Steam at 100°C is more effective in heating than water at the same temperature because

Steam at 100°C is more effective for heating than water at the same temperature because it possesses a higher energy content due to the latent heat of vaporization. Latent heat is the energy absorbed or released during a phase change without a change in temperature. When steam comes into contact with a cooler surface, it undergoes condensation, transforming from a gas back into a liquid [2]. During this process, it releases the additional latent heat it absorbed during evaporation—approximately 2260 J/g—to the surroundings [1]. In contrast, liquid water at 100°C only transfers its sensible heat as its temperature drops. This extra energy release makes steam a more efficient heating medium and explains why steam causes more severe burns than boiling water, as it transfers significantly more thermal energy upon contact [t2][t3].

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 24: Hydrological Cycle (Water Cycle) > 24.3. Condensation > p. 329
2. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > Latent Heat > p. 294