You are presented with the quiz "What can be done to a solid by adding heat energy?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "melting means changing from a solid into a liquid by adding heat energy" and "when a substance melts, it changes phase from a solid to a liquid by the application of heat". 

So, what's the best answer to the question?


 

      changing the phase     