in places where the sea freezes over, does the ice contain salt?

Yes, but the pressure of ice on top can force out the salt. The Blue ice you see in larger ice burgs is fresh.

oh ok thanks

icebergs are almost entirely fresh water. The blue ice is ice with no bubbles in it. Icebergs are made from snow, not sea.

 

Sea ice is salty, but usually less salty than sea-water and the amount of salt depends on a number of things.

Isn't it true that sea water freezing slowly tends not to capture salt and the crystal structure of such ice under pressure does not allow for space to hold the salt?

 

The blue nice crystal ice has virtually no salt in it. That is what you want to melt and drink, not the white cloudy stuff, unless it is fresh snow on top.

 

Ice burgs are chunks of glacier, which are of course made of fresh water. I am thinking of frozen sea ice.

Edited January 5, 201015 yr by ajb

As the surface of salt water begins to freeze (at −1.9 °C for normal salinity seawater, 3.5%) the ice that forms is essentially salt free with a density approximately equal to that of freshwater ice. This ice floats on the surface and the salt that is "frozen out" adds to the salinity and density of the seawater just below it, in a process known as brine rejection. This denser saltwater sinks by convection and the replacing seawater is subject to the same process. This provides essentially freshwater ice at −1.9 °C on the surface. The increased density of the seawater beneath the forming ice causes it to sink towards the bottom.

Freezing point depression is a colligative property of water. A colligative property is one which depends on the number of particles in a substance. All liquid solvents with dissolved particles (solutes) demonstrate colligative properties. Other colligative properties include boiling point elevation, vapor pressure lowering, and osmotic pressure.