion
h) evaporation

AP State Syllabus AP Board 8th Class Physical Science Important Questions Chapter 7 Coal and Petroleum

AP State Syllabus 8th Class Physical Science Important Questions 7th Lesson Coal and Petroleum

8th Class Physical Science 7th Lesson Coal and Petroleum 1 Mark Important Questions and Answers

Question 1.
What are exhaustible resources? Give examples.
Answer:
The resources which are limited in nature and can be exhausted by human activities are called exhaustible resources, e.g. Coal, petroleum and natural gas.

Question 2.
What are inexhaustible resources? Give examples.
Answer:
The resources which are unlimited in nature and not likely to be exhausted by human activities are called inexhaustible resources, e.g. Solar energy, wind energy, tidal energy.

Question 3.
When and where does petroleum first used?
Answer:
More than 4000 years ago, asphalt (petroleum product) was used in the construction of walls and towers of Babylon. There are also records from ancient China about shallow wells being dug to get petroleum.

Question 4.
What did our ancestors do with petroleum?
Answer:
They mainly used petroleum for their wooden boats and waterproof, as a fuel for lamps and in some traditional remedies.

Question 5.
What is the basic difference between coal and charcoal?
Answer:
Coal used in factories is mined from the earth’s crust. The charcoal is obtained from firewood.

Question 6.
What is meant by fractional distillation?
Answer:
The separation technique used to separate various components of petroleum is called fractional distillation.

Question 7.
What is carbonisation?
Answer:
The slow process of conversion of dead vegetation into coal is called carbonisation.

Question 8.
Why coal, petroleum and natural gas are called fossil fuels?
Answer:
They were formed from the dead remains of living organisms (fossils). So these are called fossil fuels.

Question 9.
What is coke and what are its uses?
Answer:
Coke is a tough, porous and black substance. It is an almost pure form of carbon. Uses:

1. Coke is used in the manufacture of steel.
2. In the extraction of many metals.

Question 10.
Why petroleum is called black gold?
Answer:
Due to its great commercial importance petroleum Is called black gold.

Question 11.
What are alternatives to natural gas? Why do not we are using them?
Answer:
The alternatives for natural gas are coal bed methane and gas hydrates. These are not in commercial production phase due to lack in proper technology.

Question 12.
Can coal, petroleum and natural gas be prepared in the laboratory from dead organisms?
Answer:
No, their formation is very slow process and conditions for their formation cannot be created in the laboratory.

8th Class Physical Science 7th Lesson Coal and Petroleum 2 Marks Important Questions and Answers

Question 1.
How do you obtain various materials we are using in our daily life?
Answer:

Question 2.
What is biodiesel? How would you prepare biodiesel? What is its use?
Answer:
Biodiesel is one of the biofuel. Which is not toxic and renewable. It is made from the biological ingredients instead of petroleum or crude oil. Biodiesel usually made from the plant oils or animal fat through a series of chemical reactions.
It is used in diesel engines.

Question 3.
What is coal? Explain the process of formation of coal.
Answer:
Coal is hard and black coloured substance obtained from mines.

The plants in large and dense forests in low lying wet lands got buried under the soil due to natural processes like floods and earthquakes. As more soil deposited over them, the organic matter was compressed. The temperature also rose. As the organic matter sank deeper and deeper, under high temperature and high pressure, the dead plants slowly converted to coal.

Question 4.
What is coal tar and what are its uses?
Answer:
Coal tar: It is a black coloured thick liquid with an unpleasant smell. It is a mixture of about 200 substances.
Uses:
Products obtained from the coal tar are used as starting material for various substances like synthetic dyes, drugs, explosives, perfumes, plastics, paints and roofing material. Naphthaleine balls obtained from coal tar used to repel moths and other insects.

Question 5.
What is coal gas and what are its uses?
Answer:
Coal gas is a gas obtained during the processing of coal to get coke.
Uses:

1. It is used in lighting.
2. It is used as fuel in many industries.

Question 6.
What are petrochemicals? What are the uses of petrochemicals?
Answer: The useful substances which are obtained from petroleum and natural gas are called petrochemicals.
Uses:
They are used in the manufacture of detergents, synthetic fibres (polyester, nylon, acrylic) polythene, etc.

Question 7.
Draw a table showing uses of petrochemicals in various sectors.
Answer:

Question 8.
Why are coal and petroleum so versatile?
Answer:
Coal consists of mainly carbon while petroleum consists of mixture of compounds called hydrocarbons. These compounds make good starting materials for other compounds based on carbon. Carbon is very versatile and is basis for most of the materials.

Question 9.
Why does the price of petrol go up all the time?
Answer:
The price of anything depends on how much of it is available and how essential it is. Both coal and petroleum are exhaustible resources but we need them, both as fuel and as starting material for synthesising new compounds. Since supply is limited and becoming more expensive as the demand for petrol increase.

Question 10.
What is natural gas ? What are the advantages of CNG as fuel?
Answer: Natural gas is a very important fossil fuel.
CNG: Natural gas is stored under high pressure as compressed natural gas. Advantages of CNG as fuel:

1. CNG is less polluting and it is a cleaner fuel.
2. The great advantage of CNG is that it can be used directly for burning in homes and factories where it can be supplied through pipes because CNG travels large distances.

Question 11.
Ramu told Rahim that solar energy is inexhaustible resource then what are the questions raised in the mind of Rahim about solar energy?
Answer:

1. If it is inexhaustible resource of energy why don’t we are using it?
2. Whether utilization of solar energy is difficult?
3. Whether sophasticated techniques not available for proper use of solar energy at present?
4. It is costly to use solar energy for producing electric power?

Question 12.
Explain why petroleum is also called as liquid gold.
Answer:

1. They are many useful substances are obtained from petroleum which are called petrochemicals.
2. These are used in the manufacture of detergents, synthetic fibres such as polyester, nylon, acrylic, polythene, etc.
3. Due to great commercial importance petroleum is also called liquid gold.

