CBSE Class 6

These NCERT Solutions for Class 6 Maths Chapter 1 Knowing Our Numbers Ex 1.2 Questions and Answers are prepared by our highly skilled subject experts.

NCERT Solutions for Class 6 Maths Chapter 1 Knowing Our Numbers Exercise 1.2

Question 1.
A book exhibition was held for four days in a school. The number of tickets sold at the counter on the first, second, third and final day was respectively 1094,1812, 2050 and 2751. Find the total number of tickets sold on all the four days.
Answer:
Number of tickets sold on first day = 1,094 Number of tickets sold on second day = 1,812
Number of tickets sold on third day = 2,050
Number of tickets sold on fourth day = 2,751
Total tickets sold = 7,707
Therefore, 7,707 tickets were sold on all the four days.

Question 2.
Shekhar is a famous cricket player. He has so far scored 6980 runs in test matches. He wishes to complete 10,000 runs. How many more runs does he need?
Answer:
Runs to achieve = 10,000
Runs scored = 6,980
Runs required = 10000 – 6980 = 3,020
Therefore, he needs 3,020 more runs.

Question 3.
In an election, the successful candidate registered 5,77,500 votes and his nearest rival secured 3,48,700 votes. By what margin did the successful candidate win the election?
Answer:
Number of votes secured by successful candidates = 5,77,500
Number of votes secured by his nearest rival = 3,48,700
Margin between them = 2,28,800
Therefore, the successful candidate won by a margin of 2,28,800 votes.

Question 4.
Kirti bookstore sold books worth ? 2,85,891 in the first week of June and books worth ? 4,00,768 in the second week of the month. How much was the sale for the two weeks together? In which week was the sale greater and by how much?
Answer:
Books sold in first week = 2,85,891
Books sold in second week = 4,00,768
Total books sold = 6,86,659
Since, 4,00,768 – 2,85,891
Therefore sale of second week is greater than that of first week.
More books sold in second week = 1,14,877
Therefore, 1,14,877 more books were sold in second week.

Question 5.
Find the difference between the greatest and the least 5-digits number that can be written using the digits 6, 2, 7, 4, 3 each only once.
Answer:
Greatest five-digit number using digits 6, 2, 7, 4, 3 = 76,432
Smallest five-digit number using digits 6, 2, 7, 4, 3 = 23,467
Difference = 76,432 – 23,467 Therefore the difference is 52,965.

Question 6.
A machine, on an average, manufactures 2,825 screws a day. How many screws did it produce in the month of January 2006?
Answer:
Number of screws manufactured in one day = 2,825
Number of days in the month of January (31 days) = 2,825 x 31 = 87,575
Therefore, the machine produced 87,575 screws in the month of January.

Question 7.
A merchant had ₹ 78,592 with her. She placed an order for purchasing 40 radio sets at ₹ 1,200 each. How much money will remain with her after the purchase?
Answer:
Cost of one radio = ₹ 1200
Cost of 40 radios = 1200 x 40 = ₹ 48,000
Now, total money with merchant = ₹ 78,592
Money left with her ₹ 78,592 – ₹ 48,000 = ₹ 30,592
Therefore, ₹ 30,592 will remain with her after the purchase.

Question 8.
A student multiplied 7236 by 65 instead of multiplying by 56. By how much was his answer greater than the correct answer? (Hint: Do you need to do both the multiplications?)
Answer:
Wrong answer = 7236 x 65
Correct answer = 7236 x 56

Difference in answers
= 470340 – 405216 = 65,124.

Question 9.
To stitch a shirt 2 m 15 cm cloth is needed. Out of 40 m cloth, how many shirts can be stitched and how much cloth will remain? (Hint: convert data in cm.)
Answer:
Cloth required to stitch one shirt = 2 m
15 cm = 2 x 100 cm + 15 cm = 215 cm
Length of cloth = 40 m = 40 x 100 cm = 4000 cm
Number of shirts can be stitched

Therefore, 18 shirts can be stitched and 130 cm (1 m 30 cm) cloth will remain.

Question 10.
Medicine is packed in boxes, each weighing 4 kg 500 g. How many such boxes can be loaded in a van which cannot carry beyond 800 kg?
Answer:
The weight of one box = 4 kg 500 g
= 4 x 1000 g + 500 g = 4500 g
Maximum load can be loaded in van
= 800 kg = 800 x 1000 g = 800000 g
Number of boxes = \(\frac{800000}{4500}\)

Therefore, 177 boxes can be loaded.

Question 11.
The distance between the school and a student’s house is 1 km 875 m. Every day she walks both ways. Find the total distance covered by her in six days.
Answer:
Distance between school and home = 1.875 km
Distance between home and school = 1.875 km
Total distance covered in one day = 3.750 km
Distance covered in six days = 3.750 x 6 = 22.500 km.
Therefore, 22 km 500 m distance covered in six days.

Question 12.
A vessel has 4 litres and 500 mL of curd. In how many glasses each of 25 mL capacity, can it be filled?
Answer:
Capacity of curd in a vessel
= 4 litres 500 mL
= 4 x 1000 mL + 500 mL
= 4500 mL
Capacity of one glass = 25 mL
Number of glasses can be filled = \(\frac{4500}{25}\)

Therefore, 180 glasses can be filled by curd.

These NCERT Solutions for Class 6 Maths Chapter 1 Knowing Our Numbers Ex 1.1 Questions and Answers are prepared by our highly skilled subject experts.

NCERT Solutions for Class 6 Maths Chapter 1 Knowing Our Numbers Exercise 1.1

Question 1.
Fill in the blanks:
(a) 1 lakh = ……………. ten thousand.
(b) 1 million = ……………. hundred thousand.
(c) 1 crore = ……………. ten lakh.
(d) 1 crore = ……………. million.
(e) 1 million = ……………. lakh.
Answer:
(a) 10
(b) 10
(c) 10
(d) 10
(e) 10

Question 2.
Place commas correctly and write the numerals:
(a) Seventy-three lakh seventy-five thousand three hundred seven.
(b) Nine crore five lakh forty-one.
(c) Seven crore fifty-two lakh twenty- one thousand three hundred two.
(d) Fifty-eight million four hundred twenty-three thousand two hundred two.
(e) Twenty-three lakh thirty thousand ten.
Answer:
(a) 73,75,307
(b) 9,05,00,041
(c) 7,52,21,302
(d) 58,423,202
(e) 23,30,010

Question 3.
Insert commas suitably and write the names according to Indian System of Numeration:
(a) 87595762
(b) 8546283
(c) 99900046
(d) 98432701
Answer:
(a) 8,75,95,762: Eight crore seventy-five lakh ninety-five thousand seven hundred sixty-two.
(b) 85,46,283: Eight-five lakh forty-six thousand two hundred eighty-three.
(c) 9,99,00,046: Nine crore ninety-nine lakh forty-six.
(d) 9,84,32,701: Nine crore eighty-four lakh thirty-two thousand seven hundred one.

Question 4.
Insert commas suitably and write the names according to International System of Numeration:
(a) 78921092
(b) 7452283
(c) 99985102
(d) 48049831
Answer:
(a) 78,921,092: Seventy-eight million nine hundred twenty-one thousand ninety-two.
(b) 7,452,283: Seven million four hundred fifty-two thousand two hundred eighty-three.
(c) 99,985,102: Ninety-nine million nine hundred eighty-five thousand one hundred two.
(d) 48,049,831: Forty-eight million forty nine thousand eight hundred thirty one.

These NCERT Solutions for Class 6 Science Chapter 16 Garbage In, Garbage Out Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Garbage In, Garbage Out NCERT Solutions for Class 6 Science Chapter 16

Class 6 Science Chapter 16 Garbage In, Garbage Out Textbook Exercise Questions and Answers

Question 1.
a.Which kind of garbage is not converted into compost by the red worms?
b. Have you seen any other organism besides redworms, in your pit? If yes, try to find out their names. Draw pictures of these.
Answer:
a. The garbage which consists of cloth, broken glass, aluminium wrappers, polythene bags, nails, broken toys and old shoes cannot be converted into compost by red worms,

b. Yes, a pit might contain other soil microbes such as bacteria, other species of earthworms such as brandling worm and red wiggler worm.

Question 2.
Discuss:
a. Is garbage disposal the responsibility only of the government?
b. Is it possible to reduce the problems relating to disposal of garbage?
Answer:
a. Proper disposal of garbage should be a concern of every citizen, and not just of the government. Each and every individual must reduce activities that pollute the environment. A lot of waste is generated from homes, offices, schools, hospitals, etc. It includes food waste, paper, plastic, glass, metal, etc. Therefore, it is required that every individual must reduce the production of wastes and must help in the proper disposal of these wastes.

b. Yes, it is possible. Here are some steps that can be observed by every individual to reduce the problem of garbage disposal:

• Avoid using plastic bags. Encourage shopkeepers to use paper bags or always carry a cloth or jute bag while shopping
• Save paper. Use both sides of paper to write.
• Use separate bins for recyclable and non-recyclable waste.
• Kitchen waste that includes fruit and vegetable peels, waste food, tea leaves, etc., can be used to make manure.
• Encourage your family, friends, and others to follow proper disposal practices.

