I know how evaporation works in general, water molecules escaping and such… but I can’t for the life of me figure out how heat makes that process faster
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Imagine a glass of water like a billion microscopic balloons under a net that kinda keeps ’em in place, for the most part, but it’s got holes in it so it’s not gonna keep them there forever. At room temperature, they’re kinda just chillin’ in there, every once in a while a balloon towards the top gets bumped and escapes through a hole in the net. Of course it happens faster than “every once in a while” and it’s more than just one balloon, but that’s the general idea.
When you add heat, you are getting those balloons excited and they are moving around much more and bumping each other more, and so more and more start escaping through the net.
Heat is just energy.
Water molecules with more energy move around faster, which makes them collide with each other more violently.
On the top layer of the water, more molecules get bounced into the air due to these violent collisions. Think of it like popcorn popping, some of the kernels always go flying off across the room.
One of the very unique traits of water is just how much the molecules like sticking together. This is what gives water such amazing surface tension.
So, when there’s enough energy in the system to separate one molecule from the rest, the hard work is done. That molecule just goes off to do it’s own thing then.
When water gets hot, it starts to move and bounce around faster and faster. This makes the water molecules get more energy and they start to break apart from each other and turn into water vapor.
When the water molecules turn into water vapor, they rise up into the air and evaporate. So, more heat makes the water molecules move around really fast and turn into water vapor quickly, which makes the water evaporate faster.
Entropy! Water “wants” to be a gaseous. There’s two ways it does it; you bring it to 100°C, and it becomes steam, or it absorbs energy from around itself and becomes water vapour over time. More heat is more energy available is more vapourisation.
A Level chemistry blew my mind when we did this.
When water evaporates, it needs to absorb energy. This is called the latent heat of vaporization (this is exactly how sweating cools you down). If you add more heat to the water, there’s more energy available for the water to absorb in order to evaporate.
Heat=molecular energy in the form of atomic vibrations. The more energy the molecules have, the faster they bounce around, and therefore the more of them get flung out into oblivion.
Hence, hotter=faster evaporation.
This same principle is why ice is hard and steam is gas. Zero vibration turns to solid ice and maximum vibration puffs up into gas.
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