Weird Water

What happens to water when it freezes? Do the water particles or molecules get smaller and more dense? Or do they take up more space—that is, expand—when they freeze?

See if you can figure it out by trying this experiment. Fill a disposable plastic bottle with water, put on the cap, and then leave it outside when the temperature is below freezing (or put it in the freezer). As the water freezes into ice, what happens to the bottle's shape and size?

Hint: Water is different from most liquids. Most of them shrink and get more dense when frozen. But water doesn't. It takes up more space when frozen. That is, it expands. How did your bottle experiment maybe prove this?

The Tip of the Iceberg

You've maybe heard people say, "It's just the tip of the iceberg." That means only a small part of whatever they're talking about is clearly seen. And the saying comes from the fact that most of a chunk of floating ice lies below the surface of the water.

Check the ice fact out for yourself! Fill a clear bowl with water. Then add some ice cubes. How much of each cube is above and how much is below the water?

Water's Rising!

Does sea level go up when an iceberg melts? How about when a glacier melts? Try this experiment to find out. Float some ice cubes in a glass of water. Put a rubber band around the glass to mark where the water level is. Then wait for the "icebergs" to melt. Does the water level change?

Now try it with ice that's not floating. Put some ice cubes in a strainer and suspend it above the water in the glass. As your "glacier" melts, what happens to the water level?

Salty or Sweet?

When salt water freezes, it forms freshwater ice. How is this possible? Ice is formed from only water molecules—that is tiny particles made of hydrogen and oxygen. Salt is made of other things. So when salt water freezes, the salt itself doesn't freeze.

Want proof? Mix salt into a clean cup of drinkable water. Put the cup in the freezer or outside on a freezing-cold day. After the water has frozen, take the ice out of the cup. Rinse the ice off with tap water. Now taste the ice. Is it salty or not?

Melt Down

Ice and snow keep the area around them cool. Why? It's not just because they're cold. It has to do with how the sun's rays reflect off of different colors. Dark colors absorb, or soak up, heat—lots of it. But light colors, including ice and snow, bounce the sun's rays right back up to the atmosphere.

If there's snow or ice where you live, you can see this in action.

Gather up some dark-colored sticks, pebbles, or leaves and place them on top of the snow or ice. Check back after a sunny day. The sun should warm up the dark objects more than the light snow or ice around them. So what has happened to the snow or ice under and next to them? And what has happened to your objects? Have they moved or changed position compared to the surrounding snow and ice?

Illustrations by Michael Slack