Page 5 - Curriculum Visions Dynamic Book

All kinds of fuels can “burn” in the sense of being oxidised by oxygen, although not all give out large amounts of heat. The carbohydrates in our food, for example, oxidise to release energy for our bodies. When dead organic material decays, it is actually oxidising. Oxidation also happens to food left exposed to the air and to the cells in our bodies.
Oxygen reacts with most metals. Sometimes
the effects cannot be seen, such as when an invisible oxide film forms on the surface of a
sheet of aluminium. But other metals react more dramatically. Iron, for example, reacts with oxygen in the presence of water to produce the familiar flakes of rust, while potassium instantly catches fire.
The formula for oxygen gas is written as O2. This means that oxygen gas (like most other gases) normally occurs as a molecule, made of two atoms, rather than as a single atom. Most single atoms of oxygen occur high in the atmosphere. Oxygen can also occur as a molecule with three atoms, in which case the chemical symbol is O3. This form of oxygen is called ozone and it has quite different properties from the more plentiful O2, including the property of shielding living things from the harmful ultraviolet radiation of the Sun. Scientists are worried that the amount of ozone in the atmosphere is now so low that it is no longer an effective shield.
 This flame is created by the reaction of propane gas and oxygen. The heat given off by the reaction is quite sufficient to warm the air and lift the balloon. (The other products of the combustion reaction are carbon dioxide gas and water vapour.)
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