Question 13.
What will happen if fossil fuels like coal and petroleum are completely exhausted?
Answer:

1. Coal and petroleum are the natural resources which are important resources of energy for us.
2. Coal is used as a fuel as such in homes and in industry, or it is used to generate electricity at thermal power plants.
3. Petroleum products such as petrol and diesel are used as fuels in transport to run scooters, motorcycles, cars, buses, trucks, trains and aeroplanes.
4. Kerosene and LPG obtained from petroleum are used as domestic fuels for cooking food.
5. Since the industrial revolution, we have been using increasing amount of energy. So we need more energy resource.
   So without coal and petroleum products life on the earth is impossible.

Question 14.
Suggest some alternative ways to save the fuel resources. (Or)
What actions are required to meet the future energy needs?
Answer:

1. Do not waste fuel for unnecessary activities.
2. The energy should be properly utilized and the wastage should be minimized.
3. Usage of bicycle in place of motor vehicles for small distances.
4. Using road transport vehicles for travelling larger distances which will minimize fuel consumption.
5. The engine of a vehicle thoroughly serviced in order to minimize fuel consumption.
6. Alternative sources like solar energy, wind energy, tidal energy are more utilized.

Question 15.
Burning fuels releases carbon dioxide , a green house gas, which causes climate changes and leads to global warming. Collect information about this through newspapers, magazines, etc. and prepare report.
Answer:
i) Drastic increase in the emission of CO₂ within last 30 years caused by burning of fossil fuels has been identified as the major reason for the change of temperature in atmosphere.
ii) Carbon dioxide in the atmosphere traps the reflect sunlight and re-emitt towards earth which is causing increase of earth temperature what we call as global warming.

Question 16.
Describe characteristics and uses of coke.
Answer:

1. It is tough, porous and black substance.
2. It is almost pure form of carbon.
3. Coke is obtained by heating soft coal in the absence or little supply of air.
4. It is used in the manufacture of steel and extraction of many metals.

8th Class Physical Science 7th Lesson Coal and Petroleum 4 Marks Important Questions and Answers

Question 1.
Is petroleum exhaustible? Explain.
Answer:

1. If we see the history of petroleum production, from 1859 to 1969, the total production of oil was 227 billion barrels.
2. 50% of this total was produced during the first 100 years, while the next 50% was extracted in just ten years.
3. Today our consumption rate of oil is far excess that of the rate of its formation.
4. Earth take more than one thousand years to form the oil that we consume in one day.
5. By about 2015, we would have consumed half of the total reserves of the oil.
6. It would become more and more difficult to extract oil in future.
   So petroleum is exhaustible.

Question 2.
Draw a diagram showing existence of various fuels like natural gas, petroleum in earth crust.
Answer:

Question 3.
Collect information about places where we get coal, petroleum and natural gas in India and mark the places on outline map of India.
Answer:
Coal: Jharia, Chandrapura, Bokaro, Giridih (Jarkhand), Ranigunj and Asansol (West Bengal), Singrauli (M.P.), Korba (Chhattisgarh), Singareni (A.P.) : Talcher and Rampur Himgir (Odisa) and Chand coal field (Maharashtra).
Petroleum : Digboi, Hugrijan, Moran, Naharkatiya, Sibsagar, Rudrasagar and Badarpur (Asom), Bombay High (Maharashtra), Ankleshwar, Kosamba, Kalol, Mehsana, Navagam and Dholka (Gujarat), Krishna and Godavari river basins (A.P.)
Natural gas: Cambay and Ankleshwar fields (Gujarat) and Bombay High (Maharashtra), Coastal Andhra Pradesh.

8th Class Physical Science 7th Lesson Coal and Petroleum Important Questions and Answers

Question 1.
Write any two uses of petrochemicals in our daily life.
Answer:
Uses: They are used in the manufacture of detergents, synthetic fibres (polyester, nylon, acrylic) polythene, etc.

Question 2.
It is necessary to save the energy resources like petroleum and natural gas. Write a slogan about this to create awareness among people.
Answer:

1. ‘Save petrol and save future’.
2. ‘Save fuel and save earth’.

Question 3.
Petroleum is a complex mixture. Write the technique to separate its components.
Answer:
The technique to separate petroleum components is ‘fractional distillation’.

Question 4.
Write any two uses of Activated Carbon in our daily life.
Answer:
Uses of Activated Carbon:

1. Activated Carbon is used to purify liquids.
2. It is used to treat many types of oral poisonings.

Question 5.
Assume that you are a driver, what measures do you take to save petrol?
Answer:
Engine must be stopped in the traffic signals or in heavy traffic.

Question 6.
The following table shows the total power shortage percentage in India from 1994-1997. Observe the data and give the answers to the following questions.
i. In which year the shortage percentage of power is least?
ii. Between which two years the shortage percentage difference is more?
iii. In which year the shortage percentage of power is maximum?
iv. Make a comment on shortage percentage of power between 1994-95.
Answer:
i. 1995
ii. Between 1996 and 1997
iii. 1997
iv. Shortage percentage is decreased by 0.3 in between 1994 – 95.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 5 Metals and Non-Metals Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 5th Lesson Metals and Non-Metals

8th Class Physical Science 5th Lesson Metals and Non-Metals Textbook Questions and Answers

Improve Your Learning

Question 1.
Explain the physical properties of metals with suitable examples.
(OR)
Explain briefly the physical properties of metals.
Answer:
Physical properties of metals:

1. Lustrous:
   When we rub the surface of metals with sand paper they will shine. This property is called lustrous, e.g.: Iron, zinc etc.
2. Sonority:
   When we hit the metal surface they give a ringing sound is called sonority, e.g.: Iron, copper etc.
3. Malleability:
   Metals can be flattened into thin sheets. The property of flattening metals into thin sheets is called malleability, e.g.: Silver, Iron, copper.
4. Ductility:
   Metals can be drawn into wires.
   The property of drawing a metal to make fine wire is called ductility, e.g.: Silver, gold.
5. Electric conductivity:
   Electricity can be easily pass through metals. So they are called good conductors of electricity.
   e.g.: Silver, copper, iron.
6. Conductivity of heat:
   Metal absorbs heat quite easily. They are good conductors of heat, e.g.: Copper, iron.

Question 2.
You are given two samples. How do you distinguish which is metal and which is non-metal?
Answer:

1. By physical properties, generally we can judge whether the given sample is metal or non-metal that is metals are hard. They are lustrous, sonorous, malleable, ductile and good conductors of heat and electricity.
2. Generally metal sample react with water and non-metal sample does not react with water.
3. Generally metal sample react with acid and produce hydrogen gas whereas non-metal samples does not react with acid.

