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20

Do you want to learn about ice?

posted on
Do you want to learn about ice?

It can be slick. It can be beautiful. It is less dense than water (more on that later). It is a major part of one of the most successful children's movies of all time.

Ice.

So, in honor of the release of Frozen 2 on November 22, we thought we'd share a few factoids about our favorite frozen object.

Why does ice float instead of sink?
Frozen water is less dense than liquid water because as water freezes, the hydrogen bonds connecting different water molecules line up to keep the negatively charged oxygen atoms apart, creating equal spaces between the molecules, freezing the water in a lattice-type formation. This results in a change in density that allows ice to float.

If this were not the case, ice would sink when it was formed and go to the bottom of all the lakes, ponds and reservoirs. Even icebergs would sink to the bottom of the ocean. When spring came, not enough heat would get to the bottom to melt the ice down there. So, after a while, almost all the water on the earth would be frozen, and life as we know it would not have developed on the planet.

How do ice skates work to allow the skater to glide over the ice?
A thin film of liquid water covers the surface of any body of ice. How thick the liquid layer is depends on the surface temperature—the colder the ice, the thinner the layer. An ice skate blade bears the weight of the skater on a very small area, and when the skate blade passes over the ice, the increase in pressure and kinetic friction raise the temperature and melt the ice under the blade, creating an even thicker layer of water that has little resistance to the ice skate blade.

Commercially made ice is stirred as it is being frozen; household ice is not. Without mixing, many more ice crystals form, and air is trapped in the ice. Light rays are distorted by these crystals and air, and this distortion gives home-frozen ice a cloudy appearance.

Why do ice cubes bulge from the top of the ice cube tray?
Unlike most things, which get smaller when they get colder, water gets bigger (expands) by 9 percent when it freezes. Because an ice cube tray has a bottom and four sides that don’t move, ice bulges out of the open top when the water expands.

Also, because ice is expanded, it is less dense and lighter than water. So, in the winter, ice floats on the surface of a water body while the water underneath stays liquid, providing organisms, including fish, with a place to survive during the cold weather.

We could ramble on and on about this. We’ll let it go, for now. For additional similar information, please consult AWWA’s Plain Talk about Drinking Water.

We’ve got a sudden urge to build a snowman.

Illustration credit: hend youssef/Shutterstock

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