by Andrew Franz

Created on: February 10, 2009   Last Updated: February 25, 2009

A favorite topic of high school teachers around the country is the physics of sports. They use sports to explain everything from trajectory to torque to momentum to friction. Physics is also the explanation for why hockey pucks are frozen.

A hockey skate does not cut through ice, but rather melts it. The energy from the player's leg transfers to the edge of the skate, creating friction with the ice, melts it and essentially glides on water. One might think the same principle would apply to a warm puck. Unfortunately, the greater surface area of the puck and the material negate this theory.

Pucks are made out of vulcanized rubber (rubber that is superheated and cooled quickly to be stiff and hard). Rubber possesses a high potential for friction, especially when wet. Imagine wearing leather pants and sweating. A warm puck, or even room temperature puck, will heat the ice and halt abruptly from its destined path. However, when a puck is frozen, friction is reduced and the puck slides more regularly.

Also, unlike a skate blade, a hockey puck is wide and flat. When a puck melts the ice, it tends to refreeze quickly. The effect is a puck that looks like a ball rolling in loose sand. It will move quickly for a time then stop. This proves to be a very boring brand of hockey as players move and the puck cannot follow. It can be frustrating, too. Players are used to the quasi uniformity of their on-ice instruments. When they make a pass, or take a shot, they are trusting that the ice is smooth and the puck movement is crisp. An unfrozen puck will put an end to that.

When frozen, the puck will move crisply and with purpose while it's on the ice, but as the game has evolved with curved sticks taking the game to the air, it produces another effect. A bouncing puck, or lively puck, creates a greater risk factor for the defensive aspects of the game. As mentioned earlier, a hockey puck is made of a hard rubber. Unlike rubber on concrete, rubber on ice does not bounce that high. However, when the puck is frozen it ricochets, caroms, and deflects in a million directions. Pucks bounce around defensemen and goalies regularly.

No matter the science behind it, freezing the puck in hockey makes the game more exciting. So the next time you see a player on a breakaway and the puck seems to stick to the ice, you know who to blame (the trainer who forgot to freeze the pucks).

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