Why Does Ice Float?

It’s really hot outside and you go into the house to get something cold to drink. You get your favorite cup and put in some ice. Then you fill it with your water favorite drink. You may not notice, but the ice is floating at the top. You might think “duh, it always does that”. But did you know ice floating is really unusual? Water is one of the few substances that expands when it freezes. Only a few rare metals can do that. 

So what’s the big deal? Well, if ice didn’t float, life would probably cease to exist on our planet. Imagine a lake where the ice sinks after it freezes. Ice actually acts like insulation and helps keep the water down below from getting colder.  Without an ice layer,  water can keep getting colder and colder and the lake would freeze all the way down. All the fish and plants would die.

In the ocean, ice that freezes on the surface is actually fresh water. If it sank, fresh water would keep sinking to the bottom and the ocean would get saltier and saltier until nothing could live in it. 

So how does ice expand? When water is a liquid, the molecules can slide past each other up close. But when it freezes, it forms a crystal structure. Imagine you have a bunch of friends over. How many can you get in your room? Probably a lot. But what if you had to join hands with your arms straight out? This is kind of like a crystal structure. Now you can’t fit as many in the same space. Density is how much matter (or friends) you can fit in a certain space. The less friends, the less you all weigh. If you weigh less but take up the same space you would be less dense and would “float” (well, if you were ice).

If this is still confusing, that’s ok. Even high school students get confused over it too. Maybe this site can help. 

https://www.thoughtco.com/why-does-ice-float-604304

Ok, now I’m thirsty. Time to go get a cold bottle of water! 

Love,

Papaw