Question 3.
Which metals are used in making jewellery? Why?
Answer:
Generally we use metals like gold, silver and copper for making jewellery due to their high ductility and lustrous surface.

Question 4.
Which substance liberate hydrogen when react with metals?
Answer:
Generally acids react with metals and liberate hydrogen gas. Water also react with some metals and liberate hydrogen gas.

Question 5.
In a chemical reaction iron is unable to displace zinc from zinc sulphate. Why?
Answer:
Zinc is more reactive than iron. A less reactive metal cannot displace a more reactive metal from its salt solution. So iron unable to displace zinc from zinc sulphate.

Question 6.
Why cooking pans do not have metal handles?
Answer:
Metals are good conductors of heat. So they gain heat easily. So in order to avoid the burning of our palms, the handles of cooking pans made of heat resist material such as plastic.

Question 7.
Sulphur dioxide is
A) basic oxide
B) acidic oxide
C) neutral oxide
D) amphoteric oxide
Answer:
B) acidic oxide

Question 8.
Match the following.
Group – A                                             Group – B
1. Making into thin sheets        ( )        A) Ductility
2. Shining materials                  ( )        B) Conductivity
3. Making into wires                 ( )        C) Sonority
4. Transmission of heat            ( )        D) Lustrous
5. Making ringing sound          ( )         E) Malleability
Answer:
1. E
2. D
3. A
4. B
5. C

Question 9.
Which gas makes a ‘pop’ sound if exposed to lighted matchstick?
Answer:
Hydrogen gas makes a pop sound when it is exposed to a lighted matchstick.

Question 10.
Why are bells made up of metals instead of wood
Answer:
Metals have sonority property that means they make ringing sound when we hit them with a hammer. Where wood does not give ringing sound when it is hit with a hammer. So bells are made up of metals instead of wood.

Question 11.
Imagine the human life without metals, write briefly about the consequences.
Answer:

1. There would not be any utensil for cooking.
2. There would not be trains, buses, aeroplanes for travelling.
3. There would be no almirahs, no school bells, no agricultural material, no electrical appliances, no automobiles, no satellites, no machinery and no decorative material. So everything in life directly or indirectly depends upon metals. So we cannot imagine a life without metals.

Question 12.
After completion of metals and non-metals chapter, Raheem understood that metals are hard and non-metals are soft. During the discussion with his brother he came to know that diamond is a hardest material and it is a non-metal. Similarly mercury is a soft material and it is a metal. These findings from the discussion raised some questions in Raheem’s mind. Can you guess those questions? Write them.
Answer:
The doubts arised in Raheem’s mind are

1. If diamond is hard how it behaves like a non-metal?
2. If mercury is soft material how it acts as metal?
3. What are the properties which actually decide whether the given material is either metal or non-metal?

Question 13.
Discuss the acidic and basic nature of the metals and non-metals with suitable experiments.
Answer:
Take a small strip of magnesium and burn it. It forms white ashes of magnesium oxide collect the ashes of magnesium and add some distilled water to it. Test the solution with red and blue litmus papers. Note the colour changes. The solution turns red litmus into blue. It indicates given solution is basic. So metallic oxides are basic in nature.
Take a small amount of powdered sulphur in a deflagrating spoon and heat it. As soon as sulphur starts burning, introduce the spoon into a gas jar or tumbler. Cover the tumbler with lid to ensure that the gas produced does not escape. The gas formed is sulphur dioxide. Remove the spoon after some time but try to keep the jar covered. Add a small quantity of water into the tumbler and quickly replace the lid. Shake the tumbler well. Check the solution with red and blue litmus paper. The solution turns blue litmus into red. It indicates the solution is acidic. So non-metallic oxides are acidic in nature.

Question 14.
How do you appreciate wide range utility of aluminium right from utensils to space craft?
Answer:
Aluminium is essential part of our life. Aluminium foil is used on inner packing of food materials and toffees. Aluminium and copper mixture is used in currency coins, medals and statues. Aluminium is used in electrical appliances, automobiles, satellites, space crafts, aeroplanes, cooking utensils, machinery, decorative materials. This indicates wherever we go we observe articles made up of aluminium. So we require aluminium for better living.

Question 15.
How is malleability of metals used in our daily life
Answer:
Metals can be flattened into sheets is called malleability. Due to this metals can be made into different shapes like railway coaches, railway tracks, cooking utensils, etc. So malleability of metals is extremely useful in daily life.

Question 16.
Dumping of waste material made up of metals and non-metals leads to environment pollution. Do you support the statement? Give your justification with suitable examples.
Answer:
Soil samples analyzed from location adjacent and with in deposite show high level of heavy metals in particular lead, mercury, cadmium, copper and chromium. In which lead and mercury are extremely harmful to environment as well as mankind. After medical evaluation the adolescents living and children living near dump site had high incidence of diseases that are associated with high exposure levels to these metal pollutants. So waste material made of metals and non-metals leads to environmental pollution. Some more examples are burning of sulphur forms sulphur dioxide and sulphur trioxide, which is a cause for acid rain and soil corrosion. In complete burning of carbon leads to release of poisonous carbon monoxide.

8th Class Physical Science 5th Lesson Metals and Non-Metals InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 68

Question 1.
How will you close the circuit using sulphur, carbon or iodine? They may be in powder form. Try to tightly pack the powder in a straw and use it. Think of other ways!
Answer:
Circuit will not be completed by using non-metals like sulphur, carbon or iodine because they are bad conductors of electricity. So by packing the powder will not complete the circuit. There is no other by using which we can complete the circuit by using a non-metal.

Try This

8th Class Physical Science Textbook Page No. 74

Question 1.
Recall the names of the some of the laboratory acids and bases that you know. Write down their names in table and identify metal/non-metal present in them, which form oxides when react with oxygen. Take the help of your teacher.
Answer:

Question 2.
Have you seen a periodic table?
Answer:
Yes.

