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Latent heat of vaporization is the amount of energy required to change a substance from the liquid phase to the gas phase without changing its temperature. For water, this energy is significant - approximately 2260 kJ/kg. This means that when water turns into steam, it absorbs a large amount of energy from its surroundings. Conversely, when steam comes into contact with skin and condenses back into water, it releases this energy, causing a severe burn.

When a person is burned by boiling water, only the energy of the water itself is transferred to the skin. The specific heat capacity of water is approximately 4.18 kJ/kg.K, which means that when boiling water at 100°C comes into contact with the skin, this amount of energy is transferred per unit mass for each degree temperature difference between the water and the skin. However, when a person is burned by steam at the same temperature, a much larger amount of energy is transferred. First, the steam releases its latent heat of vaporization as it condenses on the skin, transferring approximately 2260 kJ/kg of energy. In addition, once the steam has condensed into water on the skin, it still has to cool down and will additionally transfer energy related to its temperature.

Since steam carries a larger amount of energy compared to boiling water due to the latent heat of vaporization, the amount of energy transferred to the skin upon contact is much greater in the case of a steam burn. This higher energy transfer can cause damage to a larger area of skin and can penetrate deeper into the tissue, resulting in a more severe burn. That's why steam burns are typically more severe than burns from boiling water.