When you touch something very hot you move you your hand away from the object as soon as you feel the sensation why is this so?

This is an automatic response known as a withdrawal reflex. It is your body's way of protecting itself from harm by quickly moving away from a potential threat (in this case, the hot object) to prevent injury. The sensation of heat is detected by specialized nerve endings in your skin, which send a signal to your spinal cord to trigger the reflex action.