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New thermoelectric generator converts vehicle exhaust heat into electricity, boosting fuel efficiency
(www.inceptivemind.com)
this post was submitted on 14 Feb 2025
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I’ve wondered about this. If this is so, and heat is molecules moving back and forth, how do the molecules stop, change direction, and then accelerate in the other direction, stop, change directions again, and go back, over and over and over?
It's pretty much like billiards. They just bounce. Different chemicals (types of molecule) are different phases at different temperatures e.g. nitrogen is a gas at room temp, water is liquid. Stuff that's a gas at room temp just has less bonding forces (and often mass) than liquids or solids. So they don't take as much heat to go fast. There's a lot of heat even at room temp, and even at -40deg. The temperature for nitrogen to sit in one place is -210C or -346F.
Yeah, I do apologize - I'm somewhat simplifying my explanation because when you start going into the full detail, it just brings up more questions.
So yes, like the other comment says, the particles are constantly bouncing into other things.
Nothing to apologize for - thank you for elaborating.
Molecules interact with each other. Energy is transferred as they bump around. If you were to follow a single molecule it would move around randomly. What we can measure is usually the average of many molecules.
So it’s less of vibrating and more about smashing around into things?
This is easier to envision with a gas: like a chamber of balks all ricocheting like mad. It’s harder to envision for a solid. But I guess a molecule will be up smack against its neighbors, getting repelled, not so much bounding freely?
So in a solid, you can imagine each atom connected to each other by springs (bonds). They can vibrate on these springs. If they vibrate too much (by heating) then they can break the bonds and escape as a gas. Gasses basically have too much energy to bond again.
Even solids are mostly nothing. This is why neutron stars are so dense - there is a lot less nothing between the neutrons, largely due to gravity.
Here's another way to think about it. A gas is like a bunch of balls bouncing around a room, hitting the walls and occasionally each other. A solid is like a ball pit, but the balls are vibrating. There is still a lot of bouncing, but most of themstay together.