Assertion (A) : Steam is more harmful for human body than the boiling water in case of burn. Reason (R) : Boiling water contains more heat than steam.

Assertion (A) is true because steam causes more severe burns than boiling water at the same temperature. This is due to the latent heat of vaporization, which is the energy absorbed by water to transform into steam without a temperature increase [2]. When steam contacts the cooler human skin, it undergoes condensation, releasing this stored latent heat (approximately 2260 J/g) directly onto the tissue. Consequently, the skin receives significantly more thermal energy from steam than from boiling water, which only transfers sensible heat. Reason (R) is false because steam actually contains more total heat energy than boiling water; specifically, it contains the heat of the boiling water plus the additional latent heat required for the phase change [t1]. Therefore, boiling water contains less heat than an equal mass of steam at the same temperature.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > Explanation > p. 295
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > Latent Heat > p. 294