Steam

[Rhea Palsule]

When steam touches the skin, Dr. Lavelle explained how first it would phase change to water (40.7 kJ/mol) and then would decrease in temperature, still in the liquid phase. Could you predict how much the temperature of the water will actually decrease by taking the average of the temperature of the steam and the skin? Or do volume of the steam and/or surface area of the skin also play a role in the amount of temperature decrease?

[Chem_Mod]

Hi Rhea,
Yes and No actually. Yes because you can predict the decrease in the temperature of water and No because you cannot take the average to find it. And as far as the volume of the steam and surface area of skin exposed go, yes they will definitely influence the final temperature of the water.

The basic idea behind finding the final temperature of water is to know that – The heat released by the steam and water (after the steam condenses) is equal to the heat gained by the skin. The heat released by the steam/water will lead to a fall in temperature of steam/water and the heat gained by the skin will lead to an increase of the skin temperature.

You cannot take an average because skin and water have different heat capacities. So to find the final temperature you will need to know some extra information.

[Daniella Ching 4C]

Will we need to solve problems where we have to find the change in heat and then use that and the specific heat capacities to calculate the final temperature of the water or of skin?