Question

Which property of physical changes explains why matter is conserved in a physical change?

Answer 1

Do you mean `"physical change"` or `"chemical change"`?

Explanation:

Mass is always conserved in a chemical change, which process involves involves the rearrangement of atoms and molecules. Of course most physical changes also conserve mass: when `10*g` of liquid water is frozen, you are left with `10*g` of solid ice.

Of course, there are also nuclear reactions (I am bit reticent, because I don't know whether I should put this under the `"physical"` umbrella). In nuclear fusion and fission, matter is not conserved, and can be converted into energy, with the result that the energy output/input dwarfs those observed in chemical reactions.