CBSE Important Questions Class 6 Science Chapter 11 – Nature’s Treasures

Class 6 Science Chapter 11 Nature's Treasures is part of the new NCERT textbook Curiosity. It teaches students about the natural resources around us, such as air, water, soil, forests and minerals. Students learn which resources are renewable and which are exhaustible, what air is made of, how plants keep the gases in the air balanced, how wind and sunlight are used to make electricity, and why pollution and deforestation are harmful.

These CBSE important questions for Class 6 Science Chapter 11 cover the causes of air pollution and ways to reduce it, how wind speed and location affect a wind farm, reading a pie chart of the gases in air, the properties of air, the link between photosynthesis and breathing, the long-term effects of cutting down forests, and the advantages of renewable energy over fossil fuels. Every question has a clear step-by-step answer in simple English with figures, so students can practise on their own, parents can check the working, and teachers can use them for class tests. A free printable PDF of these important questions is also available on this page.

Q1. Air is a renewable resource, but it can be polluted. Discuss some of the ways air pollution can occur and suggest methods to reduce it.

Answer: How air gets polluted:
i. Vehicles: Cars, buses and trucks give out harmful gases and smoke.
ii. Factories: Industries and power plants release chemicals, smoke and carbon dioxide.
iii. Burning fossil fuels: Burning coal, oil and gas for energy adds harmful gases to the air.
iv. Farming: Too much use of pesticides and chemical fertilisers pollutes the air.
How to reduce it:
i. Use renewable energy such as solar and wind power instead of fossil fuels.
ii. Use buses, trains and other public transport so that fewer vehicles run on the road.
iii. Plant more trees, which take in carbon dioxide and give out oxygen.
iv. Use eco-friendly products and make factories control their smoke.

Q2. An engineer plans to set up a wind farm to generate electricity. In order to choose the best location for the wind turbines, he needs to consider several important factors.
a. How do factors like wind speed and direction affect the efficiency of the wind turbines of a windmill?
b. What would be the difference in windmill efficiency in a mountainous and a coastal region?
c. How might the frequency of storms or seasonal wind patterns influence the long-term performance of the wind farm?

Answer: a. Faster wind turns the blades harder and makes more electricity, while slow wind produces very little power. The turbine must also face the direction from which the wind is blowing, otherwise it cannot catch the wind properly.
b. In a mountainous area the hills block the wind, so the turbines get less wind and work less well. In a coastal area the wind from the sea is usually strong and steady, so the windmills work much better.
c. Storms can damage the blades and the tower, so the farm may have to stop working for repairs. But where the winds follow a regular pattern through the seasons, the farm can give steady power all year.

Q3. Observe the pie chart given below and estimate the amount of oxygen present in a sample of air weighing 150 tons.

Answer: From the pie chart, oxygen makes up 21% of the air.
Weight of oxygen = 21% of 150 tons
= (21/100) × 150
= 31.5 tons
So, 31.5 tons of oxygen is present in the sample.

Q4. State whether the given statements are true or false. Rewrite the false statements correctly.
a. Air is mainly composed of oxygen and carbon dioxide.
b. Air is important for respiration in animals only.

Answer: a. False. Air is mainly made of nitrogen (about 78%) and oxygen (about 21%). Carbon dioxide and other gases are present only in very small amounts.
b. False. Air is important for respiration in both animals and plants. Plants also need the carbon dioxide in air for photosynthesis.

Q5. Describe how plants help in maintaining the balance between different components of air.

Answer: Green plants make their food by photosynthesis. In this process they take in carbon dioxide from the air and give out oxygen.
All living things, including plants, use up oxygen and give out carbon dioxide when they breathe. Because plants do the opposite during the day, the amount of oxygen and carbon dioxide in the air stays balanced. This is why planting trees is so important for life on Earth.

Q6. Observe the machinery in the image given below, followed by its properties.
I. It can only work during daytime.
II. It can be used to generate electricity.
III. It produces clean and renewable power.
IV. In India, it can be operated with maximum efficiency in Jammu and Kashmir.
Which of the following options is correct with respect to the properties of this machine?
(a) I and IV
(b) I and III
(c) III and IV
(d) I, II and III

Answer: (d) I, II and III
The machine is a windmill. It is used to generate electricity (II), and the power it makes is clean and renewable because wind never runs out and gives no smoke (III). Statement IV is wrong: windmills work best in windy coastal states such as Tamil Nadu and Gujarat, not in Jammu and Kashmir.

