Chemical reactions

Chemical reactions change the properties of the original substance, and a new substance is formed.

Here are three types:

Combustion produces energy in the form of heat and light. Combustion (or burning) can happen when oxygen in the atmosphere reacts with a fuel, such as wood, gas, or oil.

Oxidation can occur with metals (rust) or in foods like apples.

Fermentation is a chemical reaction where fungi or bacteria change organic substances into other substances.

During the process of fermentation, fungi produce alcohol and bacteria produce lactic acid.  This way we can get foods like yoghurt, wine, bread, and cheese.