Choose all the true statements concerning the law of conservation of mass:

a) When ice melts, mass is gained since water is more dense than ice.

b) 2H2 + O2 → 2H2O is a balanced equation

c) A chemical change does not follow the law of conservation of mass

d) A physical change does follow the law of conservation of mass

e) A pencil breaking is an example of a physical change

The answer would be:

b) 2H2 + O2 → 2H2O is a balanced equation

d) A physical change does follow the law of conservation of mass

The law of conservation of mass states that the mass can't be destroyed or created.

When water becomes ice, the volume is increased but the mass isn't. This will cause the ice to have a lower density than water.

That means the mass of the product will be same as the reactant so the number of atoms in the reactant should be same with the number of atoms in the product. Physical and chemical changes should follow the law of conservation of mass.