# The air, which has a relative humidity of 75% and a temperature of + 22 ° C, cooled down to + 14 ° C during the night.

The air, which has a relative humidity of 75% and a temperature of + 22 ° C, cooled down to + 14 ° C during the night. Does dew form in the morning?

In order for the water vapor in the air to turn into a liquid state (condense) or into a solid state, it is necessary that the air, having passed the saturation point, becomes supersaturated with water vapor. In this case, dew, fog, frost, frost or clouds can form in the surface air layer, but on condition that the air rises.
The dew point is the temperature at which moist saturated air becomes supersaturated.
1) According to the table, we determine that at a temperature of + 22 ° C Q = 19.6 g / m3, at a temperature of + 14 ° C Q = 12.2 g / m3.
2) Using the formula for relative air humidity: r = q: Q × 100%,
we derive the formula by which we determine the absolute humidity:
q = Q × r: 100% = 19.6 g / m3 × 75%: 100% = 14.7 g / m3
3) 14.7 g / m3 – 12.2 g / m3 = 2.5 g / m3 – each m3 of air can condense such moisture.
Answer: dew is formed in the morning because the air, which contains 14.7 g / m3 of moisture, will be oversaturated from the fact that the saturation state will be Q = 12.2 g / m3.

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