Question 3.
a. What do you do with the leftover food at home?
b. If you and your friends are given the choice of eating in a plastic plate or a banana leaf platter at a party, which one would you prefer and why?
Answer:
a. Leftover food at home along with other kitchen waste like vegetable peel, paper are dumped into compost pit to convert them into manure. Later on manure is used to grow plants.

b. We will select banana leaf platter because it can be easily converted into manure by composting. Plastic plate can be recycled but in this process it gives out harmful gases which pollute the environment. Plastic items cannot be converted into manure by composting.

Question 4.
a. Collect pieces of different kinds of paper. Find out which of these can be recycled.
b. With the help of a lens, look at the pieces of paper you collected for the above question. Do you see any difference in the material of recycled paper and a new sheet of paper?
Answer:
a. Most of the papers available in market are recyclable, i.e., newspapers, notebooks, magazines, paper sheets, envelopes, etc.
b. The difference between new sheet and recycled paper is that the surface of new sheet is smooth whereas that of recycled paper is rough.

Question 5.
a. Collect different kinds of packaging material. What was the purpose for which each one was used? Discuss in groups.
b. Give an example in which packaging could have been reduced?
c. Write a story on how packaging increases the amount of garbage.
Answer:
a. Packaging materials like thermocol, foam sheets, paper cuttings, cardboard and jute are used to protect the articles. Cardboard boxes, plastic containers and tin containers are used to facilitate transportation of the packed materials.

b. Packaging of toys, clothes, shoes, chocolates can be reduced.

c. We use packaging materials to protect the articles and also to make package good-looking. For example, to give a gift on birthday, the gift is packed and wrapped in a shiny paper or plastic-coated paper. After use the packing material is thrown in dustbin. Similarly, plastic bags, cans, aluminium foils, plastic or aluminium cans and other packaging materials are used and thrown out after use. Many things such as ghee, refined oil, soaps, detergents and most of eatable goods are sold in small packets. All of this increases the garbage due to packing.

Question 6.
Do you think it is better to use compost instead of chemical fertilisers? Why?
Answer:
Yes, compost is better than chemical fertilisers because:

• Compost is eco-friendly and does not pollute the environment. Fertility and texture of the soil is maintained while using compost.
• The natural composition of the soil is affected while using fertilizers and some of them are even toxic in nature at higher quantities.
• Compost is easy to make and cheap whereas fertilisers are costly and also harmful.
• Compost is easier to prepare.

NCERT Extended Learning Activities And Projects

Question 1.
Collect old and discarded objects and materials like glass bottles, plastic bottles, coconut husk, wool, bedsheets, greeting cards and any other thing.
Can you make something useful out of these, instead of throwing them? Try.
Hint.
Do it yourself.

Question 2.
Prepare a detailed project report on compost making activity you did in school.
Hint.
Do it yourself.

Class 6 Science Chapter 16 Garbage In, Garbage Out Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is vermicomposting?
Answer:
Vermicomposting is a method of composting where compost is made from biodegradable waste with the help of redworms.

Question 2.
What is redworm?
Answer:
It is a type of earthworm used for composting.

Question 3.
Which organisms other than earthworm is involved in composting?
Answer:
Microorganisms such as bacteria, fungi etc., are involved in composting.

Question 4.
Suggest some packaging material which can be recycled or reused.
Answer:
Glass bottles, recycling polythene and jute bags.

Question 5.
List a few things we use that are made of plastics?
Answer:
Toys, shoes, bags, pens, combs, toothbrushes, buckets, bottles, water pipes, etc.

Question 6.
What are the uses of green-coloured bins?
Answer:
The green bins are for collecting kitchen and other plant or animal wastes.

Question 7.
When is rotting of garbage said to be completed?
Answer:
A black colour and no foul smell indicate that rotting of garbage is complete.

Question 8.
For what purpose are blue-coloured bins used?
Answer:
The blue bins are used for collecting waste materials that can be used again, such as plastics, metals and glass.

Question 9.
What is composting?
Answer:
The rotting and conversion of some materials into manure is called ‘composting’.

Question 10.
What is a landfill?
Answer:
Landfill is an area where the garbage collected from a city or town is dumped. The area is later converted into a park.

Question 11.
What kind of waste materials rot completely when buried in the soil?
Answer:
Waste materials such as kitchen, plants and animal waste rot completely when buried in the soil.

Question 12.
What does kitchen waste mainly consist of?
Answer:
Kitchen waste mainly consists of fruits and vegetable peels, eggshells, waste food and tea leaves.

Question 13.
Which items should not be included for making compost?
Answer:
Pieces of cloth, polythene bags, broken glass, aluminium wrappers, nails, old shoes, broken toys, etc.

Short Answer Type Questions

Question 1.
What should we do with the left-over food at home?
Answer:
We should do the following to the left-over food:

• Preserve food properly for reuse.
• Use it in preparation of some other food item and consume it.

Question 2.
Polythene bags should not be used for garbage disposal. Why?
Answer:
Plastics thrown carelessly get into drains and sewages which often results in blockage and causes water-logging. So polythene bags should not be used for garbage disposal.

Question 3.
What are the uses of plastics?
Answer:
Cleaning solution and soap containers, food and drink storage, shopping bags, freezer bags, pipes, insulation, bottle caps, vehicle fuel tanks, protective helmets, etc. are all made from plastics.

Question 4.
Why do polythene bags create a big problem in garbage disposal?
Answer:
Some kind of plastics can be recycled, but not all of them. Polythene bags and some plastics do not rot. Thus, polythene bags create a big problem in garbage disposal.

Question 5.
Why plastic should not be burnt?
Answer:
All kind of plastics give out harmful gases, upon heating or burning. These gases may cause many health problems, including cancer in humans. Thus, plastic should not be burnt.

Question 6.
Why is burning of husk, dried leaves and part of crop plants considered as bad practice? What could be a better alternative?
Answer:
Burning of these produces smoke and gases that are harmful to our health. We should try to stop such practices. These wastes could be converted into useful compost.

Question 7.
Why should we not use wastes that may contain salt, pickles, oil, vinegar, meat and milk preparations as food for redworms?
Answer:
We should not use wastes that may contain salt, pickles, oil. vinegar, meat and milk preparations as food for redworms because if you put these things in the pit, disease-causing small organisms start growing in the pit.

Question 8.
Suggest some handicrafts which can be prepared using waste materials.
Answer:
Files from old charts, greeting cards decorated with flowers made from pencil shavings, mats from old clothes, baskets from used old polythene bags and diary from invitation cards are some of the items which can be prepared using waste materials.

Question 9.
Rag pickers always suffer from diseases. Give reason.
Answer:

• Garbage dumps have flies, cockroaches and mosquitoes, which later turn into breeding grounds for micro-organisms that may cause several diseases.
• While picking through waste, the rag pickers put themselves at a great risk and are always prone to disease as the waste that they search through can be infected.

Question 10.
What are the effects of throwing garbage in open place?
Answer:
Effects of throwing garbage in open place are as follows:

• Garbage will start decaying and as a result of this, bad smell spreads in the nearby areas.
• It will become a breeding ground for mosquitoes and flies.
• It causes air and land pollution and thus causes many health problems.
• It destroys the aesthetic look of a place.

Question 11.
What is the role of a junk dealer? Do you think junk dealers help in waste management?
Answer:
The role of a junk dealer is collection of wastes from various sources. Yes, junk dealers help in waste management by segregating the wastes as recyclable and non-recyclable materials.

Question 12.
State one difference between composting and vermicomposting.
Answer:
Composting is a method in which biodegradable wastes such as vegetable peels, waste food, leaves, etc., can be recycled and converted into manure by burying them in compost pits. The method of making compost from kitchen wastes (or kitchen garbage) by using red worms is called vermicomposting. The compost made by using red worms is called vermicompost.

Long Answer Type Questions

Question 1.
What are the merits and demerits of using plastic?
Answer:
Merits of plastic:

• It is durable.
• It is low at cost.
• It is water resistant.
• It is lightweight.
• It is unbreakable.

Demerits of plastic:

• It gives out harmful gases upon heating or burning.
• It is non-biodegradable.
• If it is thrown carelessly on roads or other places, it gets into drains and sewer system and chokes them.

Question 2.
What can we do to minimise overuse of plastics and deal with garbage?
Answer:
We can do the following to minimise overuse of plastics and deal with garbage:

• We can make a minimum use of plastic bags. We can reuse the bags whenever it is possible to do so.
• We can insist shopkeepers to use paper bags. We can carry a cloth or a jute bag when we go out for shopping.
• We should not use plastic bags to store eatables.
• We should not throw plastic bags here and there, after use.
• We should never bum plastic bags and other plastic items.
• We should do not put garbage in plastic bags and throw it away.
• We should use vermicomposting at home and deal with our kitchen waste usefully.
• We can recycle paper.
• We should use both sides of the paper to write. We can use a slate for rough work. We can use blank sheets of paper left in our notebooks for rough work.

