how do puddles evaporate/dry up on cold days?



how do puddles evaporate/dry up on cold days?

In: Chemistry

A puddle of water has an average temperature. But that is just average. Some molecules are much hotter and some are much colder – heat and cold being a measure of how fast the molecules are moving.

In any blob of water, some molecules of water are evaporating into the air at any time. And some water in the air is condensing into the blob of water.

If the air is at 100% humidity, the water evaporating and condensing is balanced.

If the air is not at 100% humidity, more water is evaporating than condensing. So the water will eventually all evaporate. It just takes longer if the water is cold on average than if it is hot on average.

The molecules in liquid water are held together slightly so that they are pretty much free move around as long as they stay next to each other. When the molecules have enough kinetic energy to escape the force holding them together, the molecules are considered water vapor.

Temperature describes the average amount of heat energy. At any given temperature, some water molecules can have more energy and some less. Even in very cold water, some of the most energetic molecules can have enough energy to escape. The hotter the water is, the more likely it is for molecules to escape.

Somebody asked today why water evaporates when it’s not above boiling point, and the answer to that question and this one are the same. Not all particles have the same amount of energy, some have more than the average. Some of these even have enough energy to escape the liquid and evaporate. Over time the entire puddle can evaporate this way. This is also what happens on hot and sunny days, only then it happens quicker.