If water freezez at 0 degrees, then how come some water dosen't freeze at minus -15 degrees?

Question

the freezing waters dont freeze! below 0c

Answer 1

pure water freezes at 0, but many salts and other particles can lower the temperature at which the water freezes.  

Answer 2

The surface will freeze, but the lower layers will still have heat trapped, so they are less likely to freeze up.

Also, if a container of completely pure water is cooled slowly, it is possible to "supercool" it, meaning the temperature goes below the freezing point, but the liquid does not freeze. A small disturbance, such as touching the surface, will cause the water to freeze immediately.

Answer 3

The surfaces of lakes freeze and trap a small amount of heat in the lake.  If the lake is shallow enough, such as a pond, it will indeed freeze solid.  Rivers and flowing waters trap heat but also generate a minute amount of heat with the action of the moving water.  They can flow at very close to zero C.  Ocean waters, such as the artic, are salty and remain liquid below zero C.

To answer your question, plain water does freeze at -15 degrees.

Answer 4

Antifreeze is a cryoprotectant used in internal combustion engines, and for many other heat transfer applications, such as electronics cooling and chillers for HVAC. Compounds are added to water to reduce the freezing point of the mixture to below the lowest temperature that the system is likely to be exposed to, and to inhibit corrosion in cooling systems which often contain a range of electrochemically incompatible metals (aluminum, cast iron, copper, lead solder, etc.).

The term colligative agent may better describe the benefits of these compounds in warm climates, since they not only achieve freezing point depression in the winter when mixed with water, they coincidentally achieve boiling point elevation of water. Colligative agents are properly referred to as both antifreeze and "anti-boil" when used for both properties. The term engine coolant is widely used in the automotive industry, which covers its primary function of conductive heat transfer.

Answer 5

It can depend on movement of the water, salinity or other mineral content, and on sunlight.  I've seen things like ice cream melt outside at -27 because it was in direct sunlight, so it would be reasonable to assume that sunlight can affect water as well.