Topic 3 - Oxygen in air

• The main constituents of air are oxygen and nitrogen. There are also small quantities of water, carbon dioxide, sulphur dioxide, lead compounds and oxides of nitrogen produced by the burning of fuels. 
• The composition of air is not fixed. 

OXYGEN

• Oxygen is the gas that all living creatures need for respiration. It is also necessary for combustion, or burning. 

• 21% of the air is oxygen. 

• You can measure the amount of oxygen in air by removing it chemically. In the laboratory this can be done by making the oxygen react with hot copper. The product is copper oxide, which is a solid, and all that is left is nitrogen and the other trace gases in the atmosphere. Inside one syringe there is 100cm cubed of air. The second syringe starts off empty, and both are very well greased to ensure that gas…