When I place a bottle of water in the freezer it will be cold but not frozen. When I open it, it slushes up.?

Question

Why? Is it the barometric pressure change?

Answer 1

swg4fnc,

Yes, it is because of the pressure inside the bottle. When water is placed under pressure, its freezing point is lower than it would be for atmospheric pressure. Since you have the bottle closed and the water is somewhat pressurized, its freezing point is lower than 0 degrees C and your freezer is probably not quite cold enough to freeze the water.

The reason water behaves this way is that ice, the solid form of water, is actually LESS dense than the liquid. This means that ice expands when if freezes. So a good way to think about it is that the water wants to freeze, but because the bottle is filled up with water and closed at the top, the water doesn't have ROOM to freeze. When you open the bottle, you release the pressure, raise the freezing point to ambient temperature, and give the water the room it needs to freeze. That's why it slushes up upon opening.

Answer 2

The water became supercooled, and only crystallized when you disturbed it. Supercooled liquid is a liquid that has fallen below its freezing point (for the given pressure) but has not taken on solid form. It is similar to a supersaturated solution in that it has reached a state that is technically inconsistent with its normal material properties, and it can only maintain it if it is not disrupted in any way. In the case of a supersaturated solution, the excess solute crystallizes and precipitates rapidly under the right conditions.

Answer 3

This is called superfreezing. When water of a certain purity level is frozen and not disturbed, the contaminents (not saying the water is dirty, but all water has some) suspended in it allow for subfreezing temperatures, while remaining liquid. If you open it, or even tap it hard enough, the structure of the water will be disturbed and will start to solidify.