Question

explain in terms of molecules, why thermal energy must be supplied for a solid to become a liquid.

Answer 1

For solids to turn into liquid we have to free them from the inter molecular forces between them .

For doing that we have to provide it with thermal energy.

The molecules begin to vibrate and when more heat is given the vibration will be at such an extent that they break free from th forces that was binding them and the solid becomes a liquid