Question 3.
How can we make handmade paper?
Answer:
Steps to make handmade paper:

• Tear the paper into small pieces. Put them in a tub or a bucket and pour water in it.
• Let the pieces of paper remain submerged in water for a day. Make a thick paste of paper by pounding it.
• Now, spread the wet paste on the wire mesh fixed to the frame. Pat it gently to make the thickness of layer of the paste as uniform as possible.
• Wait till water drains off. Now, carefully remove the layer of paste from the frame, spread it on a sheet of newspaper in the sun.
• Keep the corners of the newspaper sheet pressed by putting some weights so that these do not curl up.
• Add food colour, pieces of dry leaves or flower petals or pieces of coloured paper in the paste before spreading it so as to get a recycled paper with beautiful patterns on it.

Question 4.
Distinguish between bio-degradable and non-biodegradable wastes.
Answer:
Biodegradable wastes:

1. The substances which get degraded to simpler and harmless substances over a period of time are known as biodegradable.
2. They are not harmful to animals and plants, e.g., cow dung, leaves, paper, etc.

Non-biodegradable wastes:

1. The substances which do not get degraded to simpler and harmless substances over a period of time are known as non-biodegradable.
2. They are harmful to plants and animals, e.g., DDT, plastic, polythene, etc.

Question 5.
What suggestions you will give to the members of your locality to solve the problem of waste materials?
Answer:
We will suggest the members of my locality to use biodegradable waste in preparing compost. To take people in confidence, we should make efforts to show the path for preparing compost:

• You should select a comer of your locality.
• Dig a pit at open place and ask all the residents to throw their kitchen waste in this pit. Cover the biodegradable waste in the pit with layers of soil.
• Cover the pit with the mixture of soil and dung.
• After 5-6 weeks, open the pit and show it to the residents of your colony. Also explain that their disposed off materials have been converted into compost manure.
• You can convince RWA (Resident Welfare Association) to use this manure for colony parks and also in plant pots kept in individual houses for beautification.

Question 6.
List the steps for preparing vermicompost.
Answer:

• Dig a pit about 30 cm deep or select a wooden box.
• Spread a net or chicken mesh at the bottom of pit or box. You can also spread 1 to 2 cm thick layer of sand.
• Spread some vegetable wastes including peels of fruits over the sand layer. You can use green leaves, husk or pieces of newspaper, dried stalks of plants and dried animal dung.
• Sprinkle some water to make the layer wet. Do not use excess of water. Press layer of leaves or waste so that it has sufficient air and moisture.
• Now, buy some redworms and put them in the pit.
• Cover them loosely with a gummy bag or an old sheet of cloth or a layer of grass.
• Redworms need food. So you can provide them as food- vegetable and fruit peels, coffee and tea remains and weeds from the field or garden. Bury this food about 2-3 cm inside the pit.
• Do not put salt, pickles, oil, vinegar, meat and milk preparations. This may cause growth of disease-causing organisms. Redworms do not survive in very hot or very cold surroundings.
• After 3-4 weeks, put some w^aste food in one corner of the pit. Most of the worms will shift towards newly added food.
• Remove the compost from the vacated part and dry it in the sun for a few hours. The vermicompost becomes ready for use.

Picture-Based Questions

Question 1.
Observe the given figures and answer the following questions.

a. Which of the above bins is used to dispose biodegradable waste?
b. Which of the above bins is used to dispose non-biodegradable waste?
Answer:
a. Green dustbin
b. Blue dustbin

Question 2.
a. Identify the organisms shown below.

b. What are these organisms used for?
Answer:
a. Redworms (earthworms),
b. These are used for making vermicompost.

These NCERT Solutions for Class 6 Science Chapter 15 Air Around Us Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Air Around Us NCERT Solutions for Class 6 Science Chapter 15

Class 6 Science Chapter 15 Air Around Us Textbook Exercise Questions and Answers

Question 1.
What is the composition of air?
Answer:
Air is mixture of nitrogen, oxygen, carbon dioxide, water vapour and a few other gases. Some dust particles may also be present in it. Air is a mixture of gases, mainly containing nitrogen (about 78% by volume) and oxygen (about 21% by volume). The remaining 1% is made up gases, such as argon (about 0.9%), carbon dioxide (0.03%) and small amounts of other gases. Varying quantities of dust, smoke and water vapour are also present. The amount of these in the air varies from place to place and from time to time.

Question 2.
Which gas in the atmosphere is essential for respiration?
Answer:
Oxygen gas in the atmosphere is essential for respiration.

Question 3.
How will you show that air supports burning?
Answer:
Fix two burning candles of same size in the middle of two troughs. Fill the troughs with equal amounts of water. The water level should be below the height of candles. Light the candles and cover one of them with a bigger jar and the other one with a smaller jar. Observe carefully what happens to the burning candles and the water level. Note the time after which both the candles go off. You will observe that the candle covered with smaller glass jar extinguishes first and then the one covered with the bigger jar. Water level rises up in both the jars. This shows that air is required for buming/combustion. Bigger glass jar had more air inside it, so the candle kept burning for a longer time. Oxygen in the jar is consumed due to burning. Hence, water level rises up to fill the empty space in the jar.

Question 4.
How will you show that air is dissolved in water?
Answer:
Take some water in a glass vessel or beaker. Heat it slowly on a tripod stand. Before the water begins to boil, look carefully at the inner surface of the vessel. You will see tiny bubbles on the inside. On heating, air dissolved in water escapes in the form of these bubbles. This shows that air is dissolved in water.

Question 5.
Why does a lump of cotton wool shrink in water?
Answer:
Cotton lump contains air in it. There are various spaces in which air is filled. When cotton lump is put into water, air present in the vacant space dissolves in water and cotton lump shrinks.

Question 6.
The layer of air around the earth is known as ……………
Answer:
Atmosphere.

Question 7.
The component of air used by green plants to make their food is …………….
Answer:
Carbon dioxide.

Question 8.
List five activities that are possible due to presence of air.
Answer:
The activities that are possible due to the presence of air are:

1. Rotation of windmills
2. Movement of sailing yachts
3. Flying of aeroplane, birds, etc.
4. Dispersal of seeds
5. Water cycle

Question 9.
How do plants and animals help each other in exchange of gases in the atmosphere?
Answer:
Animals and plants use oxygen from air during respiration and release carbon dioxide gas in air. But green plants release oxygen gas by using carbon dioxide during photosynthesis. Thus, we can say that animals and plants help each other in exchange of gases.

NCERT Extended Learning Activities And Projects

Question 1.
On a clear glass window facing towards an open area, fix a small rectangular strip of paper. Remove the strip after a few days. Do you notice a difference between the rectangular section that was left covered with paper and the rest of the glass window? By repeating this exercise every month, you can have an idea about the amount of dust present in air around you at different times of the year.
Hint:
Do it yourself.

Question 2.
Observe the leaves of trees, shrubs or bushes planted by the roadside. Note whether their leaves have some dust or soot deposited over them. Take similar observations with the leaves of trees in the school compound or in a garden. Is there any difference in deposition of soot on leaves of trees near the roadside? What could be the possible reasons for this difference? Take a map of your city or town and try to identify regions in the map where you have noticed very thick layer of soot on the plants by the roadside. Compare with results obtained by other classmates and mark these areas on the map. Perhaps the results from all the students could be summarised and reported in newspapers.
Hint:
Do it yourself.

Activity 1

Objective: To show the presence of air.
Materials required: Wind vane mounted on a stick.
Procedure

• Take a firki mounted on a stick.
• Hold it by its stick and move it in different directions in an open area.

Observation: The firki starts rotating.
Conclusion: The firki moves when the air strikes its blades. This shows that air is present around us.

