Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Phase Changes of Water

  1. Jul 20, 2003 #1
    If there is a pool with a depth of 10 ft and a lake with a depth of 10 ft, and the air temperature is below 0 degrees Celsius, which one will freeze first, and why? The lake will form a sheet of ice on top, but will the pool do the same? Can you solve for the thickness of the sheet of ice without knowing the surface area of the lake itself?
  2. jcsd
  3. Jul 21, 2003 #2


    User Avatar

    10 ft of water is 10 ft of water in this case, neglecting the percentage of salts and other things that vary chemically w/n the two bodies of water they should freeze at the same time.

    They both will form a sheet of ice on the top 1st. This has absolutely nothing to do w/ where the water is contained (lake or pool). The reason it freezes on the top 1st is b/c of water's exhibits a very unique property. When most things solidify they tend to get more dense, matter taking up less space, however water does not share this property, it gets less dense b/c it organizes in a manner that takes up more space then as a liquid, thus water is more dense as a liquid. More dense state goes to the bottom of the container and the less dense states move upward.

    Figuring out the surface thickness I'm not sure of. I do know that in order to freeze the surface of water the temperature of the entire body must be 4 degrees celsius otherwise the sheet of ice on the surface will sink to the bottom warm up and melt while a new sheet of ice forms and repeats the process over and over until the water reaches at or below 4 degrees celsius. Again the sheet sinks b/c of density factors.

    So, IF THE BODY OF WATER is zero degrees celsius then the water will freeze, an air temperature of zero degrees I don't think will give us a clue as much as the water temp., I may be wrong on that one though. Hopefully I haven't steered you wrong but there's more details if you need them.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook