Keeping the Rink on Ice

Do you play ice hockey? Do you skate? Many Canadians would say yes. Even if you said no, you might have seen an ice sport on TV. But have you ever wondered how ice rinks stay frozen?

Did you know?

As of 2019, the Rideau Canal in Ottawa holds the Guinness World Record for longest naturally-frozen ice rink. It is 7.8 kilometres long.

Why does ice float? 

A scientist named John Dalton suggested a theory called atomic theory. Tiny particles called atoms make up all matter. This theory tries to explain how atoms interact with each other. He based the atomic theory on several laws. For example:

• The Law of Conservation of Mass states that matter can not be created nor destroyed
• The Law of Constant Composition states that all atoms of a specific element have the same properties and mass

He used this knowledge to determine two things:

1. Compounds are made up of combinations of two or more types of atoms
2. A chemical reaction is a rearrangement of atoms

The three most common states of matter are: solids, liquids, and gases. The atoms of most solids are packed together more densely than those of liquids or gases. This is one of the reasons why solids can maintain their shape. On the other hand, liquids and gases can flow, or be poured. 

Most liquids become more dense when they change from a liquid to a solid. Denser materials usually sink when you place them in a less-dense material. For example, if you throw a copper penny into a fountain of water, it will sink. That’s because the penny is denser than the water. 

Can you think of one solid this does not apply to? Hint: Think back to the beginning of this article.
If you said ice, you’re right!

If ice were denser than water, you’d never get to go skating on frozen ponds or lakes. The frozen water would become denser than the liquid water and sink below the surface. Luckily for us, liquid water is most dense at about four degrees Celsius. It becomes less dense when it becomes a frozen solid. This is why ice cubes float when you put them in your drink!

What are the two types of skating rinks? 

There are two main types of skating rinks. One type has naturally frozen ice from cold temperatures. The Rideau Canal in Ottawa is an example.

The other type has artificially (or mechanically) frozen ice. The hockey and skating rinks you see on TV are examples. Do you have an indoor skating arena in your community? That’s an example of an artificially frozen ice rink, too.

The first artificial ice rink in Canada was built in 1911 in Vancouver, British Columbia. It was built by two brothers, Lester and Frank Patrick. Artificial ice quickly made its way to Toronto in 1912. By 1920, there were four artificial ice rinks in Canada. 

Did you know?

The earliest record of an organized indoor ice hockey game is a game on March 3, 1875 at the indoor Victoria Skating Rink in Montreal, Quebec. Chilly winter temperatures kept the rink and the spectators cold! 

How do you keep an ice rink cold?

An artificial ice rink is a complex piece of engineering. There is a lot going on under the ice that we cannot see. 

Underneath the ice or ‘skating surface’ (A) is a large concrete floor. It is also known as the ‘ice slab’ (B).  The ice slab contains hundreds of metres of pipes (C). Brine (salty water) is pumped through these pipes. The concrete floor sits on a layer of insulation (D). This layer allows the ice to expand and contract as necessary. When the ice expands, the atoms move further apart. When the ice contracts, the atoms move closer together. Underneath the layer of insulation is a layer of heated concrete (E). This layer prevents the natural contraction and expansion of the ground from cracking the layers above. The entire structure sits on a sand and gravel base (F). This base contains a groundwater drain (G).

So how is the ice made? First, the brine in the pipes cools the concrete base. Brine is water with a high amount of salt. Brine can be cooled to lower temperatures without freezing. It keeps the rink’s ice at a cool -4 degrees Celsius. 

Once the concrete base is cold enough, water is added in layers. This action is called flooding. Once the base of ice is completely frozen, the hockey markings are painted on the ice. These markings might include lines, team logos, and advertisements. Finally, the rink is flooded with several more thin layers of water to protect the paint.

But what if that indoor space is used for another sport? Well, you can remove the ice by pumping hot brine through the same pipes that pumped cold brine. This makes the ice covering the concrete base melt.

As you can see, there’s a lot of physical chemistry behind the ice that we skate and play hockey on!