Why when you evaporate coffee and store the steam until it becomes liquid again, the liquid no longer has the color of coffee?

Question

I did this experiment one day because I was curious, sorry if it’s a stupid question

In: Chemistry

Answer 1

Coffee is a mixture of water and other stuff.

Boiling is when you turn a liquid into a gas by making it hot.

When you heat coffee, the temperature where the water becomes gas (steam) is lower than the temperature where the “other stuff’ in the coffee would become gas.

So the gas you create by boiling it is just the water. The “other stuff” stays behind in the pot and wouldn’t boil unless you subjected it to much more heat. (And even then it wouldn’t raise the temperature high enough until after the water finished boiling away first. In a sense, once a liquid reaches the point where it starts to boil, the job of changing that liquid into gas gets “first dibs” on using the heat energy, so the temperature doesn’t go up until that job is done greedily stealing all the heat for itself.)

This is a common method for extracting the pure water from the other stuff it’s been mixed with. For example, this technique can be used to make drinkable water from saltwater, because the salt is part of the “other stuff” that stays behind and doesn’t become steam.