Question 3.
Try to find the metals and non-metals that you come across in the chapter on the periodic table.
Answer:
Metals               Non-metals
1) Zinc               1) Sulphur
2) Copper          2) Chlorine
3) Iron               3) Nitrogen
4) Potassium     4) Carbon
5) Sodium         5) Phosphorus
6) Gold
7) Silver
8) Magnesium
9) Calcium
10) Aluminium

8th Class Physical Science 5th Lesson Metals and Non-Metals Activities

Activity – 1

Question 1.
Observing appearance and colour of some materials:
Observe the appearance of your samples. Look at their colour. Decide whether they appear shining or dull and record your observations in table. If the surface seems dirty, clean it with sand paper.

a) Which of the samples did not shine even after you cleaned them with sand paper?
Answer:
Sulphur, carbon.

b) Generally metals are lustrous. Do all lustrous materials are metals?
Answer:
No. Some may be non-metals, e.g.: Iodine

c) We all know that mirror is lustrous. Can a mirror be called metal?
Answer:
No. Several properties required to decide if a given material is metal or not.

Activity – 2

Question 2.
Listening the sound produced by some material:

a) Drop a piece of coal on the floor and listen the sound.
Do you think coal is sonorous?
Answer:
No.

b) Take the pieces of zinc, copper, aluminium, magnesium and tightly packed packets of sulphur, carbon and iodine. Drop them one by one, on a hard surface. Listen carefully to the sound produced and record your observation in table.
Answer:

c) What similarity do you notice among materials which produce sound?
Answer:
All of them are metals.

d) Which property of metals first attracted the attention of human beings?
Answer:
Metals had the advantage of not just being harder but they could be heated in a fire and moulded or cast into different shapes. This property of metals first attracted the attention of human beings.

e) Do you bring a similar change in the shape of a clay material by beating it?
Answer: Yes, we bring similar change in the shape of a clay material by beating it.

Activity – 3

Question 3.
Identifying malleability of material:
Take a hammer and beat the material samples which are used in Activity-2 and observe the changes in material samples. Record your observations in the table.
Answer:

Some of the samples like zinc, copper are flattened whereas some materials such as carbon, iodine broken into pieces.
The materials which can be flattened into thin sheets are called malleable materials.
Ductility:
We use wires in different situations in our daily life. Look at the samples given in the table.

a) Have you ever seen the wires made up of materials mentioned in the above table?
Answer:
Yes. I have seen the wires made of iron, copper, aluminium.

b) What is the property of drawing material to make wire is called?
Answer:
Ductility.

Activity – 4

Question 4.
Identifying electric conductivity of a material:
Arrange an electric circuit with a battery and bulb. Close the circuit using an iron nail, as shown in figure. Observe whether the bulb glows or not. Record your observations in table. Repeat the same experiment using the other samples and record your observations in the same table.

a) Do all the samples allow the bulb to glow?
Answer:
No. Materials like iron, zinc, copper allows bulb to glow.

b) What is name given to these material which allows electricity to pass them and make to bulb to glow are called?
Answer:
They are called conductors.

c) Give examples for good conductors of electricity?
Answer:
Copper, iron, aluminium

d) Talk to an electrician. Look at the handles of his tools. Are the handles made of the same materials? If not why?
Answer:
No. The handles of his tools are made of electrical insulating material in order to avoid electrical shock.

Activity – 5

Question 5.
Observing heat conduction by metals:

Take an iron rod. Stick pins on it with the help of wax. Now fix the rod to a stand as shown in figure. Heat one end of the rod with a spirit lamp and see how the pins fall off?

a) Why did the pins fall off from iron rod?
Answer:
Iron rod gains heat from spirit lamp.

b) Pin of which end fell off first?
Answer:
The pin which is near to spirit lamp falls first.

c) What could be the reason for this?
Answer:
The pin falls off because of heat supplied to the iron rod and makes the wax to melt at one end. The wax closer to the flame melted first and the pin falls off. Then the other pins falls. This activity shows that heat moves from one end of the rod to the other. This property of a material is known as conductivity of heat.

d) Go back to the list of samples. On the basis of all the activities carried out, fill the following table.
Answer:

Lab Activity

Conduct an experiment to know the reaction of oxygen with metals and non-metals.
Answer:
Aim: To know reaction of oxygen with metals and non-metals.
Materials required: One metal sample (Magnesium) and one non-metal sample (Sulphur), spirit lamp or Bunsen burner and litmus paper, etc.
Procedure:
Take a small strip of magnesium and burn it. It burns brilliantly and produce white ashes of magnesium oxide due to reaction between magnesium and oxygen. Collect the ashes of magnesium and add some distilled water to it. Test the solution with red and blue litmus papers. Note the changes in table.

Take a small amount of powdered sulphur in a deflagrating spoon and heat it. Sulphur starts burning and forms sulphur dioxide. Introduce the spoon into a jar and cover the jar with a lid to ensure that the gas produced does not escape. Add small quantity of water into the jar quickly replace the lid. Shake the jar well. Check the solution with blue and red litmus papers. Record the changes in table.

From the table we can observe metallic oxide solutions are basic in nature whereas non metallic oxide solutions are acidic in nature.

Activity – 6

Question 6.
Experiment about reaction of metals with water.
Answer:
Take a 500 ml beaker or a big trough and fill half of it with water. Cut a small piece of sodium (which is kept in kerosene) and put the sodium piece in water using forceps. This piece of sodium floats on the surface of water with a hissing sound.

This shows that sodium is reacting extremely fast with water.
Repeat the same experiment using aluminium, and iron. We will not see any change even after five minutes. This is because these metals react extremely slow with water. This shows metals react with water at different rates.

Activity – 7

Question 7.
Reaction with Acids.
Fill the reactions of the following metals and non-metals with dilute hydrochloric acid and dilute sulphuric acid.
Iron, Zinc, Copper, Sulphur, Aluminium, Graphite, Magnesium and Iodine.

Observation:
We find that some metals react with dilute HCl or H₂SO₄ liberating hydrogen but non-metals usually do not react with acids.

Activity – 8

Question 8.
Reactivity of metals:
Take six beakers and label them a, b, c, d, e and f. Take 50 ml of water in each beaker and dissolve a spatulaful of copper sulphate in beakers ‘a’ and ‘b’. Dissolve a spatulaful of zinc sulphate, in beakers ‘c’ and ‘d’. Iron sulphate in beakers ‘e’ and ‘f’.

