why does matter compress when it’s cold, but when you compress it, it generates heat like in the core of the sun.
In: Chemistry
Think of molecules as objects attached to one another with springs. They’re jiggling about a little bit, and the hotter they are, the more they jiggle. More jiggling = can stretch the springs more = spread out more = expands. The “springs” in these case are the weak forces between molecules, like the Van Der Waal force.
The core of the Sun is a totally different matter that involves a different kind of physics. The core of the Sun is hot because certain types of reactions that release huge amounts of energy only work in places where things are extremely close together. Those reactions aren’t on the level of molecules or whole atoms, but rather on the level of atomic nuclei (the Sun is too hot for full atoms to exist there, even at its surface).
The amount that matter compresses due to temperature is quite minimal. The sun is SO dense and compressed that the atoms undergo nuclear fusion. The concepts are not really comparable.
Molecules jiggle around. This jiggling is what we call heat.
When the object is cooled, the molecules jiggle less, so the molecules can be closer to each other with out colliding.
If we compress the matter, there’s the same number of jiggling molecules but in a smaller space. So the density of jiggles per unit of volume increases and this is heat.
[See 2mn10secs of this video](https://youtu.be/7J52mDjZzto)
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