Question

which of the following would cause a chemical change in water?
A) boiling water to converted from a liquid to a gas
B) adding sand to make amixture of sand and water
C) adding electric current to seperate hydrogen from oxygen
D) freezing the water to convert it from a liquid to a solid

Answer 1

Boiling and freezing don't change the identity of our compound b/c no chemical bonds are broken. Any phase change is a physical property. I mean in boiling you are putting in energy to break bonds but that's between the water molecules.

Separation by sand, wouldn't be it.

If you pass an electric current, that causes your identity of the substance to change so it's no longer water

2H2O ---> 2H2 + O2

Answer 2

C would make the most sense to me. So phase changes are also thought of as equilibrium.