Supercooling of water-what's going on?

[BuddyPal]

Perhaps you have seen the videos of either beer or distilled/purified water flash freezing. What usually happens is someone has a bottle of water and he hits it on something, then the water in the bottle begins to freeze from top to bottom. Or sometimes someone has the bottle of supercooled water and they pour it over ice in a bowl and the water instantly turns into slushy.

I want to know how the water can supercool, and what effect impurities have on the crystallization of water.

 

[DaveC426913]

I want to know how the water can supercool, and what effect impurities have on the crystallization of water.

By the nature of this last statement, you seem to already know. Is there something specific you'd like clarified?

 

[mgb_phys]

It takes a small amount of energy to make the surface area of the first bit of ice. Even though you are going to release a lot more energy freezing the water you need to get over this initial hump. If there is already a small cavity like a spec of dust or a crack in the container to start from the amount of surface needed and so the energy is reduced.

You can cool water to about -40degC before the cooling becomes powerful enough to form ice anyway even if there are no impurities to start the process.

 

[BuddyPal]

Thanks, that clarifies a lot =)