Air is a very useful natural resource, just like water, and has many uses. The most important aspect of air is that it keeps all living things on Earth alive by providing oxygen.
Living things are not the only things that use oxygen. Candles, fire, iron, picked fruit and vegetables all change when exposed to oxygen. Candles and fire require oxygen to continue burning. Iron will rust when exposed to water and oxygen. Fruit and vegetables will change colour and eventually go mouldy due to the moisture and oxygen in the air.