• In a combination reaction, two or more substances combine to form a single new substance.

• In a decomposition reaction, a single compound breaks down into two or more simpler substances.

• It involves two or more reactants combining.

• It involves one reactant that breaks down.

• It produces one new compound.

• It produces two or more products.

• These reactions commonly occur in synthesis processes, such as photosynthesis and combustion.

• These reactions often occur in processes like thermal decomposition, where heat is applied.

• An example of a combination reaction is when hydrogen gas combines with oxygen gas to form water: 

      \(\rm 2H_{2}\)+ \(\rm O_{2}\) → \(\rm 2H_{2}O\)

• An example of a decomposition reaction is when water is broken down into hydrogen and oxygen gases:

         \(\rm 2H_{2}O\) → \(\rm 2H_{2}\)+ \(\rm O_{2}\)