Why are we told that cold items contract, and hot items expand, but my water bottle expands when frozen?

Answer 1

Very observant - water is about the only thing in nature that expands as it cools & freezes. It's a good thing it does, too:
- if water contracted as it froze like everything else, than each winter every lake & river in cold climates would turn into a solid block of ice. Water would freeze, shrink, and then sink to the bottom. The process would continuously be repeated, and ta-dah!!! No fresh water life left come spring.

Answer 2

Great question.

As the others have stated, water is the exception to the rule. It is "densest" at 4ºC and below that temperature it actually expands again. Frozen water (ice) is less dense than water at 0ºC, and that's why it floats in your drink.

Imagine if this wasn't the case - fish wouldn't live because water would freeze in the winter and the ice would fill the lakes / ponds from the bottom up and thus freeze out the fish!

Answer 3

Water is an exception to that rule. It expands about 7-10% when frozen.

Even though water does expand when heated and contract when cooled at most temperatures, water expands when cooled and contracts when heated between 4 degrees Celsius and 0 degrees Celsius.

Answer 4

Water has interesting thermal properties. When heated from 0°C, its melting point, to 4°C, it contracts and becomes more dense; most other substances expand and become less dense when heated. Conversely, when water is cooled in this temperature range, it expands. It expands greatly as it freezes; as a consequence, ice is less dense than water and floats on it. Because of hydrogen bonding between water molecules, the latent heats of fusion and of evaporation and the heat capacity of water are all unusually high. For these reasons, water serves both as a heat-transfer medium (e.g., ice for cooling and steam for heating) and as a temperature regulator (the water in lakes and oceans helps regulate the climate).

Answer 5

Water is different - it expands when frozen. That's why ice cubes and icebergs float. They have expanded, so are less dense, so float on the more dense liquid water.

Good thing too. If frozen water was more dense, ice would sink (instead of forming a layer on top of lakes). If the ice sank, it would eventually build up from the bottom and all bodies of water would become solid - there would be no life in the lake or oceans(and, extrapolating "backwards", life would probably NOT have evolved on our planet if the ice sank instead of floating!)

Answer 6

Water condenses with falling temperature, until it reaches 39º F. Below that, it expands. Once it gets down to 32º it becomes solid, and continues to expand. This is handy since it makes ice lighter than water at 32º, so it floats. If it sank, the ice would form on the bottom, and the entire body would freeze solid, but the ice acts as an insulator.

Answer 7

Because the water goes through a phase change--it freezes. Ice has a crystalline structure that water doesn't have, and because the molecules have to stick to certain places in the crystal, rather than just go wherever they fit, the ice winds up less dense than water.

Up until the point where it freezes, cold water contracts just like everything else.

Answer 8

Ice is a crystalline structure and water isn't. In H2O the atoms are held together by covalent bonds, but there is still a small charge left on each of the atoms. The result is the molecules form hydrogen bonds between the hydrogen atoms and neighboring oxygen atoms. This is why water forms drops (as in rain drops) or has surface tensions (as in Mosquito lands on water to lay eggs). The actual number of molecules bonded to varies between liquid and solid. When liquid one molecule bonds with 3.4 other molecules, but when solid it bonds with 4 other molecules. This small difference causes the ice to expand. See the link below for a better explanation.

Answer 9

That is because water is the exception to the rule. It does expand when freezing and boiling. The crystal structure that takes place during the freezing process causes this expansion, these little particles push out and there are some voids that allow it to do this.

Answer 10

The water inside your water bottle freezes into ice. The bottle contracts around the immoveable ice, and stretches. If you really think your bottle expands when it gets cold, put it in the freezer empty. It will not get bigger.