What happens to the amount of substance if it is changed from a solid to liquid

This change is called melting. When energy is added to the molecules in a solid the molecules start to move quicker and can break away from the other molecules. After the molecules have enough energy they begin to flow past the other molecules and that's what makes a solid turn into a liquid.

Answer: It will stay the same

Explanation: The volume doesn't change when transforming states because matter can't be created nor destroyed only transformed.