Chemical Reactions and Equations — Science STD 10 — Question

Those reactions in which a compound splits up into two or more simpler substances are known as decomposition reactions.
Example: When calcium carbonate is heated, it decomposes to give calcium oxide and carbon dioxide.
They are called opposite of combination reactions because in a combination reaction, two or more substances combine to form a single substance.
Example: Magnesium and oxygen combine, when heated, to form magnesium oxide.