Does water or steam burn your skin more and why?

Question

Just about everyone at one time or another has been burned by hot water or steam. This problem compares the heat input to your skin from steam as opposed to hot water at the same temperature.
Assume that water and steam, initially at 100 degrees C are cooled down to skin temperature (34 degrees C) when they come in contact with your skin. Assume that the steam condenses extremely fast. We will further assume a constant specific heat capacity c=4190 J/(kg * K) for both liquid water and steam.
Under these conditions, which of the following statements is true?

a) Steam burns the skin worse than hot water because the thermal conductivity of steam is much higher than that of liquid water.
b) Steam burns the skin worse than hot water because the latent heat of vaporization is released as well
c)Hot water burns the skin worse than steam because the thermal conductivity of hot water is much higher than that of steam
d) Hot water and steam both burn skin equally badly

I have an idea but it's mostly based on logic...can anyone help?? Thank you :)

Answer 1

The creation of steam involves a huge amount of energy know as the "Latent Heat of Vaporization" that is the heat absorbed when a substance changes phase from liquid to gas. To heat water takes about 1 BTU/lb per Deg F so heating water from 0F to 212F takes about 212 BTU's, but once it reaches 212 F it take about 1,000 BTU more to vaporize it, no change in temperature, still at 212 F. When steam burns your skin it must remove that same 1,000 BTU to condense the steam back to a liquid before the temperature falls.

Answer 2

It is the very high Latent Heat, about 540 cal/gram that is released when steam condenses. Compare that to 1 cal/g for every degree that water at 100 degrees loses when it touches your skin.

Answer 3

answer: Steam burns the skin worse than hot water because the latent heat of vaporization is released as well.