What temperature does salt water freeze?

Answer 1

Salt causes water to freeze at a lower temperature. In fact, any substance dissolved in water lowers its freezing point. The oceans do not freeze (except in extreme polar areas) because of the salinity (i.e. concentration of salt). When you do see ice in the ocean, it is actually frozen fresh water that has risen to the surface.

Answer 2

when salt dissolves in water, its sodium,chlorine ions leave the the salt crystal and mix separetly among the water molecules. resuling that salt is like a acid it takes longer (Icebergs do not form from salt water, however. They detach from frozen fresh water glaciers formed over many years by the freezing of compacted or melted snow.)

Answer 3

Salt is effective to temperatures of 20 degrees at which it takes 20 minutes to begin melting the snow. Below 10 degrees its useless by itself. They usually mix it with calcium chloride and this enables to use it to temperatures well below zero. It can be effective at temps of -40 to -50 degrees.

The sea water freeze at approx. 28 degrees Fahrenheit (between -2 0C and -3 0C).

The freezing point of salted water (with NaCl) depends on the concentration of the sodium chloride. The minimal temperature possible (-21,1 0C) is at a concentration of 23,3 % NaCl.

Answer 4

The process of freezing occurs when H2O molecules moves slower and slower until some of the molecules lose enough energy that they get "stuck" to other water molecules. The stuck together bunch grow larger as the solution loses more energy in the form of heat and grow as Ice. H2O has a special bent shape and ice crystals are formed from ordered hexagonal shapes in a lattice see related link 1.

But when salts are dissolved, it introduces positive and negative ions floating with the water molecules. These ions attract water molecules are around them and cause an increase in the disorder (entropy) of the water molecules bumping around making it harder for the water to slow and get "stuck". This is why salts are added roads in the winter to stop ice forming.

Eventually, when the solution is cooled even lower, ice will begin to form, but ice is so crystalline and ordered, the ions positive or negative cannot fit into it easily spaces between water molecules. So any ice that forms in the salty solution will be mostly pure water, leaving the rest of the solution saltier as it loses thermal energy. Interestingly this is also why; you can drink melted icebergs even though they are formed from salty undrinkable sea water or conversely why if you accidently freeze a can of coke, the liquid that comes out is nearly as concentrated as coke syrup.

if the temperature continues to drop, the remaining solution will be so salty that it cannot form anymore ice. What you end up after the temperature drop well past the new freezing point, is grains of ice made of pure water in a saturated salt water solution. see note below.

Surprising, this resembles what happens when metal alloys are formed and relates to a branch of science called material science. The ice grains can be called one "phase" and the sat. salt solution can be called another "phase" much like the terms are used in that branch of science. see related link two for a picture of different phase grains in an alloy.

This was a surprisingly complex process to explain adequately, I hope it is not overly difficult to understand. if you are interested crystals and material science at a university level, I'll suggest the following articles to read up on

Crystal structure
http://departments.kings.edu/chemlab/vrml/lattices.html

phase diagrams
http://www.chm.davidson.edu/vce/PhaseChanges/PhaseDiagram.html

alloys (made by a dentist but gives a good intro)
http://www.doctorspiller.com/dental_alloys_2.htm

Note. The beautiful answer above misses two points.
The assertion that you end up with ice grains is true of salt water in a laboratory, but not of the sea on our planet. Temperatures below 0 C are not found in most of our oceans, and seawater is nowhere near saturated.
It should be mentioned that when water freezes it expands; ice has a slightly lower density than water, which is why icebergs float.

Answer 5

the range of temperature for freezing of salt water mixture is -20 to -23 deg cel.

called as eutectic temperature.

Answer 6

it freezes at a lower temperature than pure water.

Answer 7

Surely you're aware of the north polar ice-cap,

which is an extension of the Arctic Ocean.

Answer 8

It expands just like unsalted water does. It just does it at -10oC rather than 0oC.

Answer 9

you put the saltwater in the frezer for a day the next day take it out