Chemical Change Examples

In chemistry there are usually two types of changes that can take place: physical and chemical. Physical are those that are usually less difficult and can usually be undone easily, even if over time. Chemical change, however, takes place when the internal make-up or the molecules of the object changes and is not reversible, unless of course there is another chemical reaction. It is a chemical process or reaction which causes such a change in the molecules of the object.

There are usually one or more new substances formed or created during a chemical reaction or change. A most likely clue to a chemical change occurs when the process produces a gas, light, smell, a fire or heat, or a color change (not with crayons).

Chemical changes may sometimes change the state of matter as well, but not always. For example, melting solid ice changing into water is not a chemical change because the molecules do not change. It is still water. A formation of a solid may take place when two gases are joined together. Chemical changes may also be accompanied by a gain or loss of energy.

Chemical changes take place every day in a person's life when new matter is formed. The new matter has a composition of molecules different from the original object or substance.

1. Burning wood in a fireplace: When the wood lights up and begins to gently burn it eventually turns into ashes. As it burns though, heat is produced, there is light, and the smoke is released through the chimney. The chemical reaction of the heat, light, and smoke are characteristics of a chemical reaction resulting in new matter, the ashes. The ashes cannot be turned back into the wood.

2. Ripening and rotten bananas: Several bananas are on the countertop at home. They are green when purchased, but eventually they begin to turn yellow and eventually ripen to the point of becoming rotten. The chemical composition of the bananas has changed over time resulting in new molecules. One cannot unripen a banana.

3. Rusting: A nail, or other metal begins rusting in the outdoors. It is due to the chemical reaction between the metal and the moisture in the air. The nail can be cleaned of its rust, but the rust itself cannot be turned back into the original metal.

4. Leaves in the autumn: During the spring and summer the leaves on trees are a vibrant green and give off oxygen as the plants make their own food through photosynthesis. However, when autumn arrives the chemical reaction causes the leaves to become brown and ultimately fall off the tree. The brown leaves cannot be turned green again.