Does the density of water increase or decrease upon freezing?

Answer 1

A nice question. When sea water is frozen slowly, the fresh water part freezes first, for it has a higher freezing point. And the salt particles are dissolved into the sea water, making it more saline. For the salt crystal cannot easily fit into the ice crystal matrix.

Thus sea ice is largely fresh water, though there will inevitably be a small contamination by salt.

[An analogous process is used in zone refining of materials where a solid rod of material has a melt zone passed along it by a special heating system. This gradually moves the impurities along to the end of the rod. Once again, the impurities cannot easily fit into the new crystal matrix.]

Answer 2

The freezing point of a solvent (water, for example) changes if you add solute to it, making a solution. The new freezing point is equal to -1.86 x the molality of the solution. Molality is moles of solute (salt) divided by kg of solvent (water). But if the solute is an ionic compound that dissociates in the solvent, then you multiply by the number of ions formed. Salt dissociates in water into two ions, one Na+ ion and one Cl- ion. So the freezing point of salt water is -1.86 x 2 x the molality of the salt water. The number -1.86 applies only to water.

Answer 3

You will notice at the opposite poles of the globe large sheets of ice. This is primarily sea water that has frozen. Oddly enough, the ice at the poles is fresh, that is non-salty. Salt lowers the freezing point of water, but does not prevent it. The water crystallizes on the near molecular level, steadily pushing the salt in solution lower and lower. It helps that salt water is more dense than fresh water, so fresh water rises to the top, where it freezes more.

Look, anyone who lives in the states and countries where it snows regularly, knows that salt only slows down the freezing process. Road crews put salt on roads only to the 25 degree Fahrenheit level. Below twenty-five degree level, salt is no longer effective at removing or preventing ice from building up on roads. Ice and salt at very cold temperatures make slush or slurry. Eventually it freezes.

Answer 4

It increases, when salt water evaporates, it leaves behind the salt. Which then increases the amount of salinity.

Answer 5

yes. the higher the salinity, the colder it has to be to freeze.

Answer 6

Salinity is increased by evaporation or by freezing of sea ice. It is decreased as a result of rainfall, runoff, or melting of ice.

Answer 7

Salt decreases the freezing temperature, making it more difficult to freeze.

Answer 8

Yes