Submitted by MindTheReddit t3_zo23xk in askscience
thewrongequation t1_j0kt6ki wrote
High humidity means that a higher proportion of air is made up of water molecules than air of low humidity. Water has a higher heat capacity than, and is a better thermal conductor than, the other things that make up air (mostly nitrogen and oxygen). So it gives and takes away thermal energy much more efficiently. Just like how, if you touch a piece of metal and a piece of plastic that are at room temperature, the metal will feel colder than the plastic, even though they are the same temperature, because the metal is a better thermal conductor and so is better able to take the thermal energy away from your hand.
kilotesla t1_j0l97vf wrote
However, at 40 F = 4.4 C, 100% relative humidity means only 0.5% of the air is water vapor, so its impact on the heat capacity of the air is negligible.
tatodlp97 t1_j0mzgnv wrote
What we see as humidity in weather forecasts is more specifically relative humidity (RH).
It ranges from 0% to 100%. 0% humidity means there’s practically no water vapor in the air. 100% humidity implies that the air is saturated with water, meaning it has the highest concentration of water vapor that can be held at that specific temperature. Any addition of water vapor will lead to it condensing into a liquid creating a cloud or fog. This can also occur when the water concentration is held constant but the air temperature drops. Colder air can hold less water valor which results in the excess concentration of water condensing again into fog. That’s how most clouds form where humid warm air from the surface rises and it expands due to lower pressure, causing it to cool (through adiabatic cooling) and the now excess moisture crashing out of the gaseous phase.
StandardSudden1283 t1_j0l11fe wrote
Question about those aerogels that can be placed in a furnace, get red hot, then be handled with bare hands.
I understand they have low thermal conductivity but is there a/what is the relation to their thermal capacity?
fuzzygondola t1_j0l54f0 wrote
Thermal conductivity and specific heat capacity don't go hand in hand. But heat capacitance depends on the material and its mass. Aerogel is extremely light and that why it doesn't burn you even when it's red hot.
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