Neighborhood Nature

Our Family's Nature Blog

First Hard Freeze for Our Jars of Water December 7, 2009

Filed under: Experiments,Fall,Geology,Puzzles and Mysteries,Seasons,Water,Winter — saltthesandbox @ 10:22 pm
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Back on November 29th we started an experiment on our front porch, with four plastic jars filled with water. At the start of the experiment, the jars looked like this:

Water jar experiment, Day 1, November 29, 2009

Here's what the experiment looked like five days ago, before the temperature hit the freezing mark.

Now, here’s what the experiment looked like on Friday, December 4th, after the air temperature went below freezing, hitting 24 degrees Fahrenheit overnight:

Water jar experiment after a hard freeze, December 4, 2009.

Here's what the water jars looked like after a hard freeze. Three of the five jars had frozen overnight: A, B, and D. Also, we had added a fifth jar: In Jar E, the water that had been BOILED first, then cooled, put in the jar, and sealed with a lid that had NO holes in it. (Thanks to J of Science Museum of Minnesota for suggesting this addition to the experiment.)

Three of the jars had frozen water in them, including the jar with SALTY water. No one predicted that! The two jars that did not freeze were both sealed tight — there were no holes in their lids.

Here’s a closer look at Jar A, which started out as cold, fresh tap water, and was covered by a plastic lid with holes drilled in it:

Jar A (fresh water, started cold, holes in top), Decmber 4, 2009, 24 degreees F

A closer look at Jar A shows intersecting sheets of ice, more densely frozen closer to the top of the jar.

Jar B showed a similar pattern, although the sheets of ice were more horizontal than vertical:

Jar B (fresh water, started warm, holes in top), Decmber 4, 2009, 24 degreees F

Jar B also had sheets of ice, more densely frozen towards the top of the jar -- but the ice sheets were more horizontal than vertical.

Jar D was most surprising. I was expecting the salty water wouldn’t freeze, but the top part of the jar was frozen fairly solid. However, the bottom of the jar was not frozen, but had a bunch of bubbles sticking to the side of the jar:

Jar D (SALTY water, started cold, holes in top), December 4, 2009, 24 degreees F

In Jar D, notice the clear division between frozen water above and unfrozen water below.

So, that leaves us with two mysteries to solve:

  • Why did most of the water in the salty jar freeze?
  • Why did the water in the sealed jars not freeze?

I have some ideas, but I won’t tell you about them yet. However, I will give you one hint about the second mystery. Here’s what the lower part of salty Jar D looked like on December 2, 2009 — three days after the experiment started, but before the temperature dropped below freezing:

Jar D (SALTY water, started cold, holes in top), December 2, 2009, 37 degrees F

Here's what Jar D looked like three days after I had mixed in several handfuls of sidewalk salt, but before the first hard freeze. How can this help us understand why the top of the jar froze, but the bottom did not?

Feel free to tell us your ideas in the comments section (below) or on Facebook.

 

5 Responses to “First Hard Freeze for Our Jars of Water”

  1. J. Newlin Says:

    Hi Eric,
    Have you been thinking of the availability of nucleation sites? I’m wondering how cold it had to be before Jars C and E froze solid.
    J.

    • Hi, J,

      About a week ago the temperature here got down to 2 degrees F, and all the jars froze except the bottom of the one with saltwater (D). C and E froze after A and B, through, and the ice was clearer. I’ll post photos and commentary once I get caught up with Christmas Bird Counts and other birding related responsibilities.

      Eric

      • J Newlin Says:

        Hi Eric,
        Thanks for your note. I’m not surprised.
        My hypothesis is that ice forms most easily around nucleation sites — provided by salts, impurities and dissolved air molecules. So ice begins to form in the salt water, attracting only pure water molecules. The ice crystals then float to the top, leaving the bottom of the jar with a more concentrated salt solution. The reason that the warm water and boiled water froze later is that most of the air molecules have been removed by heating. I wonder if the holes/lack of holes in the lids make much difference.
        Hope all is well with you and your family. Happy holidays!
        J.

      • Overall I like your thinking!
        But I think the holes/no holes did make a difference, because B started out just as warm as C, but had a lid with holes, open the the air. B started freezing before C. Given your nucleation hypothesis, the water in B probably dissolved at least some gas molecules as it sat, exposed to the air, for several days before the temperature hit freezing.
        Of course, we could also advance a pressure hypothesis: Maybe C and E did not freeze because they were completely full and confined by lids. Doesn’t water expand (or try to expand) as it freezes? Could higher pressure prevent freezing? Just a thought….

  2. ryan Says:

    The 3rd jar didn’t freeze because without holes, essentially, it was insulated, so it would take a long while to bring all the water down to below the freezing point. It had nothing to do with pre-boiling. If you put out a saltwater jar with no holes, it would take even longer to freeze.

    Anyway, I hope you keep posting to your Columbus Park nature blog. I like it. I’m getting married there soon.


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