What is decomposition reaction? Give an example of decomposition reaction. Describe an activity to illustrate such a reaction by heating.

Decomposition reaction: The reaction in which a compound splits up into two or more simpler substances is called a decomposition reaction.

Example: When calcium carbonate is heated, it decomposes to give calcium oxide and carbon dioxide.

$CaCO_{3}\xrightarrow{Hear} CaO+CO_{2}$

Calcium carbonate −−−→ Calcium oxide + Carbon dioxide

Activity: When potassium chlorate is heated in the presence of manganese dioxide catalyst, it decomposes to give potassium chloride and oxygen:

$\ 2KClO_{3} \ ( s) \ \xrightarrow[MnO_{2}]{Heat} \ 2KCl\ ( s) \ +\ 3O_{2} \ ( g)
$

In this decomposition reaction, a single compound, potassium chlorate, is splitting up into two simpler substances, potassium chloride and oxygen.  It is used for preparing oxygen gas in the laboratory.