Chemical change
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A chemical change (chemical reaction) is a change in which one or more new substances are formed. Burning of wood is a chemical change as new substances which you cannot change back (e.g. carbon dioxide, water vapour) are formed. Other examples: burning of a candle, rusting of iron. Special details that describe how a chemical change takes place are called chemical properties.
Compare: Physical change - A physical change is a change in which no new substances are formed. Examples: changes of shape, changes of states, passing electricity through a copper wire. Special details which do not change in a substance without new substances being formed are called physical properties.
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