Why does hot water take dirt off dishes so much easier than cold water?
In: Chemistry
To understand this, we need to talk about molecules. Molecules are the smallest thing that’s still the same thing. You can divide a cup of water in half, and the two halves will still be water. If you cut a water molecule in half, you don’t get two even-smaller waters. Molecules are tiny. Molecules in liquids and some solids tend to slightly stick to each other. Sometimes one molecule will have parts of it that are friendly with one kind of other molecule and a different part that’s friends with a completely different kind. Soap is like that. It’s friends with both water and fat.
Let’s say that there’s a plate (ceramic) molecule and their friend, a fat molecule. They’re holding hands but you want to break them up. Should you send them to a ballroom (cold water) or a mosh pit (hot water)? People move a lot faster and more violently in the mosh pit, so that’s the best bet. In the same way, the molecules that make up fat are pulled away by hot water, whose molecules are vibrating faster than cold water’s. Water isn’t very friendly with fat though, so hot water alone doesn’t work great. It works even better if fat’s clingy, moshing friend, the soap molecule, grabs a hold of both the moshers and fat and pulls them away into the crowd.
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