State the two laws of chemical combination.

The two laws of chemical combination are:

1. Law of conservation of mass:
The law of conservation of mass states thatduring a chemical reaction , mass is neither created nor destroyed. According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants.

2. Law of definite proportions:
The law of definite proportions, also called Proust's law or the law of definite composition, or law of constant composition states that a given chemical compound always contains same elements combined in fixed ratio (by mass) and regardless of the source and method of preparation of the compound.