• Zinc granules in beaker ‘a and e’
• Iron nail in beaker ‘b and d’
• Copper turnings in beaker ‘c and f’

Leave the beakers undisturbed. Record the changes in the colour of the solution in the table.

a) What could be the reasons behind these changes?
Answer:
In beaker ‘a’, zinc displaces copper from copper sulphate giving rise to colourless zinc sulphate. Iron displaces copper from copper sulphate in beaker ’b’ leaving light green colour of iron sulphate and zinc displaces iron from Iron sulphate by change the colour from light green to colour less:
Copper sulphate + Zinc → Zinc sulphate + Copper
Copper sulphate + Iron → Iron sulphate + Copper
Iron sulphate + Zinc → Zinc sulphate + Iron

b) Do you find any changes in beakers c, d and f?
Answer:
There is no change in beakers c, d and f. The reason is

1. Copper is unable to displace zinc from zinc sulphate in beaker ‘c’.
2. Copper is unable to displace iron from iron sulphate in beaker ‘f’.
3. Iron is unable to displace zinc from zinc sulphate in beaker ‘d’.

c) Why does iron is unable to displace zinc from zinc sulphate?
Answer:
Iron is less reactive than zinc. A more reactive metal can replace a less reactive metal from its salt solution. But a less reactive metal unable to displace a more reactive metal from its salt solution.
The order of reactivity of given metals are Zinc > Iron > Copper

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 3 Matter Around Us Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 3rd Lesson Matter Around Us

8th Class Physical Science 3rd Lesson Matter Around Us Textbook Questions and Answers

Improve Your Learning

Question 1.
Describe an activity which provides the evidence for
a) the motion of particles
b) attraction between particles
c) inter-particle space
Answer:
a) An activity which provides the evidence for the motion of particles:
Materials required: Two 250 ml round bottom flasks, red or blue ink, dropper, Potassium permanganate (KMnO₄) solution.
Procedure:

1. Take two 250 ml round bottomed flasks and fill them with water.
2. Use a dropper and put a few drops of blue or red ink slowly along the sides of first flask.
   
3. Use a dropper and put one or two drops of KMnO₄ solution along the sides of second flask.
4. We observe that in the first flask the ink drops slowly diffusing and mix with water, so as to change the colour of water to red/blue.
5. In the second flask we observe that the KMnO₄ solution diffuses fast in the water and the colour of water changes.
6. This activity provides an evidence for the motion of particles.

b) An activity which provides the evidence for the attraction between particles:

1. Open a water tap and allow the water to reach the ground.
2. Now try to break the stream of water with your finger.
3. We can break the stream momentarily, but not permanently.
4. The reason behind the stream of water remaining together is the force of attraction between the water particles.
5. Now try to break a piece of iron nail with your hands.
6. We cannot break it, because the force of attraction between the particles of nail is very high.
7. Do the same with a piece of chalk. We can break it easily, due to the weak attraction forces among the particles of piece of chalk.
8. From the above, we can say that the particles of matter have attractive forces among them to keep the particles together.
9. These forces of attraction are not equally strong in all the forms of matter.

c) An activity which provides the evidence for the inter-particle space:
Materials required: Beaker, water, salt, spoon and a glass rod.
Procedure:

1. Take a graduated beaker and fill it with some water and mark the level of water.
2. Add some salt and stir it thoroughly with a glass rod.
3. Observe the change in water level. There will be no change in it.
   
4. Add some more salt and stir it again.
5. Observe the change in water level. There will be no change.
6. Continue this process till you see some salt remains undissolved in water.
7. From this activity, we can say that solid and liquid particles have some space between them.
8. The solid particles enter into the space between the liquid particles on dissolving solid in liquid.
9. This process continues till all the space in liquid particles is occupied by solid particles.
10. After completion of this occupation, the solid particles, as there is no space to occupy remain undissolved.

Question 2.
Name the characteristics of matter that are demonstrated by diffusion.
Answer:
The characteristics of matter that are demonstrated by diffusion:

1. Matter is made up of tiny particles.
2. Particles of matter have space between them.
3. Particles of solids and liquids diffuse into liquids.
4. Particles of gases diffuse into gases.
5. Rate of diffusion of gases is higher than that of liquids or solids.
6. Particles of solids occupy the space between the particles of liquids on addition of a solid to a liquid.
7. Particles of matter move continuously in liquids and gases.

Question 3.
“When sugar is dissolved in water, there is no increase in volume.” Is it true or false? Comment on the statement keeping in mind the amount of sugar, amount of water, etc.
Answer:
This statement is true.
Reason: When sugar is dissolved in water, the particles of sugar occupy the space between the particles of water. Hence there is no change in the volume of water.
Conditions for observing the change in volume of water:
If we go on adding sugar without increasing the quantity of water, there will be no space between water particles, to be occupied by sugar particles. Hence the sugar remains undissolved.

Question 4.
Is there any change in mass when a substance changes its state? Explain with example.
Answer:

1. Take a beaker and fill it with ice cubes.
2. Find the mass (m₁) of the beaker along with ice cubes using a spring balance.
3. Keep the beaker at rest for some time, till the ice changes into water.
4. Then find the mass (m₂) of the beaker along with water.
5. We observe that m₁ = m₂.
6. We conclude that the mass never changes when a substance changes its state.

Question 5.
Do all substances change from solid to liquid and liquid to gas on heating ? Explain. Ans. All substances cannot change from solid to liquid and liquid to gas on heating.
e.g.:

1. When wood is heated, it cannot change its state from solid to liquid, but the form of substance changes.
2. Mercury/blood.

Question 6.
Define the following terms:
a) Melting point
b) Boiling point
c) Evaporation
Answer:
a) Melting point: The temperature at which a solid melts to become a liquid is called “melting point”.
b) Boiling point: The temperature at which a liquid starts boiling at the atmospheric pressure is known as its “boiling point”.
c) Evaporation : The phenomena of change of a liquid into vapours at any temperature below its boiling point is called “evaporation”.

