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Facts on Winter Water
from Ducks Unlimited's Puddler magazine Summer 1998
In winter time, many areas of North America turn into frozen, white wonderlands. What works this magic? Water! When the temperature drops, water changes form. It freezes from a liquid into solid snow and ice. You can see snow and ice covering the ground, hanging as icicles, frosting over windows, and coating rivers and lakes.
Water looks different when it is a solid. It no longer flows. Instead, it locks into beautiful patterns. Frozen icicles glitter like glass decorations. Frost on windows looks like white lace. Drifting snow turns trees and houses into soft, rolling shapes.
Solid water also "acts" differently. These differences have important effects on the land and on living things. They also make water one of the earth's most unusual materials.
Frozen water builds beautiful shapes
Water and all materials are made up of tiny parts called molecules. When water is a liquid, its molecules are able to move around, and it can flow. When water freezes, its molecules stop moving. They join together in repeating patterns called crystals (you can think of these patterns as something like jungle gyms).
An ice cube is made up of crystals and so is a snowflake. Ice crystals that form inside clouds bump into each other and stick together. They grow into snowflakes. All snowflakes have six sides, but no two snowflakes look exactly alike. They are one of Nature's most beautiful decorations.
Frozen water floats
When water freezes into a solid, its molecules spread out to form crystals. The molecules are not "packed together" as tightly as they were when they were a liquid. As a result, solid water is less dense than liquid water. Density measures how "tightly packed" molecules are inside a material. Any material that is less dense than water will float in it. Since ice is less dense than water, it floats, too!
If ice did not float, wetlands and other watery places would be in trouble during cold weather months. As their waters froze over, the ice would sink to the bottom and pile up. All life in those waters would be killed. Instead, deep ponds and lakes form a layer of ice that floats on the surface. Fish and other creatures can continue to live in the waters below.
Water is one of the only materials that is less dense as a solid than as a liquid.
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As water freezes, its molecules spread further apart to form crystals. This means the molecules take up more space. When water freezes, it "grows" or expands. Expanding water can "push" on things around it with great force. For example, water trapped in rocks and cement freezes during cold winter weather. It can expand with enough strength to create cracks! In this way, winter water actually helps break down rocks into smaller pieces over time. It also helps create "potholes" in roadways. When water inside plant cells freezes, it also expands. The plant's cell walls burst open, and the plant dies. And when humans get frostbite, their cells freeze and die. Water is one of the only materials that takes up more space instead of less space when it
becomes a solid.
See for yourself!
Try the activities that follow to see how solid water looks and acts.
Check out water's different densities
You'll need: drinking glass, water, cooking oil, ice cube
1. Fill a drinking glass halfway with water. Drop in an ice cube. What happens? Can you make the ice
cube sink?
2. Remove the ice cube from the glass. Fill the glass the rest of the way with cooking oil. What happens? What does this tell you about the density of the oil compared to the density of the water?
3. Drop the ice cube into the glass. What happens?
4. Use a piece of tape to mark where the water and oil meet. Wait for the ice cube to melt. What happens to the water level? What do you think happened?
Watch water expand
You'll need: empty plastic soda bottle, aluminum foil, water
1. Fill the soda bottle with water all the way to the top.
2. Cut a piece of aluminum foil to make a 2-inch square. Place the foil loosely on top of the bottle.
3. Place the bottle in the freezer. Wait for the
water inside it to freeze. What happens? Why do
you think so?