Ice Rink Science: Particles, Temperature and State

Ice Time at the Community Rink

1Every winter, the science club at Lakeview Middle School visits the community ice rink. The rink floor is a concrete slab with pipes running through it. A very cold, salty liquid called brine, at about −9 °C, flows through the pipes. The brine takes thermal energy from the concrete and from the water spread on top of it, and the water freezes into a sheet of ice about 3 cm thick. The ice surface is usually kept near −5 °C.

2Between hockey games, a resurfacing machine shaves off the rough top layer of ice and spreads a thin layer of hot water, at about 60 °C, over the surface. The hot water fills the scratches. Within a few minutes, the new layer cools and freezes into smooth ice. On cold mornings, a little steam can be seen rising from the fresh water.

3Back at school, the club tested what happens when thermal energy is added to ice. The club adviser, Mr. Halvorsen, kept 200 g of ice shavings from the machine in a freezer at −12 °C. He placed them in a beaker on a hot plate and left the hot plate on one setting for the whole test; only he touched the hot plate. Club members Priya and Dario stirred the sample gently and read a thermometer every 5 minutes. Their results are in Table 1.

4The club also left a sealed, empty plastic water bottle by the rink boards. The bottle had been capped tightly in the lobby, where the air was 22 °C. After an hour next to the ice, where the air was about 2 °C, the sides of the bottle had dented inward. When Dario carried it back to the warm lobby, the bottle slowly popped back into shape.

5Scientists use a particle model to explain observations like these. In this model, all matter is made of tiny particles that are always moving. Solids, liquids and gases differ in how close together their particles are and how freely the particles move. Temperature is a measure of the average kinetic energy of the particles.