One very important gas is oxygen. It is produced by plants during a process called photosynthesis. In this natural chemical reaction carbon dioxide molecules are combined with water molecules to produce a sugar molecule and oxygen gas.

This reaction is written as a chemical equation.

6CO2 + 6H2O --> C6H12O6 + 6O2

Oxygen can be produced in the laboratory using hydrogen peroxide and manganese dioxide. Click to see how oxygen supports combustion.


What the above chemical equation tells us is that 6 carbon dioxide molecules react with 6 water molecules to produce 6 oxygen molecules and 1 sugar molecule.
Oxygen can be produced in the laboratory by reacting manganese dioxide with hydrogen peroxide.

Oxygen is important to all life. Most life forms use oxygen to burn
the food in their bodies. Burning food releases energy which is then
used by the organism to sustain life.

The video on the right shows how oxygen supports combustion. A glowing wick is placed in oxygen and immediately ignites.



Look at the reaction of photosynthesis. Explain how we could not survive without massive forests on Earth.

Explain how we are creating a very dangerous situation when we cut down forests and increase the amount of cars on our roads. Hint - look at the products formed when petrol burns with oxygen..

We pour water onto fire to extinguish it. How does the water put out the fire?

Run the movie of oxygen supporting combustion.. Why is oxygen necessary for fuels to burn?
Hint- look at the energy released.


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