You are presented with the quiz "What does boiling change a liquid into?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "heating a liquid can be used to identify that liquid 's boiling point" and "because at the boiling point of water, there are molecules that are a gas and that are a liquid". 

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


 

        gas   