Mass is conserved in a chemical reaction Atoms of Atoms of nd of element x element y X and y 16X 8Y 8 XY Law of mass conservation(质量守恒定律): There is no detectable change in the total mass of materials when they react chemically to form new materialsMass is conserved in a chemical reaction Law of mass conservation (质量守恒定律): There is no detectable change in the total mass of materials when they react chemically to form new materials 16 X + 8 Y 8 X2Y