• We all breathe in air. Breathing is an essential part of respiration. We breathe in oxygen rich air and breathe out carbon dioxide rich air.
• Components of Air: Air contains mostly nitrogen and oxygen. Nitrogen occupies 78% of the air. Oxygen occupies 21% of the air. 1% of the air is made up of carbon dioxide, other gases, water vapour, dust particles, etc.

i. Nitrogen

• It is the lightest, colourless, odourless gas. It is used to control combustion.
• It is used by plants and animals to synthesise proteins in the body.
• It cannot be directly used by plants or animals. It has to be fixed into its nitrate or nitrite forms. This is done by bacteria living in root nodules of legumes.
• It is used to manufacture fertilisers to increase soil fertility.
• It is used to manufacture ammonia used in many industries.
• Nitrogen prevents oxidation of stored food in packets.

ii. Oxygen

• It is a chemical element in the form of gas. Mostly it is diatomic, made up of two atoms. O₂ is the molecular oxygen.
• It is taken directly from the air by organisms living on land.
• It helps in oxidising the food eaten by organisms to release energy.
• Aquatic organisms take in oxygen dissolved in water.
• Oxygen is required for combustion.
• Oxygen in the form of ozone helps in the protection of living organisms from dangerous UV rays coming out from the sun.
• It is used as a fuel in rockets.
• It is stored in the cylinders and is used to artificial respiration to patients in the hospitals.

iii. Carbon dioxide

• It is the gas which is made up of one carbon atom combining with two atoms of oxygen (CO₂).
• It is used by plants in synthesising their food by the process of photosynthesis.
• It is used in fire extinguishers.
• It is used in storing soft drinks.

iv. Inert gases

• These are also called as noble gases. They occupy a negligible percentage in air.
• Argon is used to fill the bulbs to prevent their filament.
• Helium is used in providing low temperatures.
• Neon is used to fill special bulbs called as neon signs.
• Radon is used in treating cancer patients.

v. Water vapour

• It is a gaseous form of water present as gas in the air.
• Amount of water vapour in the air varies with sun’s heat.
• Hot sun can evaporate more amount of water and convert it into water vapour.
• It helps in the formation of clouds which later can come down as rain.

vi. Dust and smoke

• Air contains some amount of dust and smoke in it.
• Dust and smoke are contributed by vehicles and industries releasing them.
• These are harmful to human beings and can cause many respiratory diseases.

Activity 2

Objective: To show the presence of dust particles in air.
Materials Required: Black chart papers and black curtain.
Procedure:

• Close all the doors and windows with curtains pulled down to make the room dark.
• Now, open the door or a window facing the sun, just a little, in such a way that it allows sunlight to enter the room only through a slit.
• Look carefully at the incoming beam of sunlight.

Observation: We see a large number of tiny- shining particles moving in the beam of sunlight. These are the dust particles
Conclusion: Air contains dust particles.

Oxygen-Carbon dioxide Levels:
Oxygen and carbon dioxide levels in the air are maintained by different processes like respiration and photosynthesis.

Respiration involves utilisation of oxygen from air by living organisms and releasing carbon dioxide into it. It occurs in all living organisms. Photosynthesis involves utilisation of carbon dioxide from the air and release of oxygen into the air.

Hence, carbon dioxide is replenished by the process of respiration and oxygen is replenished by the process of photosynthesis.

Properties of Air

• Air is transparent.
• It is colourless. It is not visible.
• It can be felt when it moves. Moving air is called as wind.
• Air occupies space. Air is present everywhere.
• It can be displaced by water.
• Air exerts pressure.
• It can be compressed and filled into a container.

Activity 3

Objective: To show that a gas bottle which appears to be empty to us is actually filled with air.
Materials Required: An empty bottle and a bucket with water.

• Take an empty glass bottle. Turn it, upside down in a vessel of water.
• Now, dip the open mouth of the bottle into the bucket filled with water as shown in the figure (a) above. Observe the bottle.
• Now tilt the bottle slightly and observe again.

Observation: The water does not enter into the glass bottle because the bottle is filled with air. On tilting the bottle held in water, air present in the bottle goes out in the form of air bubbles. As the air from the bottle escapes, water starts entering the glass bottle.
Conclusion: A glass bottle appears to be empty to us in actually filled with air.

Other Uses of Air:

• Air is used to rotate wind mills, which can lift water.
• Wind energy is a renewable form of energy.
• It is also used to rotate wind mills which can generate electrical energy by aerogenerators.
• It is used in sail boats.
• It helps to scatter the seeds and pollens of flowers.
• It is used to inflate the tyres of vehicles.
• Nitrogen of air is used to manufacture fertilizers.
• Air is also used for winnowing.
• Birds, insects and bats can fly due to the presence of air.
• Air present in water supports aquatic life of various plants and animals. Similarly, air present in soil supports the survival of several organisms living in it.

Activity 4

Objective: To prove that fresh water contains dissolved air.
Materials Required: A glass beaker, a tripod stand and water.
Procedure:

• Take some water in a glass vessel or beaker.
• Heat it slowly on tripod stand.
• Well before the water begins to boil, look carefully at the inner surface of the vessel. Do you see tiny bubbles on the inside?
• These bubbles come from the air dissolved in water. When you heat the water, the air dissolved in it escapes. As you continue heating, the water itself turns into vapour and finally begins to boil.

Observation: We see the bubbles of air rising up in water.
Conclusions: The air dissolves slowly in fresh water. When the water is warmed, the solubility of air decreases and it comes out of water in the form of bubbles. Hence, water contains dissolved air.

Activity 5

Objective: To show that soil contains trapped air.
Materials Required: Glass beaker, a sample of soil.
Procedure:

• Take a lump of dry soil in a beaker or a glass.
• Add water to it and note what happens.

Observation:
When the water is poured on the lump of soil, it displaces the air which is seen in the form of bubbles.
Conclusion: Soil contains air trapped between its particles.

Class 6 Science Chapter 15 Air Around Us Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is the source of carbon dioxide in the air?
Answer:
Respiration by animals and plants and burning of fuels.

Question 2.
Mention one necessary condition for the combustion to take place.
Answer:
Presence of air.

Question 3.
Why is air considered as a mixture?
Answer:
Air contains oxygen and nitrogen as its major constituents of air. These gases retain their properties in air. So the air is called a mixture.

Question 4.
Name the major gas present in the (a) inhaled air (b) exhaled air.
Answer:
a. Oxygen
b. Carbon dioxide.

Question 5.
Name the major component of air.
Answer:
Nitrogen gas.

Question 6.
What is the source of oxygen gas in air?
Answer:
Photosynthesis by green plants is the source of oxygen gas in air.

Question 7.
What is the percentage of nitrogen in air?
Answer:
78.1%.

Question 8.
What is the percentage of oxygen in air?
Answer:
20.9%.

Question 9.
Name a device which uses wind energy to generate electricity.
Answer:
Windmills use the wind energy to convert wind energy into electrical energy.

Question 10.
Carbon dioxide is present to the extent of only 0.03% by volume in air. Why then is it considered to be so important?
Answer:
Air contains very little carbon dioxide – only 0.03%. However, it is a very crucial component of air as it is required by plants to make their food.

Question 11.
What is humidity?
Answer:
The amount of water vapour present in the air is known as humidity.

Short Answer Type Questions

Question 1.
Write four properties of air.
Answer:
Properties of air:

• Air is invisible.
• Air occupies space.
• Air is transparent and colourless.
• Air exerts pressure.

Question 2.
During an incident of fire, one is advised to wrap a woollen blanket over a burning object. Explain why?
Answer:
During an incident of fire, one is advised to wrap a woollen blanket over a burning object because air gaps in woollen blanket act as an insulating medium which cuts the supply of oxygen to the object that is burning, thereby prevent it from further burning.

Question 3.
What is wind energy? Write its two advantages.
Answer:
Wind energy is a form of renewable energy produced through machines that use movement of wind as their power source.

Two advantages:

1. Wind is a free and infinite resource.
2. Wind is a clean energy source.

Question 4.
What are the activities which can be possible only in the presence of air?
Answer:
Activities which can be possible only in the presence of air are:

• Photosynthesis
• Burning
• Respiration
• Generation of electricity by windmills
• Sailing of ship
• Seed dispersal

Question 5.
What happens if the percentage of carbon-dioxide increases in the air?
Answer:
The increased percentage of carbon- dioxide will cause green house effect, i.e., it will not allow the hot rays of sun to escape from the atmosphere, after reflection, once they enter. It will lead to global warming.

Question 6.
Why do we see the sky and air clear and clean after rainfall?
Answer:
This is because the dust particles which remain suspended in air get loaded and come down on the ground due to rainfall. This is the reason that the sky and the air look clean and clear after rainfall.

Question 7.
Explain why mountaineers carry oxygen cylinders with them?
Answer:
As you go up above the sea-level, the atmospheric pressure goes on decreasing and the amount of oxygen also decreases at higher altitude.

Question 8.
What is the importance of the ozone layer in the atmosphere?
Answer:
The upper atmosphere contains a layer of gas called ozone. It prevents harmful rays of the sun from reaching the earth. These rays, called ultraviolet rays, can cause eye problems and skin cancer.

Question 9.
How do fish breathe?
Answer:
Fishes breath in oxygen dissolved in water. Fishes have organs called gills that help to use oxygen dissolved in the water.

Question 10.
How is nitrogen obtained by plants?
Answer:
Nitrogen is required by plants for their growth. But plants are not able to absorb the nitrogen directly from the air. Nitrogen in the air is brought to the earth in the form of nitric acid through lightning and rain. Microbes in soil change it to nitrate compounds which are absorbed by the plants. Also, nitrogen in the air is used by us to manufacture fertilisers. These fertilisers again provide the essential nitrogen to plants.

