Freezing Solutions

When you freeze some liquids,some times, some of the liqude seperates from the ice.Why and how does this happen?
- Matt (age 13)
Edwards Middle, Boston,MA,Massachusetts

For any freezing liquid, there's a period when part of the liquid is frozen and part isn't. I'm guessing that you're asking about something more specific, the effects of freezing solutions of water and other chemicals, like salt or sugar or alcohol. When the ice starts to form, it consists of almost completely pure water molecules arranged in a regular crystal pattern. That leaves a liquid which has a higher concentration of solutes (say salt) than you started with. Ice forms from that more concentrated solution only at a lower temperature than from the initial solution. If you’ve left the solution in a moderately cold freezer, some ice will form but at some point the leftover solution will be too concentrated for more ice to form. We have lots of related answers, which you can find by searching this site.

Mike W.

(published on 10/22/2007)