The vaporized heat causes hot steam to contain more heat energy and cause more severe burns than boiling water.
Water vapor contains both the heat of boiling water and the hidden heat of water vapor.
The steam that burns worse than boiling water is caused by the vaporized heat .
The vaporized heat is the thermal energy needed to convert a unit of liquid into a gas state at atmospheric pressure at its boiling point.
Boiling water only contains the amount of thermal energy needed to boil it. However, because the steam is formed from boiling water, it contains both the heat of boiling water and the hidden heat of water vapor. Therefore, steam has more heat energy, resulting in more burns than boiling water.