A burning candle is an example of a chemical change because the paraffin wax, which is a hydrocarbon, undergoes a chemical reaction with oxygen to form water and carbon dioxide gas. Because the chemical structure of the paraffin has been altered, this is a chemical change.
A change is described as either physical or chemical. Physical changes alter the form that a substance or mixture is originally in, but the substance or mixture could, in theory, be returned to the original state through physical means. Chemical changes, however, involve changing the structure of the material at the atomic level. In order to extract the original reactants, another chemical change would have to occur.