Adrian Dingle, Educator and Chemistry Author with 25 years teaching experience
A decomposition reaction involves a chemical compound breaking down into simpler substances, or even its elements.
One great way to recognize a decomposition reaction is to look for a reaction where there is only a single reactant - that often signals a decomposition reaction.
Decomposition reactions are often caused by some external source of energy, which forces the substance to break down, for example,
In the electrolysis of water, electricity is used to break water into its elements.
2H2O(l) ==> 2H2(g) + O2(g)
In the decomposition of calcium carbonate, heat is used to split the compound into the two oxides.
CaCO3 ==> CaO(s) + CO2(g)