What is air?

You cannot see or smell  air. However, it is just as important for life as water and food. What is air, actually? Formerly, air was supposed to be a pure substance; today we know that it consists largely of nitrogen and oxygen, and that the vital oxygen is the lesser of the two main components.
In the following experiment you get to know the two main components of the air better and find out how they differ.


1. Your teacher fills your ampoule with oxygen from a gas cylinder and your infusion bottle with nitrogen from a second gas cylinder. (more see below)

2. Stopper the two vessels immediately and label them accordingly.

3. Ignite the wooden splint with the help of a tea light.

4. Open the bottle of nitrogen gas with the opening downwards. Hold the flame inside from below.

5.     Ignite the wooden splint again; blow out the flame so that the tip of the splint only glows.

6.     Dip the glowing splint into the ampoule with the oxygen gas.

7.     Dip a burning splint into an infusion bottle filled with air for comparison.


1.     Write down your observations.

2.     Explain the basis on which the properties the two gases are distinguishable.

3.     Find out about the composition of air.

4.     Explain why it is dangerous to allow naked flames in a room with high concentration of oxygen or with pure oxygen.

5.     Visualize the composition of air with the help of beads as models of particles.

6.     Carbon dioxide is present in the air in a very small proportion (about 0.04 %).

7.  How many beads of nitrogen and of oxygen would you need to show the correct ratio for a single particle of carbon dioxide?

First published: 05.09.2013                                                              Last modification: 18.07.2014