How fast freeze water
Water freezes at a temperature of 0 degrees Celsius. Suppose you urgently needed for some ice purposes. How to get it? It would seem easier: you just have to cross between the vessel with the liquid in the freezer. But the water, due to the very high specific heat, cools slowly, and ice formation may take a long time.
Instruction how fast freeze water
Freezing rate depends, firstly, on the heat exchange surface area, and secondly, the thickness of the water layer: what it is, the slower will freeze the entire volume of water (and vice versa). Therefore, pour water into the container such that the cooling surface is large enough, and the thickness of the water layer - small. You can use, for example, the Lednice - plastic substrate with small and shallow containers that produce specifically for this purpose - getting food ice at home. Put a bowl of water in the freezer. Ice is formed much faster than in case if exactly the same amount of water was poured into a plastic cup, for example.
Furthermore, it is possible to accelerate the freezing of the water as follows. When the temperature is already close to 0, toss in each container odnu- two grains of salt. It would seem a paradox, because we know that salt water freezes at a lower temperature than fresh water. But the paradox is only apparent: the mass of salt will be so negligible that the water actually remain fresh and grains serve as a kind of initiate crystallization.
If you have a long thin container types of tubes (steel only), you can very quickly get the ice with the help of liquid nitrogen. Lower the water container (with a long clamp or wire) in a Dewar vessel, of course, not completely to liquid nitrogen it is not filled. After some time, remove. Once the vessel wall will heat up, the ice can be removed easily.
Can be used for quick freezing property of certain chemicals to dissolve, absorb large amounts of heat. For example, there is substance - ammonium nitrate (ammonium nitrate). It is widely used in agriculture as a nitrogen fertilizer. If the ice that you want, is not used for food purposes, add the ammonium nitrate directly in the tank with cold water and dissolve, stirring. Then he put the container in the freezer. Ice forms in minutes.