Why is perspiration an effective means of cooling human skin? ...

[sammy]

Why is perspiration an effective means of cooling human skin?
  What will be an ideal response?

Question 2

Explain why the dew point temperature provides a better indication of the actual amount of water vapor in the air than relative humidity.
  What will be an ideal response?

[apple]

Answer to Question 1

ANSWER: An appropriate answer would be that evaporation is a cooling process, so when the air temperature is high and the relative humidity low, perspiration on the skin evaporates quickly, often making us feel that the air temperature is lower than it really is. However, when both the air temperature and relative humidity are high and the air is nearly saturated with water vapor, body moisture does not readily evaporate; instead, it collects on the skin as beads of perspiration. Less evaporation means less cooling, so we usually feel warmer than we did with a similar air temperature, but a lower relative humidity.

Answer to Question 2

ANSWER: Students need to demonstrate knowledge that the relative humidity does not represent the amount of water vapor in the air, but rather how close the air is to being saturated, which is why it is not a good indicator of humidity. In contrast, the dew point is a measure of the amount of water vapor in the air. High dew points indicate high water vapor content; low dew points, low water vapor content. The addition of water vapor to the air increases the dew point; removing water vapor lowers it.

[sammy]

Thanks for the timely response, appreciate it

[T4T]

TYSM