Long Answer Type Questions

Question 1.
How do you prove that air occupies space?
Answer:
The following activity proves that air occupies space.
Take an empty glass bottle. Turn it upside down. Now, dip the open mouth of the bottle into the bucket filled with water. Water does not enter the bottle. Now tilt the bottle slightly. Now water enters the bottle and we see bubbles coming out of the bottle.

The bottle was not empty at all. In fact, it was filled completely with air even when we turned it upside down. That is why water does not enter the bottle when it is in an inverted position, as there was no space for air to escape. When the bottle was tilted, the air was able to come out in the form of bubbles and water filled up the empty space that the air has occupied.

Question 2.
How does the atmosphere help to maintain the right temperature on the earth?
Answer:
The atmosphere helps to maintain the right temperature on the earth. The heat and light of the sun fall on the earth’s atmosphere. Some of it is absorbed by the atmosphere, while the rest is reflected back. This prevents the earth from becoming very hot during the day. At night, the trapped heat in the atmosphere prevents the earth from cooling down too much. The atmosphere, thus, acts like a blanket around the earth and helps to keep the earth’s surface at the right temperature for life to exist.

Question 3.
Define pollution. How does air get polluted?
Answer:
The addition of unwanted substances in the environment in quantities that are harmful to living beings is called pollution. Air is getting polluted day by day because of various human activities as given below:
a. Burning of fuels like coal and petroleum. Excessive burning of fuels like wood, smoke, etc.
b. Harmful gases released from industries.
c. Smoke released by vehicles and machines releasing gases are the major causes of air pollution. These gases spread and mix in the air and spoil the quality if air, thereby making it impure.

Question 4.
List the uses of air.
Question
Besides breathing, air is useful to us in many other ways.

• The wind makes windmills rotate. The windmills are used to draw water from tube wells and run flour mills. They are now being widely used to generate electricity.
• Aeroplanes, helicopters, balloons, parachutes and yachts work because of air.
• Birds, insects and bats are able to fly because of the presence of air.
• Air helps in the dispersal of seeds.
• Air helps in pollination of several flowers.
• Air plays an important role in the water cycle.

Question 5.
Demonstrate through a simple experiment that the air mainly contains nitrogen and oxygen in the volume ratio of 4 : 1.
Answer:
Aim of experiment: To show that air contains nitrogen and oxygen in the ratio 4 : 1 by volume:

Procedure: Take a glass container and fix a candle at its centre. Put some quantity of water in the container. Place an empty, dry gas jar over it. Mark five marks above water surface on the jar at equal distances.

The candle is lightened and is covered with the gas jar. After some time, the candle is extinguished and the water level is raised in gas jar. The raised level in water is 1/5 of the volume of air in the gas jar. This proves that one part of the air of the jar is a gas which supports combustion, i.e., oxygen. Hence, 1/5 by volume is oxygen in air. Rest in mainly nitrogen.

Picture-Based Questions

Question 1.
a. What does the following pie chart represent?

b. Which gas forms the major part of the chart?
Answer:
a. It represents the composition of air.
b. Nitrogen gas (78%).

Question 2.
Observe the figure and answer the following questions.

a. What does it represent?
b. In which case is air escaping out from bottle?
Answer:
a. It represents that air occupies space.
b. In case II.

These NCERT Solutions for Class 6 Science Chapter 14 Water Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Water NCERT Solutions for Class 6 Science Chapter 14

Class 6 Science Chapter 14 Water Textbook Exercise Questions and Answers

Question 1.
Fill up the blanks in the following:
a. The process of changing of water into its vapour is called ……………..
b. The process of changing water vapour into water is called ……………..
c. No rainfall for a year or more may lead to …………….. in that region.
d. Excessive rains may cause ……………..
Answer:
a. evaporation or vaporisation
b. condensation
c. drought
d. flood

Question 2.
State for each of the following due to evaporation or condensation:
a. Water drops are formed on the outer surface of the bottle or any container containing cold water.
b. Formation of steam from wet clothes while they are ironed.
c. Appearance of fog on a cold winter morning.
d. Wiping of blackboard dries it up.
e. Steam rising from a hot girdle when water is sprinkled on it.
Answer:
a. Condensation
b. Evaporation
c. Condensation
d. Evaporation
e. Evaporation

Question 3.
Which of the following statements are “true”?
a. Only during the monsoon season, the water vapour is present in the air.
b. Water vapourises into steam only from oceans, lakes and rivers but not from the soil.
c. The process of converting water into its vapour is called evaporation.
d. The process of evaporation takes place only in sunlight.
e. The water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.
Answer:
a. False
b. False
c. True
d. False
e. True

Question 4.
Suppose you want to dry your school uniform quickly. Would spreading it near an angithi or heater help? If yes, how?
Answer:
Yes, in order to dry the uniform faster, the uniform is spread near a heater since the rate of evaporation is faster at higher temperatures. The rate of evaporation is directly proportional to temperature. So, the uniform will be dried up quickly.

Question 5.
Take out a cooled bottle of water from refrigerator and place it on a table. After some time, you will notice a puddle of water around the bottle on the table. Why?
Answer:
Since the water bottle is at a very low temperature, the surface exposed is also very cold. As the cool surface is exposed, condensation of water vapour present in the air occurs. Now, the condensed water molecules spread around the bottle. So a puddle of water is noticed after some time.

Question 6.
To clean our spectacles, we often breathe out hot air on glasses to make them wet. Explain why the glasses become wet?
Answer:
The air we blow out contains water vapour. The water vapour condenses on the spectacles forming moisture and the glass is coated with a layer of minute water droplets. With the addition of small amount of water, we can easily clean the spectacles.

Question 7.
How are clouds formed?
Answer:
The water present on the earth’s surface evaporates due to heat radiated by the sun. The water vapour present in the air condenses to form tiny droplets of water at high altitudes which in large quantity looks as clouds. Thus, clouds are formed by the condensation of water vapours available in the air at high altitudes.

Question 8.
When does a drought occur?
Answer:
When there is no rainfall for many years over a long period of time then there will arise a scarcity of water in that locality or region. This leads to drought.

NCERT Extended Learning Activities and Projects

Question 1.
List three activities in which you can save water. For each activity describe how you would do it.
Hint:
We can save water by rainwater harvesting, using pre-used water for watering plants and preventing water pollution in rivers, lakes, etc.

Question 2.
Collect pictures relating to floods or droughts from old magazines or newspapers. Paste them in your notebook and write about the problems that people would have faced.
Hint:
Do it yourself.

Question 3.
Prepare a poster on ways of saving water and display it on your school notice board.
Hint:
Do it yourself.

Question 4.
Write a few slogans of your own on the topic ‘Save Water’.
Hint:
Do it yourself.

Question 5.
Can the interlinking of rivers be a solution for mitigation of flood? Discuss.
Hint:
Yes, it can help in mitigation of flood as the excess water will distribute over a larger area leading to better maintenance of water levels during heavy rainfalls.

Activity 1

Objective: To estimate how much water do we need for our daily activities.
Procedure:

• List all the activities for which you use water in a day.
• Measure the amount of water used for each activity by all the members of your family in a day.

Observations: Estimation of the amount of water used by a family in a day:

Conclusion: A family of four requires about 502 litres of water per day.

Sources of Water: Ponds, wells, streams, lakes and rivers are the different sources of drinking water. Drinking water is called as potable water. Oceans and seas supply water to other water bodies through water cycle.

States of Water: Water exists in three different states.
i. Water can occur in the solid state. Solid state can be represented by ice, snow or hail.
ii. Water can occur in the liquid state. Liquid state of water can be represented by river, rain or sea.
iii. Water can occur in the gaseous state. Gaseous state of water can be represented by water vapour.

Three states of water are inter-convertible
i. Solid form of water can be converted into liquid form by heating. This is called melting.
ii. Liquid form of water can be converted into gaseous form by heating. This is called vapourisation or evaporation.

iii. Gaseous form can be converted into liquid form by cooling and the process is called condensation.
iv. Liquid form can be converted into solid form by freezing.

Water cycle: The cyclic movement of water from the atmosphere to the Earth and back to the atmosphere through various processes is called as water cycle. Different steps of water cycle include evaporation, transpiration, condensation, precipitation and surface run-off.

i. Evaporation: The water present on the surface of oceans evaporates by the sun’s heat. This process of conversion of water from liquid state to vapour state is called evaporation. Evaporation also takes place from wet clothes, fields, ponds, lakes and rivers.

Activity 2

Objective: To show that evaporation of water occurs in sunshine as well as in shade but it is faster in sunshine.
Materials required: Two similar plates and water.
Procedure:

• Take two similar plates.
• Place one of the plates in sunlight and keep the other under shade.
• Now, pour equal amount of water in each of the plates. You can use a cap of a bottle to measure water.
• Make sure that water does not spill over.
• Observe the two plates after every 15 minutes.

