Question

Why is a burn from steam typically much more severe than a burn from boiling water?

Short answer

A burn from steam is typically much more severe than a burn from boiling water because steam carries a larger amount of energy due to the latent heat of vaporization. When steam comes into contact with skin and condenses into water, it releases significantly more energy than boiling water alone. This higher energy transfer can cause more extensive damage to the skin and penetrate deeper into the tissue, resulting in a more severe burn.

Step-by-step solution

Understanding Latent Heat of Vaporization

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.

Comparing the Energy Transfer

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.

Severity of Steam Burns

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.