In a chemical change substances react to produce something new.
Chemical changes are also generally difficult to reverse.
Examples of chemical changes include
In asking yourself whether a chemical change has occurred answer these two questions.
Some of the signs that may occur during a chemical change include
When a red apple is sliced and left in the air it begins to go brown. There is a permanent change in color. The reaction is also difficult to reverse. So a chemical reaction has occurred.
If water is placed in a freezer it soon solidifies and becomes ice. The reaction is easily reversed by placing the ice in the sun. Since nothing new is formed and the reaction is easily reversed a chemical reaction has NOT occurred.