Explain how an equation can be balanced even if the number of reactant particles differs from the number of product particles.
By the Law of Conservation of Mass, Mass can neither be created nor destroyed. It can only be transformed. In transforming the gases of hydrogen and oxygen into hydrogen peroxide for example, the number of hydrogen molecules and the number of oxygen molecules as reactant particles will yield a different number of hydrogen peroxide molecules as product particles:
1H2 + 1O2 --> 1H2O2
So here we have 2 reactant particles making 1 product particle, but note that the number of hydrogen and oxygen atoms is the same.