I feel like I’m missing a part of basic chemistry understanding. What happens to rock on a molecular level when it melts? Does its composition change? Do all things melt under the right conditions?
In: Chemistry
So thermal energy (heat) is just a measure of atoms shaking about. If things only jiggle a little bit, then small electric forces (and some other stuff) can hold them in place on relation to one another which makes things solid. If they jiggle a bit more, you get a liquid. If they jiggle so much that other forces can’t restrain them much at all, you get a gas. If they jiggle so much they start falling apart, you get plasma (though things get a bit odd here). Making something really stable and big shake about requires a lot of energy, which is why some things can stay solid at higher temperatures while small and unstable things are already gases.
Things cooling down just goes in the opposite direction.
In this sense, yes. All things can melt. “Rock”, as everyday people think about it, have no singular composition. Some are uniformly one mineral, while others are made up of many. When these multi-mineral rocks melt, even if the minerals themselves don’t chemically change, the layers can separate much like how a milkshake left out on the counter will separate into different layers. In fact, some methods of purifying ores involve heating it to a specific temperature so that one mineral melts while the other doesn’t.
At other times, the melting helps the minerals rearrange into a nice pattern. Diamonds are just carbon in a very organized lattice. Rubies and sapphires, among other gemstones, are just aluminum oxide in a lattice, with their color depending on what other traces of minerals are caught in the lattice when it forms.
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