3. How will you prove that air supports burning?
4. How will you show that air is dissolved in water?
5. Why does a lump of cotton wool shrink in water?

Dear student.

3.  Burn the camphor in a open glass bottle, it will keep burning till the bottle is open. As soon as the bottle is closed, the fire extinguished due to air cut-off. This confirms that air support burning.

4.  To show that air is dissolved in water we take water in a pan and heat it. Just before it boils, you will notice some bubbles at the inner surface of the pan. These bubbles are formed because of air dissolved in water.

5.  A lump of cotton wool shrinks when immersed in water. This is because air present in the cotton wool escapes . Thus, the volume of the cotton wool decreases.


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