1. Air occupies _________________________.
2. Harmful gases and smoke in the air causes _________________________.
3. The _______________________ and ______________________ within the nasal passage prevents entry of dust particles into our respiratory system.
4. Air helps in _________________________ of sound.
6. Air is really not one substance but a __________________.
7. The component of air that supports burning is called ________________.
8. The aquatic animals use dissolved Oxygen in water for respiration, this is possible because Oxygen ________________ in water.
9. Nitrogen of the air is used on a large scale to manufacture ________________.
10. ________________ is the place in nature for gaseous exchange.
 Choose the correct answer :-
1. The height of the atmosphere is (120 km/240km)
2. The volume of oxygen (increases/decreases) with increase in altitudes.
3. (Carbondioxide/Oxygen) is taken in by the plants for photosynthesis.
4. Air contain approximately (78 percent/80 percent) of Nitrogen.
 II. True or False statements :
1. Air is a compound but not an element.
2. Air is an opaque material.
3. Air contains water vapour.
4. The major part of air is Nitrogen.
5. Plants produce Oxygen through photosynthesis.
 Name the following :-
1. The two scientists who proved air is a mixture of gases :
2. The lightest gas in the air.
3. The gas essential for combustion and respiration.
4. The substance in presence of which photosynthesis takes place :
 Define the following :-