CBSE Class 6 Science Our Earth Assignment Set D

Question1) Name the two main gases found in air?
Answer.1) Oxygen & nitrogen.

Question2) Gently exhale some air over a clean glass plate with your mouth. Explain why the glass plate appears misty for some time.
Answer.2) When air comes in contact with cool surface of the glass it gets cooled. Some of the vapour present in air gets converted into water droplets. This forms mist on the surface of the glass plate.

Question3) How do clouds form?
Answer.3) When vapour reaches a certain height, it gets cooled and turn into very tiny water droplets. These droplets become visible to us in the form of clouds.

Question4) Why is atmosphere necessary? What is the importance of atmosphere?
Answer.4) Atmosphere is necessary due to following reasons:
1. The atmosphere acts as a blanket to protect the life on the earth.
2. It controls the temperature of the earth’s surface.
3. This helps the existence of life on the earth.

Question5) How does atmosphere control the temperature of the surface of the earth?
Answer.5) The light & heat from the sun first fall on the uppermost layers of the atmosphere.
The atmosphere allows only a part of this heat to reach the surface of the earth.
Remaining is absorbed by the atmosphere.

Question6) How is presence of nitrogen in atmosphere a boon?
Answer.6) Because, it slows down the rate of burning of materials. The nitrogen in the air keeps the process of burning under control. Unlike oxygen, nitrogen neither supports burning nor it burns itself.

Question7) Give uses of nitrogen other than present in atmosphere?
Answer.7) Nitrogen is used on large scale for manufacturing of ammonia, urea and fertilizers.

Question8) Mention any two properties of water that make it a special liquid?
Answer.8) It can dissolve a very large number of minerals in it and is a universal solvent.
It heats up or cools slowly as compared to solids and other liquids. It can store good amount of heat.

Question9) Name any two important materials that are obtained from oceans?
Answer.9) Salt and Iodine.

Question10) Explain why is soil an essential requirement for the existence of life on earth?
Answer.10) Most of the plants cannot live without soil, and animals cannot survive if there are no plants. Therefore, soil is essential for the existence of life on earth.