Question 7.
Correct the following statements.
a) Water boils at 100°C under atmospheric pressure.
Answer:
This is a correct statement.

b) A liquid evaporates above its boiling point.
Answer:
This statement is incorrect.
Reason: Evaporation takes place at any temperature below its boiling point.

c) Solids have the largest inter-particle space.
Answer:
This statement is incorrect.
Correct Statement: The inter-particle space of solids is minimum.
Explanation: The force of attraction between the particles is also very high due to less inter-particle space. Hence solids have definite shape and a fixed volume.

d) Gases have the strongest inter-particle forces.
Answer:
This statement is incorrect.
Correct Statement: Gases have weakest inter-particle forces.
Explanation: The inter-particle space for a gas is maximum. Hence the inter-particle forces are also weak. Due to this gases have no definite shape or fixed volume. They have to be stored in a closed container always.

Question 8.
Why do we prefer to sip hot tea with a saucer rather than a cup ?
Answer:

1. The surface area of saucer is more than the surface area of a cup.
2. We know that the rate of evaporation increases with an increase of surface area.
3. The hot tea particles can easily escape from the saucer than a cup.
4. Hence hot tea becomes cold easily in a saucer than a cup.
5. So we prefer to sip hot tea with a saucer rather than a cup.

Question 9.
When water solidifies to ice then heat is
a) Liberated
b) Absorbed
c) No change
d) Depending upon the condition heat may absorbed or liberated.
Answer:
a) Liberated

Question 10.
Convert the following temperatures to the Celsius scale.
a) 283 K   b) 570 K
Answer:
a) We know that 273 K = 0°C
283 K = 283 – 273 = 10°C
∴ 283 K = 10°C

b) We know that 273 K = 0°C
570 K = 570 – 273 = 297
∴ 570 K = 297°C

Question 11.
Convert the following temperatures to the Kelvin scale,
a) 27°C   b) 367°C
Answer:
a) 27°C = 27 + 273 = 300 K
b) 367°C = 367 + 273 = 640 K

Question 12.
Fill in the blanks.
a) Matter changes from one state to another either raising the …………… or lowering the ……………..
b) A change in which a solid on heating directly changes into vapour state is called …………….
Answer:
a) temperature, temperature
b) sublimation

Question 13.
Match the following.
a) Conversion of liquid into gas      ( )        (i) gas
b) Non – compressible                    ( )        (ii) solid
c) Maximum expansion                   ( )        (iii) particle
d) Constituents of matter                ( )        (iv) evaporation
Answer:
a) iv
b) ii
c) i
d) iii

Question 14.
How can we smell perfume sitting several meters away from the source?
Answer:

1. We know that the particles of gas are highly mobile in the air.
2. The particles of perfume vapours also move in air for several meters.
3. Hence we can smell perfume, sitting several meters away from the source.

Question 15.
Steam produces more severe burns than boiling water. Think why?
Answer:

1. Steam particles have more energy than the particles of boiling water.
2. This is because particles in water vapour have absorbed additional energy in the form of latent heat of vaporization.
3. So, steam produces more severe burns than boiling water.

Question 16.
Make a model to explain the structure of particles in solids, liquids and gases.
Answer:
Students have to prepare their own models.

Question 17.
How do you appreciate sweating mechanism of human body to control the temperature of the body?
Answer:

1. When we do some physical exercise or hard work, sweating is observed on the body.
2. The sweat evaporates from the surface of our body by absorbing the heat from your body.
3. Thus the particles of liquid absorb energy from our body and escapes to the surroundings.
4. Due to this we feel cool.

Different shaped containers, Beaker, Measuring jar, Conical flask, Round bottomed flask, Test tubes, CNG related Pictures, 50 ml syringe, Incense stick, Scent bottle, Potassium permanganate, Copper sulphate, Long glass tube with scale, Liquid Ammonia, Hydrochloric acid, Cotton, Two rubber corks, Two tongs, Dropper, Water, Salt, Thermometer, Spirit lamp, China dish.

8th Class Physical Science 3rd Lesson Matter Around Us InText Questions and Answers

8th Class Physical Science Textbook Page No. 31

Question 1.
Is there any substance which can be found in three states like water?
Answer:
Yes. The substance which can be found in three states like water is wax.

Question 2.
What are the properties that lead us to consider petrol or milk as liquids?
Answer:
Petrol and milk are considered as liquids because they have no fixed shape. But they get the shape of the container in which they have been poured.

Question 3.
Do solids have definite shape and fixed volume?
Answer:
Yes, solids have definite shape and fixed volume.

8th Class Physical Science Textbook Page No. 32

Question 4.
What is the shape of the water in different containers?
Answer:
Water gets the shape of containers in which it has been poured.

Question 5.
Is it same in all cases or different?
Answer:
Yes, it is same in all cases.

Question 6.
What shape does water take if it spills on the floor?
Answer:
Water spreads on floor if it spills on the floor.

Question 7.
Are the levels of water and milk same?
Answer:
Yes, the levels of water and milk are same.

Question 8.
Can you guess the volume of oil?
Answer:
Volume of the oil is equal to 50 ml.

Question 9.
What does a fluid mean?
Answer:
Fluid is a substance which can flow easily.

8th Class Physical Science Textbook Page No. 33

Question 10.
Does CNG have a fixed volume?
Answer:
No, CNG does not have a fixed volume.

Question 11.
Does CNG have a definite shape?
Answer:
No, CNG doesn’t have a fixed shape. Its shape is depending on the containers.

8th Class Physical Science Textbook Page No. 34

Question 12.
Does the smell from burning incense stick and deodorant spray reach someone on the other end at the same time?
Answer:
The smell from deodorant spray reaches someone on the other end faster than the smell from incense stick.

8th Class Physical Science Textbook Page No. 36

Question 13.
Why do gases diffuse faster than solids and liquids?
Answer:
The molecules in the gas are far from each other i.e., the inter molecular space is very high than in solids and liquids. Hence they have less attractive power. So, gases diffuse faster than solids and liquids.

Question 14.
When does water change into ice and then into vapour?
Answer:
Water when cooled in a refrigerator, it becomes ice. (Decreasing the temperature).

8th Class Physical Science Textbook Page No. 39

Question 15.
What type of changes occur inside the matter during a change of state?
Answer:
Inside the matter, we observe the increase/decrease in volume during the change of state.

Question 16.
How does this change of state take place?
Answer:
Change of state takes place by change in temperature.

