A chemical change (chemical reaction) is a change of materials into other, new materials with different properties, and one or new substances are formed. Burning of wood is a chemical change as new substances which cannot be changed back (e.g. carbon dioxide) are formed. For example, if wood is burned in a fireplace, there is not wood anymore but ash. Other examples include burning of a candle, rusting of iron, baking a cake, etc. Special details that describe how a chemical change takes place are called chemical properties.