http://www.ck12.org Chapter 2. Matter
2.18 Freezing
- Describe what happens to the particles of matter when it freezes.
- Define freezing point, and state the freezing point of water.
The man in this photo is climbing a glacier. Ice climbing is a dangerous sport that should be attempted only by
highly experienced climbers. For one thing, ice is very slippery, which makes it harder than rock to grip. Clinging
to the slippery vertical surface takes strength, training, and the right equipment.
From Liquid to Solid
You don’t have to be an ice climber to enjoy ice. Skating and fishing are two other sports that are also done on ice.
What is ice? It’s simply water in the solid state. The process in which water or any other liquid changes to a solid is
calledfreezing. Freezing occurs when a liquid cools to a point at which its particles no longer have enough energy
to overcome the force of attraction between them. Instead, the particles remain in fixed positions, crowded closely
together, as shown in theFigure2.38.
Freezing Point
The temperature at which a substance freezes is known as its freezing point. Freezing point is a physical property of
matter. The freezing point of pure water is 0°C. Below this temperature, water exists as ice. Above this temperature,
it exists as liquid water or water vapor. Many other substances have much lower or higher freezing points than