Question 17.
What does happen to the particles of matter during a change of state?
Answer:
During a change of state, the kinetic energy of particles may increase/decrease, resulting in the increase/decrease of inter molecular attraction.

8th Class Physical Science Textbook Page No. 41

Question 18.
What will does happe when we apply pressure and compress a gas enclosed in a cylinder?
Answer:
When pressure is applied and compressed the volume of a gas in a cylinder decreases. (According to Boyle’s law).

Question 19.
Will the particles come closer?
Answer:
Yes, the inter molecular space between the particles decreases and they come close.

Question 20.
Do you think that increasing or decreasing the pressure can change the state of matter?
Answer:
Change in pressure can change the state of matter.

Question 21.
Can we liquify gases by applying pressure or reducing temperature?
Answer:
Gases can be liquefied by cooling below its critical temperature. Hence, change in temperature and pressure causes the gases to liquefy.

Question 22.
Do we always need to supply heat or change the pressure for changing the state of matter?
Answer:
It is required. But in some cases like natural evaporation of water, it is not necessary.

Question 23.
Can the change of state from liquid to vapour take place without the liquid reaching its boiling point?
Answer:
Yes, it is possible in case of drying the wet clothes. In the process, water direly changes into vapour form without reaching its boiling point.

Question 24.
Can you give few more examples for evaporation?
Answer:
Evaporation of iodine, drying up of wet body, etc.

Question 25.
What could be the reasons for this type of changes in states?
Answer:
In liquid s, the particles at the surface possess higher energy than particles in the bulk of watt.. The particles on the surface are able to break away from the force of attraction of other particles and change into vapour state.

Think & Discuss

8th Class Physical Science Textbook Page No. 34

Question 1.
Rubber band Activity:
a) Let us stretch a rubber band. Is there a change in its shape?
b) Is rubber band solid or liquid? Why?
Answer:
a) When rubber band is stretched it changes its shape.
b) It is a solid. If stretching is stopped, the rubber band regains its shape. If the stretching is too much, the rubber band permanently loses its shape.
Reason : Rubber band is a solid, but the nature of particles by which the rubber band is made is responsible for the above phenomena.

Question 2.
Powdered salt Activity:
a) Which shape does the powdered salt take?
b) Can you say that salt is a liquid on the basis of change in its shape? Justify your answer. Take a sponge. Observe its shape.
Answer:
a) Powdered salt takes the shape of the container, b) It is a solid.
Justification:

1. Change in shape or state means a complete change in the arrangement of particles.
2. Powdered salt is a composition of tiny particles, which do not change their shape.

Question 3.
Sponge Activity:
Can you compress it? Is it a soild? Why? Think. Is anything coming out from the sponge when it is compressed.
Answer:

1. Sponge can be compressed.
2. It is a solid.

Justification :

1. The inter-particle space is slightly more than a rigid body.
2. So that it can be compressed.

Question 4.
Why can’t you able compress a wooden block ? (or) Why aren’t you able to compress a wooden block ?
Answer:

1. The inter-particle space is very less in a wooden block.
2. So we cannot compress it at ordinary conditions.

8th Class Physical Science Textbook Page No. 42

Question 5.
Why do we wear cotton clothes in summer?
Answer:

1. More sweat is produced from our body during summer due to excess of external temperature.
2. We feel cool when the sweat is evaporated.
3. On wearing cotton clothes, the clothes absorb sweat from our body. So, we feel cool.
4. Other clothes like silk, polyester, etc. cannot absorb sweat.
5. Hence we wear cotton clothes in summer.

Question 6.
Why do we see water droplets on outer surface of a glass containing ice-cold water?
Answer:

1. Ice-cold water in the glass cools its surface.
2. Air around the glass contains water vapour which is warmer than the surface of the glass.
3. Due to the cold glass, air close to its surface will also become cooler.
4. This changes the water vapour in the air around the surface of the glass into water.
5. This water forms small drops on the outer surface of the glass.

Question 7.
Why do pigs toil in the mud during hot summer?
Answer:

1. Generally, the temperature of body is controlled through the sweating evaporation.
2. In the case of pigs, these have less sweat pores on their skin surfaces. So sweating evaporation process does not take place.
3. Because of this type of arrangement in pigs, they toil in the mud ponds more time during hot summer.

8th Class Physical Science 3rd Lesson Matter Around Us Activities

Activity – 1

Identifying the shape and volume of liquids
Question 1.
(a) Prove that the liquids have no fixed shape.
Answer:

1. Collect transparent containers of different shapes.
2. Take some water using the measuring jar.
3. Pour the water in one of the containers.
4. Observe the shape of water.
5. Pour the same water in different containers and observe the shape of water.
6. We observe that the water (liquid) takes the shape of container.
7. We can say that liquids have no fixed shape.
   

(b) Prove that the liquids have fixed volume.
Answer:

1. Take 50 ml of water with a measuring jar.
2. Pour this water in a transparent beaker.
3. Mark the level of water on the beaker and throw the water out.
4. Now measure 50 ml of milk, and pour it in the same beaker.
5. Mark the level of milk on it, and remove milk from the beaker.
6. Now take 50 ml of oil and pour it in the same beaker.
7. Mark the level of oil on it, and remove the oil from the beaker.
8. We observe that the mark on the beaker is same for water, milk and oil.
9. This proves that the liquids have a fixed volume.

Activity – 2

Question 2.
Do the gases have a definite shape and a fixed volume?
Answer:
CNG (Compressed Natural Gas) is stored in a tank. In vehicles CNG is stored in cylinders. We observe that CNG and all other gases neither have a fixed shape nor fixed volume.

Activity – 3

Observing the compressibility of different materials
Question 3.
Prove that the gases are highly compressible than liquids and solids.
Answer:

1. Take a 50 ml syringe.
2. Draw the piston to suck in air.
   
3. Place your finger on the nozzle and press.
4. Observe depth of piston moved into syringe and note the height of air column.
5. We feel hard to press the piston after certain height.
6. Here the air in the syringe is compressed.
7. Now fill water in the syringe and do the same experiment.
8. Note the height of water column when you feel hard to press the piston.
9. Here the height of water column is more than the height of air column.
10. Now take a piece of wood or iron and press it with your thumb.
11. We cannot find any observable change in its volume.
12. From the above observations, we can say that gases are highly compressible than liquids and solids.

