Large stores of energy are required for liquid to transform into gas, and this energy is released all at once when steam hits the skin and transforms back into a liquid. This results in a burn more severe than one caused by water of equivalent temperature, says UCSB ScienceLine.
A steam burn can cause more damage than boiling water of the same temperature. When boiling water makes contact with the skin, it decreases in temperature but does not undergo a phase change like steam, states the University of British Columbia. Steam decreases in temperature as it hits the skin, condensing into liquid and undergoing a phase change. This change releases energy quickly enough to damage skin cells more severely than boiling water, even when the water is the same temperature as the steam.