Observations: Water kept in sunlight evaporates faster than that kept in shade.
Conclusion: In sunlight, evaporation takes place faster because sunlight produces a higher temperature. In shade, evaporation takes place slower because of lower temperature in shade. Evaporation takes place continuously from all the open surfaces of water at all temperatures.

ii. Transpiration: Plants take in water from the soil to prepare their own food and also for other life processes. They release excess water into air through leaves in the form of water vapour by the process of transpiration.

iii. Condensation: The evaporated water is carried away by warm air. As the warm air moves higher from the surface of the Earth, it starts to cool down. This water vapour condenses to form tiny water droplets which float in air to form clouds or fog.

iv. Precipitation: When droplets of water present in clouds unite to form large sized drops of water, being heavy, they begin to fall. This falling of water drops from clouds is called precipitation. Precipitation may occur in the form of:

• Rain: If water droplets fall in form of liquid on the surface of the earth, it is called rain.
• Hail or snow: Precipitation may be in the form of frozen or solid form. If the size of frozen water drops is large, the precipitation is called as hail. If precipitation is in the form of light flakes, it is called snow.
• Dew: Water droplets, especially during winter nights, formed by water vapour present in the air, are called as dew.

Activity 3

Objective: To study how are clouds formed.
Materials Required: Glass and ice cubes.
Procedure:

• Take a glass half filled with water.
• Wipe the glass from the outside with a clean piece of cloth.
• Add some ice into the water. Wait for one or two minutes.
• Observe the changes that take place on the outer surface of the glass.

Drops of water appear on outer surface of the glass containing water with ice
Observations: The puff of air around the glass becomes hazy/cloudy. This is the cloud formed.
Conclusion: The cold surface of the glass containing ice water cools the air around it, and the water vapour of the air condenses on the surface of the glass.

v. Surface run-off: Some amount of rainwater is absorbed by the soil and settles down as groundwater. Most of the rainwater flows down the hills and mountains to collect into rivers, lakes or streams. Rain also washes away the topmost layer of the soil into water bodies.

Importance of water cycle in nature

• Water cycle makes fresh water available in the form of rains.
• Water cycle keeps the amount of water on the earth’s surface constant. This is because the water removed from the earth during evaporation is put back to earth during rain and snowfall.
• Water cycle plays an important role in regulating weather.

Groundwater: The water that seeps into the ground and gets accumulated there is known as groundwater. Groundwater is the source of water in wells and lakes. Groundwater is withdrawn through hand pumps and tube wells.

Flood: Floods are caused by rise in the water level in ponds and lakes due to heavy rainfall. The excess rain water flows on to the land causing floods. Floods make the soil water-logged. Floods affect normal life by disturbing everything which comes in its way. Floods wash out the living beings such as plants, fish, other animals, etc. Floods cause heavy loss to human life. Floods cause uprooting of trees. They wash away the crops. They result in shortage of food supply.

Droughts: Droughts are the conditions which involve abnormally long period of insufficient or no rainfall. Droughts are caused due to lack of rains. Drought condition results in drying up of wells, lakes, ponds and thereby creating water scarcity. Droughts result in the evaporation of water from the soil leaving the soil dry and patchy.

Effects of droughts

• Droughts result in mass death of plants and animals due to dehydration.
• It affects agriculture and lessen food production.
• It results in the death of animals and birds which provide us animal products like milk, meat and eggs. This scarcity of food results in the famine.
• Droughts result in forest fires caused by enormous amount of heat from scorching sun.

Water Conservation: Water is an essential natural resource. There exists no life without water. Water is so precious that it has to be conserved. Avoiding water wastage is also a kind of water conservation. Conservation programmes can be successful, if all people follow them faithfully.

How to Conserve Water: Excess rainwater running in the rivers is stored in huge and special structure called as dams. Dams are huge structures built on rivers to hold back excess water. Dams prevent areas from flooding by storing large amount of water. Dams provide water for irrigating fields, domestic use and also drinking water for some areas.

Drinking water should not be wasted to water the plants. Water bodies should not be polluted in order to get pure water. Water should not be wasted during irrigation of fields. Modem methods like spraying, sprinkling or drip irrigation should be used. Water should be used judiciously to avoid wastage. Destruction of trees should be controlled to increase the rainfall.

Rainwater harvesting: Rainwater harvesting includes collection and storing of rainwater from the roofs of houses and huge constructions. This is also called as rooftop rainwater harvesting. Constant use of freshwater from the ground results in water scarcity. Rainwater harvesting increases the level of underground water.

Technique involved in rainwater harvesting:

• Rainwater is collected at the rooftop.
• It is allowed to flow into pipes.
• It is filtered through wire mesh.
• It is allowed to pour into an underground tank setup to store rainwater. These tanks contain layers of sand, gravel, charcoal that will filter the dirt and other impurities from rainwater. This water seeps back into the ground slowly to increase the level of groundwater table.
• Second technique of rain water harvesting is to allow rainwater to go into the ground directly from the roadside drains.

Class 6 Science Chapter 14 Water Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
Name two processes which are responsible for the formation of clouds.
Answer:
Evaporation and transpiration.

Question 2.
What happens to plants when they are not watered?
Answer:
If plants are not watered, they would wither. The seeds would not germinate and plants would not grow well.

Question 3.
Explain what you mean by evaporation.
Answer:
The process of changing water (liquid form) into water vapour (gaseous form) is called evaporation.

Question 4.
What happens to the potted trees when they are over watered? Why?
Answer:
Water logging takes place and the plant may die as roots are unable to take oxygen from the soil.

Question 5.
What would have been the consequence if the water was not recycled in nature by the water cycle?
Answer:
There would be no water available for use. Most of the natural phenomenon would be affected.

Question 6.
Why we rarely notice water vapour from a bucket full of water?
Answer:
We rarely notice water vapour from a bucket full of water because evaporation of water is a very slow process.

Question 7.
Why does a mist of tiny water droplets form when we breathe out on a window in winter?
Answer:
When our warm breath touches a cold window, it condenses and forms a mist of tiny water droplets.

Question 8.
In which forms does water exist on the earth?
Answer:
Water exists on the earth in all the three physical forms: ice (solid), water (liquid) and water vapour (gas).

Question 9.
How is snow or hail formed?
Answer:
When water droplets freeze in the air and begin to fall, it is called hail or snow.

Question 10.
What is precipitation?
Answer:
When water drops come together in the air and become heavy, they begin to fall. This falling of water drops is called precipitation.

Question 11.
What is the importance of convertibility of water from one state to another state?
Answer:
The easy convertibility of water from one state to another state makes its availability in all parts of the earth and throughout the year.

Short Answer Type Questions

Question 1.
What are the two main functions of water for living organisms?
Answer:
The two main functions of water for living organisms are:

1. Water is very essential for the growth of plants, germination of seeds and in photosynthesis process.
2. Water is also very essential for the transportation of goods and people.

Question 2.
Why is sea water not used for domestic use?
Answer:
Sea and ocean water contains huge amounts of different types of salts. Because of the presence of these salts, the ocean water is salty and cannot be used for any domestic purpose such as drinking, washing and for irrigation purposes. So, only water from lakes, rivers, ponds and rainwater harvesting are used for domestic purposes.

Question 3.
Why does the water which is spilt on the floor disappear after a period of time?
Answer:
Due to the process of evaporation, the water spilt on the floor is converted into water vapour. So it disappears after a period of time.

Question 4.
How does heavy rain affect us?
Answer:
Heavy rains may cause:

• rise of water level in reservoirs, rivers, pond, lakes, etc.,
• water logging in household areas,
• floods causing drastic damage to crops, property and animals.

Question 5.
How does the failure of rainfall affect people on the earth?
Answer:
The failure of rainfall can cause the following:

• The soil in that region becomes dry and may lead to drought.
• Water level in rivers, lakes, dams, etc., may fall below the minimum level, ponds and canals may even dry up. This results in people of that region having no access to water for even their basic needs.
• The ground water level will also fall.

Question 6.
There are 4 containers A, B, C and D with the same quantity of water in each of them. Answer the following questions based on these figures.

a. Identify in which container does the water evaporates faster than the rest?
b. Identify in which container the water evaporates at the slowest rate. Justify your answer.
Answer:
a. C – More the exposed surface area, more will be the rate of evaporation,
b. B – Since it is closed, evaporation will not take place.

Question 7.
Why do we see more fog in areas where there are a lot of trees during winter season?
Answer:
Due to the presence of a lot of trees, air at that region will have more water vapour than compared to cities or other regions. These water vapours tend to condense on smoke or dust particles which leads to the formation of thick fog.

Question 8.
What is the difference between fog and clouds?
Answer:
Clouds can form at many different altitudes. They can be as high as 12 miles above sea level or as low as the ground. Fog is a kind of cloud that touches the ground. Fog forms when the air near the ground cools enough to turn its water vapour into liquid water or ice.

