Air - part 2 - 5th class

Composition of Air

Air is a mixture of many gases. It has 78% nitrogen, 21% oxygen, 0.9% argon & 0.03% carbon di oxide, with very small percentages of   water vapour & other gases. It also contains suspended dust, spores & bacteria. 

Nitrogen: Living things need to make proteins. Nitrogen cannot be used 

                 directly from the air.Bacteria present in the soil convert nitrogen

                  into soluble forms which are taken  in by the roots of the 

                  plants along with water. Plants make proteins with this

                 nitrogen. 

Oxygen: It is the most important part of air. It is used by all living things

                for respiration.

Carbon di oxide: Plants use it to make their food & give out oxygen that 

                             we take in. It also absorbs heat & thus keeps the 

                            earth warm and makes life possible on the earth.

Water vapour: It is present in the air as a result of the evaporation of  

                          water from seas, rivers &  oceans.