Achange occurs when a substance changes phase. physical chemical nuclear user: the latent heat of vaporization of ethanol is 200 calories/gram. this means that about 200 calories of heat must be added to 1 gram of ethanol to change its temperature about 200 calories of heat must be added to 1 gram of ethanol to convert it from a solid to a liquid about 200 calories of heat must be added to 1 gram of ethanol to convert it from a liquid to a gas