Question 9.
What happens when there is a lot of rainfall?
Answer:
When it rains excessively, water gets collected here and there, causing disruption of normal life. The water levels of rivers, lakes and ponds rise. When it exceeds a certain maximum level, the water reservoirs cause floods. Crops, fields, villages and low-lying areas get submerged underwater. During floods, many animals living in water get trapped on land and die when the flood water recedes. Heavy rains also kill the animals living in soil because such animals do not get air to breathe when all the soil gets covered with floodwater.

Long Answer Type Questions

Question 1.
What ¡s meant by rainwater harvesting? Explain the different methods involved in rainwater harvesting.
Answer:
Rainwater harvesting is the process of collecting the rainwater and storing it in tanks, ponds, lakes, etc. In this process, rainwater in collected from the rooftops of houses or buildings with the help of pipes into a tank for storage purpose and can be used at a later point of time.

Methods involved in rainwater harvesting:

• Rooftop rainwater harvesting: In this structure, the rainwater from the rooftop is collected into a storage tank, employing pipes to collect and transfer.
• In another method, a huge pit is dug at close proximity to the house for collecting the rainwater. This pit is stuffed with different layers of coarse gravels, bricks and granite or sand pieces to filter rainwater.

Question 2.
What ¡s a water cycle? Describe the water cycle in nature. Also, draw a labelled sketch to show the water cycle in nature.
Answer:
Water keeps on circulating in nature.
Although we use water for different activities, the amount of water remains the same on the earth’s crust. This is maintained by the water cycle. The cyclic pattern in which water keeps moving from the oceans and seas to the sky as water vapour, from the sky to the land as rain or snow and from land to the oceans and seas is known as the water cycle.

Question 3.
Write down the advantages and disadvantages of dams.
Answer:
Advantages:

1. It stores water and provides water for irrigation.
2. It leads to prevention of flooding because the water does not enter in the rivers in large quantities.
3. It is used to generate electricity. The electricity generated by water in dams is called hydroelectricity.

Disadvantages:

1. They can be constructed on limited sites.
2. It affects aquatic life, plants and animals.
3. The building of dams requires relocating population living in that area.

Question 4.
What are the problems faced by the people living in areas having drought conditions?
Answer:
Some of the problems faced by the people because of drought in an area are as follows:

• In drought conditions, the soil does not have sufficient moisture to grow crops well. Since the crop plants do not grow well, drought leads to severe shortage of food for the people in that region.
• In drought conditions, the vegetation such as grass and other fodder does not grow well and leads to shortage of fodder for the domestic animals like cows and buffaloes.
• Due to shortage of food and fodder, many people living in drought affected areas even migrate to other places along with their domestic animals in search of food and fodder. Some people and domestic animals may even die of starvation.

Question 5.
Explain the formation of (a) fog and (b) dew.
Answer:
a. Formation of fog: During winter, sometimes, condensation of water vapours starts near the surface of earth. These clouds of condensed vapour do not become water drops and do not rain. In fact these appear near the earth’s surface as fog.

b. Formation of dew: During winter nights, when air becomes very cool, the vapours present near earth’s surface condense and water droplets are formed. These appear as dew. This dew could be observed on railings, leaves and flowers in the winter mornings.

Picture-Based Questions

Question 1.
a. Identify the following states of water.

b. By which process can B be converted to A?
c. By which process can C be converted to A?
Answer:
a. A – Liquid water; B – Solid ice; C – Water vapour.
b. Melting
c. Condensation.

Question 2.
a. Name the process shown below.

b. What does the above image depict?
Answer:
a. Evaporation
b. Evaporation takes place faster in sunlight than in shade.

These NCERT Solutions for Class 6 Science Chapter 13 Fun with Magnets Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.

Fun with Magnets NCERT Solutions for Class 6 Science Chapter 13

Class 6 Science Chapter 13 Fun with Magnets Textbook Exercise Questions and Answers

Question 1.
Fill in the blanks in the following:
a. Artificial magnets are made in different shapes such as ……………., …………… and …………….
b. The materials which are attracted towards a magnet are called ……………..
c. Paper is not a …………….. material.
d. In olden days, sailors used to find direction by suspending a piece of ……………..
e. A magnet always has …………….. poles.
Answer:
a. bar magnet, horse-shoe magnet and cylindrical magnet
b. magnetic materials
c. magnetic
d. lodestone
e. two

Question 2.
State whether the following statements are true or false:
a. A cylindrical magnet has only one pole.
b. Natural magnets were discovered in Greece.
c. Similar poles of a magnet repel each other.
d. Maximum iron fillings stick in the middle of a bar magnet when it is brought near them.
e. Bar magnets always point towards North-South direction when suspended freely in air.
f. A compass can be used to find East-West direction at any place.
g. Rubber is a magnetic material.
Answer:
a. False
b. True
c. True
d. False
e. True
f. True

Question 3.
It was observed that a pencil sharpener gets attracted by both the poles of a magnet although its body is made of plastic. Name a material that might have been used to make some part of it.
Answer:
The blade of a pencil sharpener is made of iron. Since iron is a magnetic material, hence pencil sharpener is attracted towards a magnet.

Question 4.
Column I shows different positions in which one pole of a magnet is placed near that of the other. Column II indicates the resulting action between them for each situation. Fill in the blanks.

Answer:

Question 5.
Write any two properties of a magnet.
Answer:
Two properties of magnet are as follows:

1. A magnet always points in north-south direction, if suspended freely.
2. A magnet always has two poles.

Question 6.
Where are poles of a bar magnet located?
Answer:
At the two ends.

Question 7.
A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole located?
Answer:
For this, we need to take following steps:

• Tie the bar magnet with a string and suspend it with a horizontal support.
• Allow the magnet to come to rest.
• Mark the end which points to the north, as north pole.
• Repeat the above steps two more times to confirm.

Question 8.
You are given an iron strip. How will you make it into a magnet?
Answer:
For this, you need to place the iron strip on a flat surface. Now take a bar magnet and place one of its poles near the edge of the strip of iron. Without lifting it, move it along the length of the iron strip till you reach the other end. Now lift the magnet and bring the pole to the same point of strip from where you began. Repeat this process about 30-40 times. Bring some iron fillings near the strip and observe that the strip attracts the filings. This indicates that the iron strip has become a magnet.

Remember that the pole of magnet and direction of its movement should not be changed.

Question 9.
How is a compass used to find directions?
Answer:
The working of a compass is based on the property of a magnet to stay in north-south direction. This is a small glass case containing a magnetised needle pivoted on a nail. The needle can rotate freely. Whenever it is kept, its needle always rests in north-south direction.

Normally the north pole of the needle is painted red or some other indication is given to identity north and south poles. So using this needle, north and south directions can be identified.

Question 10.
A magnet was brought from different directions towards a toy boat that has been floating in water in a tub. Effect observed in each case is stated in Column I. Possible reasons for the observed effects are mentioned in Column FI. Match the statements given in Column 1 with those in Column II.

Answer:
1. (d),
2. (e),
3. (b),
4. (a),
5. (c).

NCERT Extended Learning Activities and Projects

Question 1.
Using a compass, find the direction in which windows and entrance to your house or classroom open.
Hint:
Do it yourself.

Question 2.
Try to place two equal sized bar magnets one above the other such that their north poles are on the same side. Note what happens and write your observations in your notebook.
Hint:
Do it yourself.

Question 3.
Few iron nails and screws got mixed with the wooden shavings while a carpenter was working with them. How can you help him in getting the nails and screws back from the scrap without wasting his time in searching with his hands?
Hint:
We can suspend and rotate a magnet inside the mixture. All the iron nails and screws will get stick to it and separate from the mixture.

Question 4.
You can make an intelligent doll, which picks up the things it likes (Fig. 13.17 on NCERT). Take a doll and attach a small magnet in one of its hands. Cover this hand with small gloves so that the magnet is not visible. Now, your intelligent doll is ready. Ask your friends to bring different objects near the doll’s hand. Knowing the material of the object you can tell in advance whether the doll would catch it or not.
Hint:
Do it yourself.

Activity 1

Aim: To identify the materials which are attracted by magnet and not attracted by the magnet.
Materials Required: A small bar magnet and waste materials from your house or school.
Procedure:

• Fix a small bar magnet to a wooden stick.
• Move this magnet stick over the dry wastes from different places such as office, home, etc., and record your observations.

Observations:

Conclusion

• Iron, steel, cobalt, nickel and their alloys are magnetic substances which are attracted by a magnet.
• Aluminium, copper, brass, stainless steel, wood, leather and plastic are non-magnetic substances which are not attracted by a magnet.

Poles of a Magnet: A magnet has two poles, viz, North Pole and South Pole. The magnetic power is concentrated on the poles of a magnet. When a bar magnet is suspended to move freely, it always points in the north-south direction. The north pole of the magnet points towards the geographical north and the south pole of the magnet points towards the geographical south.