Activity – 4

Observing the diffusion of gases
Question 4.
Describe an activity to observe the diffusion of gases.
Answer:

1. Ask your friend to hold an unlit incense stick and stand in one corner of the room.
2. Then you go and stand in the other corner.
3. We cannot observe any smell (This depends on the type of incense stick).
4. Now ask your friend to light the incense stick.
5. After a few seconds, we can observe the smell of incense stick.
6. The scent in the vapour form and smoke mixes with air and moves across the room and reaches our nose.
7. This activity proves that the gases can diffuse.

Activity – 5

Observing the diffusion of liquids
Question 5.
Write an activity which shows the diffusion of liquids.
Answer:
Take 250 ml round bottomed flask with 2/3rd water in it. Use a dropper and put a few drops of blue or red ink or Potassium permanganate (KMnO₄) solution slowly along the sides of the flask.

We can observe that liquids also diffuse into each other like gases.

Activity – 6

Observing the diffusion of particles of solids into liquids
Question 6.
Prove that the particles of solids diffuse into liquids.
Answer:

1. Take a beaker full of water.
2. Add a few crystals of potassium permanganate to it.
3. We observe that the diffusion of potassium permanganate crystal into water and the colour of water changes.
4. Repeat the experiment with crystals of copper sulphate.
5. Here also we observe the diffusion of CuSO₄ crystals into water and the colour of water changes.
6. From the above observations, we found that the particles of solids diffuse into liquids.

Lab Activity Diffusion of two gases
Question 7.
Describe an experiment to measure the speed of diffusion of two gases.
Answer:
Aim: To observe the speed of diffusion of two gases.
Materials required : Long glass tube with scale, liquid ammonia, Hydrochloric acid (HC/), pieces of cotton, two rubber corks and two tongs.

Procedure:

1. Take a one meter long narrow glass tube.
2. Take two pieces of cotton wool.
3. Soak one piece of cotton wool in HCl solution.
4. Soak another piece of cotton wool in NH₃ solution.
5. Insert them separately at the two ends of the tube with the help of tongs.
6. Close the ends of the glass tube with rubber cork and observe.
7. The HCl gives off hydrogen chloride gas and ammonia solution gives off ammonia gas.

Observation:

1. Both gases react together to form a white ring in the tube due to formation of ammonium chloride.
2. Measure the distance of white ring from two ends of the glass tube.

Explanation:
We can observe that the ammonia gas travelled faster. So that the distance of white ring is more from ammonia end than hydrochloric acid end.

Activity – 7

Question 8.
How small are the particles of matter?
Answer:

1. Take a beaker with water. Mark the level of water.
2. Add 1 or 2 crystals of potassium permanganate and dissolve in water.
3. Colour of water changes to light violet.
4. Now take out approximately 10 ml of this solution and add it to 90 ml of clear water in another beaker.
5. Now the colour of water will be lighter than in the previous one.
6. Again take out 10 ml of this solution and add it to another 90 ml of clear water.
7. Carry out this process 4, 5 times and observe the changes in colour of the solution.
8. We observe the water in last beaker also changed to light violet.
9. From this activity we conclude that both solids and liquids are made up of tiny particles.

Activity – 8

There exists space between particles
Question 9.
Write an activity which shows the space between particles.
Answer:

Procedure: Take a graduated beaker and fill it with some water and mark the water level. Add some salt and stir it thoroughly with a glass rod. Observe if there is any change in water level. Add some more salt and stir it again.
Observations: From the activity we can conclude that both solid and liquid particles have some space between them. Hence the solid particles enter into the space between the liquid particles on dissolving solid in liquid. So there is no change in the water level.

Activity – 9

Observing the force of attraction between the particles of matter
Question 10.
Write an activity which provides an evidence for the force of attraction between the particles of the matter.
Answer:
Procedure:
Open a water tap and allow the water to reach the ground. Now try to break the stream of water with our finger. But we cannot break the stream permanently.
We cannot also break a piece of iron nail with our hands. But we can break a piece of chalk with our hands.
Observations: From the above observations we can say that particles of the matter have forces acting between them that keeps the particles together.
It is also clear that this force is not equally strong and different in different forms of matter.

Activity – 10

Effect of temperature on change of state
Question 11.
Write an activity to know the effect of temperature on change of state of matter.
Answer:

1. Take about 100 g of ice in a beaker.
2. Suspend a laboratory thermometer so that its bulb is in contact with the ice.
3. Set up the beaker as shown in the figure.
4. Note the temperature.
5. Now heat the beaker slowly.
   
6. Record the change in temperature after every 30 seconds.
7. Let the ice melt completely.
8. Now place a glass rod in the beaker and continue heating till water starts boiling.
9. After some time all the water will get vapourised.
10. From this we understand that substances around us change state from solid to liquid and from liquid v to gas on application of heat.
11. There are some substances which can change directly from solid state to gaseous state and vice versa without changing into the liquid state.

Activity – 11

Effect of surface area, humidity and wind speed on evaporation
Question 12.
(a) Explain the effect of surface area on the rate of evaporation.
Answer:
Rate of evaporation increases with an increase of surface area.
Explanation:

1. During evaporation process, the particles escape from the surface of liquid.
2. The increase in the surface area provides more scope for particles to escape from the surface.
3. Hence it leads to increase the rate of evaporation.

Ex: Water in a China dish evaporates faster than the water in test tube.

(b) Explain the effect of humidity on the rate of evaporation.
Answer:
Rate of evaporation decreases with the increase in humidity.
Explanation:

1. The amount of water present in air is called humidity.
2. The air around us cannot hold more than a definite amount of water vapour at a given temperature.
3. If the amount of water vapour is high in air, then the rate of evaporation decreases. Ex : Clothes dry slowly on a rainy day than on a normal day.

(c) Explain the effect of wind speed on rate of evaporation.
Answer:
Rate of evaporation increases with the increase in wind speed.
Explanation:

1. Because of increase in wind speed, particles of water vapour move away with the wind.
2. Due to this, amount of water vapour in the surroundings decreases.
3. It leads to increase in the rate of evaporation.
   Ex: Clothes dry faster on a windy day or under fan than a normal day.