Give two uses of the following component present in the air : 

carbon dioxide. 

Give two uses of the following component present in the air :

water vapour.

Define the following : 

Respiration.

Define the following : 

photosynthesis.

Define the following : 

combustion. 

What are fuels? Give two examples of modern fuels.

Give reasons: 

Aquatic animals and plants are able to survive in water. 

Give reasons : 

A burning candle stops burning if covered with a glass tumbler. 

Give reasons : 

Mountaineers and divers carry oxygen cylinders with them.