Activity 2

Aim: To show that a magnet always comes to rest in a fixed direction.
Materials Required: Bar magnet and wooden stand.
Procedure:

• Mark one end of a magnet for identification.
• Hang it from a wooden stand with the help of a thread.
• Allow it to come to rest.
• Mark the direction in which the magnet comes to rest on the ground.
• Now rotate the magnet and observe the direction in which it comes to rest again.

Observations: The magnet always comes to rest in the same direction. The direction is found to be north-south direction.
Conclusion: A freely suspended bar magnet always comes to rest in a particular direction, which is the North-South direction.

Interaction between poles of Magnet

i. Like poles repel each other: This means when north pole of a magnet is brought near the north pole of another magnet, both repel each other. The same holds true for the south poles of two magnets.
ii. Unlike poles attract each other: This means when north pole of a magnet is brought near the south pole of another magnet, both attract each other.

Lodestone: The magnetic stone indicating directions used by sailors in olden days to identify directions is called lodestone.
Strength of a magnet
i. The strength of a magnet is maximum at its poles.
ii. The strength of magnet decreases as we go towards the mid-point of a magnet.
iii. The strength of a magnet is very less or zero at the mid-point of a magnet. It is called neutral point.

Activity 3

Aim: To show that magnetic force is maximum at the ends of a magnet.
Materials Required: Bar magnets and iron filings.
Procedure:

• Hold a bar magnet and try to stick iron filings across its length and then at its poles.
• Observe the number of iron filings which stick to the magnet as we go from centre towards its poles.

Observations: More number of iron filings stick to the ends of the magnet than at its centre.
Conclusion: The magnetic force is maximum at the ends or poles of the magnet.

• Temporary magnets: They retain their magnetic properties only for a short time. They are usually made up of iron, nickel and cobalt. These materials behave like magnets only when they are brought closer to another strong magnet.
• Permanent magnets: They retain their magnetic properties for a very long period of time. They are usually made up of an alloy containing one or more of the three elements: iron, nickel and cobalt.
• Demagnetisation: The process of destroying the magnetic properties of a magnet is called demagnetisation.
• SeIf-demagnetisation: When two poles of a magnet are left free, the magnet loses its magnetism slowly. This is called self demagnetisation.
• Care of magnets: To avoid self demagnetisation, magnets are kept in such a way that their opposite poles are joined. This is done by placing soft iron pieces (called keepers) across both the ends. A wooden piece may be kept in between the two bar magnets.

Compass: The small glass case containing a magnetised needle pivoted on a nail in it is called compass. The needle rotates freely and stops in north-south direction. It is used to find directions.

Activity 4

Aim: To make a simple magnetic compass.
Materials Required: A sticker showing all directions, cork and a magnetised needle.
Procedure:

• Pass the magnetised needle through the cork.
• Float it in a trough filled with water, such that the needle is above water.
• Mark the positions (N and S) when it comes to rest.
• Stick the sticker with N and S on it exactly at the place where N and S are marked on the cork. Magnet compass is ready to use.

Observations: This is a simple magnetic compass that always points in north-south direction.

Class 6 Science Chapter 13 Fun with Magnets Additional Important Questions and Answers

Very Short Answer Type Questions

Question 1.
What is a magnet?
Answer:
A magnet is an object which attracts things made of iron, steel, nickel and cobalt.

Question 2.
What happens when N-pole of a magnet is brought near the N-pole of a suspended magnet?
Answer:
There is repulsion between these two magnets as there is repulsion between like poles.

Question 3.
At which place on a magnet, its magnetic force is maximum?
Answer:
At poles.

Question 4.
In which direction does a suspended magnet come to rest?
Answer:
Magnet comes to rest in N-S (north-south) direction.

Question 5.
Name the compound of iron contained in lodestone.
Answer:
The compound of iron is iron oxide or magnetite.

Question 6.
Name the shepherd after which magnet was named.
Answer:
Magnes.

Question 7.
How can you separate a magnetic substance from a mixture?
Answer:
By using a bar magnet, the magnetic substance can be separated from a mixture.

Question 8.
Name a natural material which acts like a magnet.
Answer:
Magnetite.

Question 9.
Can we have an isolated north or South Pole?
Answer:
We cannot have an isolated north pole or south pole. They always exist in pairs.

Question 10.
What are magnetic materials?
Answer:
Materials that get attracted to a magnet are called magnetic materials.

Question 11.
What are non-magnetic materials?
Answer:
Materials that do not get attracted to magnets are called non-magnetic materials.

Question 12.
Define magnetic poles.
Answer:
The regions of a magnet where the force of magnet is the strongest are called poles of the magnet.

Question 13.
What type of magnet is used in an electric bell?
Answer:
U-shaped magnet is used in electric bell.

Question 14.
Name an instrument which is used to find directions.
Answer:
Magnetic Compass.

Short Answer Type Questions

Question 1.
How can a magnet be demagnetised?
Answer:
A magnet can be demagnetised by heating, hammering or dropping from some height.

Question 2.
How can you tell whether a particular substance is magnetic or non-magnetic?
Answer:
If a particular substance is attracted towards a magnet, then it is a magnetic substance and if it is not attracted towards a magnet, then it is a non-magnetic substance.

Question 3.
Why should we not keep magnets near mobiles, television, computers and CDs?
Answer:
Devices such as mobiles, television, computers and CDs are made up of magnetic materials and have magnets in them. If we keep magnets near them, magnet may spoil these devices.

Question 4.
Why is a magnet called a ‘magnetic dipole’?
Answer:
Even a smallest piece of a magnet has north and south poles and we cannot separate the two poles. Therefore, poles always exist in pairs. That is why a magnet is called a “magnetic dipole”.

Question 5.
What are electromagnets?
Answer:
Electromagnet is a magnet made by passing electric current through a soft metal surrounded by a coil. The magnetic field disappears when the current is turned off. It is hence, a temporary magnet.

Question 6.
If a bar magnet broke into pieces, then where will its north and south poles occur?
Answer:
Each piece has a north and south pole. Or, we can say, that the end that was pointing south will be the south pole and its opposite end will be the new north pole.

Question 7.
It is said that repulsion is a sure test for magnetism. Why is it so?
Answer:
To identify the magnet, repulsion (like poles of two magnets repel) is the only test which will let you know whether the given material is a magnet or not. This is because both poles of a magnet can attract a magnetic object but only two magnets can repel each other.

Question 8.
You are given two rods. Out of these, one is an iron rod and the other one is a magnet, how will you identify these rods?
Answer:
Take both the rods and suspend them separately. Bring one end of a bar magnet close to both the ends of the suspended rod. If it shows attraction at both the ends then it is an iron rod. If it shows attraction at one end and repulsion at the other end, then it is a bar magnet.

Question 9.
Write main properties of a magnet.
Answer:

• Magnet has two poles—South Pole and North Pole.
• Poles of a magnet cannot be isolated.
• Like poles repel each other and unlike poles attract each other.

Long Answer Type Questions

Question 1.
Name and describe the instrument that uses a magnet to find direction.
Answer:
The instrument that uses a magnet to find direction is a magnetic compass. This magnet consists of a magnetised needle pivoted at a point so that it can move freely. We have to rotate it till the north of the needle matches the north of the scale.

Question 2.
List any three uses of a magnet.
Answer:
The three uses of magnet are:

1. In credit cards and ATM cards where information is stored in a magnetic strip.
2. In audio and video tapes and computer hard disks to store information.
3. In refrigerator door stickers, closing mechanism of refrigerator doors, bulletin boards and toys.
4. Fridge magnets.

Question 3.
Given a bar magnet, how will you find west direction?
Answer:
To find west direction with a bar magnet, we will tie the magnet and leave it freely as a freely suspended magnet aligns itself in north-south direction. As it is free and is tied using a copper wire stirrup, slowly its north pole will itself move towards the geographical north and we can locate the west.

Question 4.
A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole located?
Answer:
Take the bar magnet and suspend it freely with the help of a thread. The end that points towards north pole will be regarded as north end of the magnet. Take a bar magnet with known/marked poles on it. Let the north pole of the magnet be brought closer to the suspended magnet at the end that is pointing towards north, if it shows repulsion, then it is confirmed as north pole.

Question 5.
Why does a compass needle get deflected when brought near a bar magnet?
Answer:
The compass needle is a tiny, pivoted magnet which can turn freely in the horizontal plane. The compass needle has a north pole and a south pole just like any other magnet. A compass needle gets deflected when brought near a bar magnet because the bar magnet exerts a magnetic force on the compass needle.

Picture-Based Questions

Question 1.
a. Identify the device shown below.

b. In which direction does it point?
Answer:
a. Magnetic compass.
b. North-south direction.

Question 2.
Observe the given picture and answer the following questions.

a. What is happening in this image?
b. What type of material is used for this purpose.
Answer:
a. An iron strip is being magnetised by rubbing over a magnet.
b. Magnetic materials such as iron, nickel and cobalt are used for this purpose.