Propane burns in air to produce carbon dioxide and water. what is this type of chemical reaction called?

Combustion reaction

Explanation: Combustion is a type of chemical reaction in which a hydrocarbon burns in the presence of oxygen to form carbon dioxide and water and release large amounts of energy.

The balanced chemical equation representing the combustion of propane:

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.