HumidityIt's a hot summer day 100 degrees F and 50% humidity. How many grams of water vapor are there per cubic meter of air?

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litteacher8's profile pic

litteacher8 | High School Teacher | (Level 3) Distinguished Educator

Posted on

I have little to add to the answer above, except to state that air often feels much more hot the more humid it is. So if it is 100 degrees, it will be hot but bearable. But if it is 100 degrees and this humid, it is going to feel very hot and uncomfortable, and not bearable.
mrsdelossantos's profile pic

mrsdelossantos | High School Teacher | (Level 2) Adjunct Educator

Posted on

The basic principle here is that warmer air can hold more water vapor. Think of air like a sponge... warmer air can "hold" more water vapor because there are more spaces in between the air molecules due to the higher energy of the molecules. Remember that temperature is a measure of the amount of energy in a system. So, higher temperatures equal higher speeds. Thus, warm air molecules are farther apart than cold air molecules. Conversely, cold air cannot hold as much water vapor--that's why dew forms in the early morning, when air temperatures are at their lowest (at this time, the air cannot hold any more water vapor, so in a sense it gets "squeezed" out, just like a sponge that cannot hold any more water).

So, at 100 degrees F, air can hold 45.7 grams of water vapor. If the relative humidity is 50%, then 50% times 45.7 equals 22.8 grams of water vapor per cubic meter of air.

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