Above: Image © VisualCommunications, iStockphoto.com

This article was originally published on January 20, 2012. It was last updated by CurioCity staff on July 26, 2016.

When you think of Canadian sports, you probably think of ice hockey. Many consider hockey Canada’s favourite pastime. But have you ever stopped to think about how ice rinks work?

Did you know? As of 2016, the Rideau Canal in Ottawa holds the Guinness World Record for being the largest naturally frozen ice rink in the world.

Water is denser than ice

Most liquids become denser when they turn into a solid. If that were the case with water, you’d never get to go skating on frozen ponds or lakes. The surface would still freeze, but the ice would then sink because it would be denser than the water below. Thankfully, water is actually most dense at four degrees Celsius. It becomes less dense when it's frozen. This is why ice cubes float when you put them in your drink.

Did you know? One effect of hydrogen bonding in liquid water is high surface tension. It’s what allows animals like water striders to walk on the surface of water.

Hydrogen bonding

A water molecule is made up of two hydrogen atoms and one oxygen atom (H20). The oxygen atom of a water molecule will attract the hydrogen atoms of other water molecules. This is called hydrogen bonding.

When water is in its liquid state, the molecules are in constant motion and stay relatively close together. But when water freezes and turns to its solid state (ice), hydrogen bonding forces the molecules into a lattice of hexagons. It’s just like the pattern of a soccer ball. This process makes it harder for the molecules to move and pushes them slightly further away from each other. This is what makes ice less dense than water.

Did you know? Glycol is an alcohol with two hydroxyl groups (OH) that stays liquid even at temperatures below zero degrees Celsius. It is often used in the pipes beneath ice rinks.

Artificial rinks

Natural ice rinks, like frozen lakes, depend on cold weather. However, some artificial outdoor rinks have special cooling technologies that allow you to skate on them even when the temperature is above zero degrees Celsius. These technologies are similar to those used in indoor arenas, refrigerators, and air conditioners.

Electricity powers a compressor that packs the molecules of a gas (like ammonia) closer together until they become liquid. This releases a lot of unwanted heat. This heat is either vented away or used in some other process.

The compressed liquid is then allowed to expand back into a gas. To expand, it needs to take in the same amount of energy (in the form of heat) as it gave off when it was compressed. The gas steals heat from its surroundings, making everything near it very cold.

The chilly gas is then used to cool a liquid that is then pumped through pipes underneath the ice rink. And voila, cold ice indoors or in mild weather!

Learn More!

About the physical properties of water and ice:

Hexagonal ice (ice Ih) (2016)
M. Chaplin, Water Structure and Science

Ice structure (2011)
S. Dutch

Water density
US Geological Survey

About ice rinks:

Michigan Tech ice rink goes green (2013)
W. Frahm, Michigan Tech News

Make your own backyard skating rink
C. Cameron, Live right now

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