A chemical reaction is a process in which a substance is changed into another substance by molecular interaction. An easy way to understand chemical reactions is to think of them as changes in energy. The website "Chemtutor" defines a chemical reaction as "a new material being made along with the disappearance of the mass that changed to make the new." Common chemical reactions can occur through oxidation, the application of heat, and decomposition.
Oxidation is the chemical reaction of oxygen on anything it comes into contact with. This includes the formation of rust on metal, a common chemical reaction. Another example of oxidation is the way a piece of fruit turns brown after you cut into it. The enzymes in fruit react to oxygen molecules, but this brown "rusting" of fruit is considered harmless.
Chemical reactions involving heat are easy to observe in activities such as cooking, baking, or even toasting a piece of bread. Heat changes the molecular structure of food, enhancing its flavour and changing its colour and its texture.
Another example of a common chemical reaction caused by heat is the striking of a match. Striking the tip of a match, which is dipped in a substance called red phosphorous, changes this ignitable substance into white phosphorous. White phosphorous reacts with air exposure and starts a flame.
Decomposition is a common chemical reaction in which an organism is broken down into smaller parts, or destroyed, by the breaking down of molecules. This process can be seen in the decomposition of all organic matter, including humans, other animals, and plants.
Easy Ways to Observe Common Chemical Reactions
Common chemical reactions can be observed in processes such as silver developing tarnish, iron or other metals rusting, an antacid neutralising stomach acid, and the natural sugar in grapes fermenting into wine. Many ordinary occurrences are actually chemical reactions. Leaves changing colour each autumn is a chemical reaction; the formation of compost is another example.