Q7. During the process of photosynthesis, gas P is used by plants while Q is liberated; however, during breathing, R is inhaled and S is exhaled. Based on the gases involved in each of the given processes, identify the correct option.
(a) P and S are the same
(b) P and R are the same
(c) Q and S are the same
(d) Q and R are different

Answer: (a) P and S are the same
In photosynthesis, plants take in carbon dioxide (P) and give out oxygen (Q). In breathing, we take in oxygen (R) and give out carbon dioxide (S).
So P = carbon dioxide and S = carbon dioxide, which means P and S are the same gas. Also Q and R are both oxygen, so they are the same, which makes options (c) and (d) wrong.

Q8. Consider the following processes.
I. Irrigation
II. Winnowing
III. Combustion
IV. Photosynthesis
Which of these processes require the involvement of air?
(a) Only I
(b) I and IV
(c) I, II and III
(d) II, III and IV

Answer: (d) II, III and IV
Winnowing needs moving air (wind) to blow away the light chaff. Combustion (burning) needs the oxygen in air. Photosynthesis needs the carbon dioxide in air. Irrigation only means watering the fields, so it does not need air.

Q9. Given below are different properties of natural resources. Identify the ones that describe air.
A. Opaque
B. Transparent
C. Invisible
D. Occupies space
E. Colourless
(a) A, B and C
(b) A, C, D and E
(c) B, C and E
(d) B, C, D and E

Answer: (d) B, C, D and E
Air is transparent (we can see through it), invisible (we cannot see it), colourless, and it occupies space, which we can show by pushing an empty inverted glass into water. Air is not opaque, so A is wrong.

Q10. The most crucial natural resource without which one can become unconscious in a very short duration is _______.
(a) water
(b) sun
(c) air
(d) minerals

Answer: (c) air
We can live for some days without food and for a short time without water, but we cannot live for more than a few minutes without air. The oxygen in air is needed every moment for respiration, so without it a person becomes unconscious very quickly.

Q11. The city's urban development authority developed a township that covered a vast forest area. Many trees were cut down to build homes and roads, and timber was used for various purposes. This led to the destruction of habitats of many animals and a decrease in the amount of oxygen in the atmosphere.
a. What could be the long-term effects of cutting down too many trees in forests?
b. How does deforestation affect the balance of natural resources?
c. What are some possible solutions to prevent deforestation?
d. What role do forests play in maintaining soil quality?
e. Does deforestation contribute to climate change and affect agricultural practices?

Answer: a. Cutting too many trees leads to soil erosion, so the land becomes less fertile and harder to farm. Animals lose their homes, and many kinds of plants and animals may disappear.
b. Trees take in carbon dioxide and give out oxygen. When large numbers of trees are cut, carbon dioxide builds up and oxygen falls, so the gases in the air lose their balance.
c. Create protected forest areas, hold tree-planting drives, use recycled paper and wood products, and make strict rules against illegal cutting.
d. The roots of trees hold the soil particles together so that rain and wind cannot wash or blow the soil away. Fallen leaves rot and add nutrients back to the soil, and they also help the soil hold moisture.
e. Yes. More carbon dioxide in the air makes the Earth warmer and changes the pattern of rainfall. The soil also loses its nutrients, so crops grow poorly and farming in the region suffers.

Q12. The country has been facing pollution and environmental damage due to the burning of fossil fuels like coal and natural gas. As a result, the government decided to invest in renewable energy sources like wind, solar and geothermal power. People are encouraged to use solar panels in their homes, and the government has built wind farms in areas with strong winds.
a. What are the advantages of using renewable energy sources over fossil fuels?
b. What actions can people take to support this change?

Answer: a. Renewable sources such as the sun and the wind will never finish, while coal, oil and gas will run out one day. Renewable energy also gives out almost no smoke or harmful gases, so the air stays clean and there is less damage to the environment. Once the panels or turbines are set up, the energy itself is free.
b. People can put solar panels on their roofs, use solar water heaters, switch off lights and fans when not needed, use energy-saving LED bulbs, travel by public transport or bicycle, and plant trees. Together these steps cut down the use of fossil fuels.

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