What is the reaction CuSO4 5H2o plus heat?

CuSO4.5H2O === heat===> CuSO4 + 5H2O

CuSO4.5H2O is the blue copper sulphate you have in a school chemistry lab.

When you heat it, it turns white to CuSO4, as the heat drives off the water of crystallization.

The analogy is like holding a ball(5H2O) in you hand(CuSO4). The ball is not part of you, but if your hand is 'twisted/(heated)' , then you let go of the ball.