Question

D. Answer these questions.
1. How is air useful to us?
2. How is stratosphere a very important layer of atmosphere?
3. When a burning candle is covered with a glass, it gets extinguished. Why does this
happen? What does this activity show?
4. What is sedimentation and decantation?
5. Explain filtration with the help of a diagram.
6. What is distilled water? What are its uses?​

Answer 1

1. Air is very useful for us as from air we get oxygen which is most essential for the sustainability of life forms.
2. Stratosphere contains the ozone layer which protects is from the harmful ultraviolet rays of the sun.
3. This happens because oxygen is consumed during the process of burning. The covered glass prevent the surrounding air to mix with the air inside. Hence, when the amount of oxygen got exhausted the candle get extinguished. This shows that oxygen is essential for burning.
4. Sedimentation is a process of separation in which heavier particles settled down at the bottom of the container. Decantation is the process of separation of mixtures of immiscible liquids.
5. .....
6. Distilled water is the water that has been boiled into vapour and condensed back into liquid state. Basically it is the water free from any kind of impurities like minerals. Distilled water is used in laboratories and also in batteries.