Latent heat

ice melting On a hot day, you will perspire or sweat to cool down but how does perspiration cool the body down. The water on the surface of our skin evaporates (turns into a vapour) this takes energy and this energy is taken from the body which cools. It is important to replace the fluids lost throught perspiration so that the body does not become dehydrated.

Dogs don’t have many sweat glands, so they cool by panting, which evaporates water through the mouth and tongue.

When an object is changed from a solid to a liquid (melted) or from a liquid to a gas (boiled), heat must be added or removed. This heat is called Latent Heat. This energy is used to break down the bonds that hold the atoms together. When an object melts we call it is called the Latent Heat of Fusion and when it boils we call that the Latent Heat of Vaporization

Amount of heat needed to melt a substance = Latent Heat of Fusion x mass

Amount of heat needed to boil a substance = Latent Heat of Vaporization x mass

Image from Wikipedia

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