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Q & A: Freezing liquids expanding

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Most recent answer: 12/12/2013
Q:
Im doing an experiment with 10 different liquids. (juice, egg beaters, marinade, soy sause, worchestershire sause, V-8, Mr. Pibb, boost, syrup, twister juice). I put them in the freezer and had to determine which liquids expanded, contracted or stayed the same. What causes a liquid to expand? What causes the liquid to contract? I had some liquids that didnt freeze, they were mostly sugar and salt liquids.
- Cali
Hillcrest Elementary, Lawrence Kansas
A:
Hi Cali,

It sounds as if you have picked a delicious lineup of liquids to test! Yum.

When a substance freezes, the molecules slow down and settle into a rigid regular pattern. In the process, most substances take up less space when frozen than when liquid. Water is a very important exception -- in its crystalline state, ice, it takes up more room than the liquid water did. In an ice crystal, the special way that the different water molecules touch happens to take up more room than when they cram together in a liquid.

Most, if not all, of the liquids on your list consist almost entirely of water (the syrup may have so much sugar in it the water is less important). Most of your liquids are not really substances, but are mixtures of different kinds of molecules dissolved or otherwise suspended in the water. Mr. Pibb also has dissolved carbon dioxide gas which almost certainly bubbled away when it froze (the solubility of C02  is less in ice than in water), although bubbles may have been frozen into the ice it made, making it bigger in a rather uncontrolled way. It might be best to let all the carbonated liquids go flat before doing the experiment. My guess is that all of your fluids should have expanded when frozen because the water in them does, but the effect may go away if most of the liquid is not water.

If you dissolve something like sugar or salt in water, the freezing point will be less than that of pure water -- please search this site for an explanation of why this is.If you have enough stuff dissolved in the water, the resulting mixture may not freeze at the temperature of your freezer. Once some of the water starts to freeze, the leftover liquid will have even more concentrated sugar or salt, so it will be even harder to freeze. So you may be able to freeze some of your liquid, leaving behind some very concentrated stuff that won't freeze except when it's colder than your freezer.

Tom (w mike)

(published on 10/22/2007)

Follow-Up #1: freezing point depression

Q:
Why is it that if you dissolve something like sugar or salt in water, the freezing point will be less than that of pure water?
- Anonymous
A:
Nice question.

The ultimate factor that determines what is stable ( liquid vs. solid, etc.) is entropy: a measure of how many states look which way

Sugar molecules and salt ions do not fit at all well into the regular ordered pattern of water molecules that make up an ice crystal. So when ice starts to form, they stay behind in the liquid. Every water molecule that joins the solid leaves less room for the sugar or salt molecules to wander around in the liquid. That means the entropy of those solutes is reduced when the solid forms. Since the stable form is the one with the bigger net entropy (counting all the relevant entropies) having solutes in there favors the liquid over the solid. That means you have to get it a little colder before other terms, favoring the solid over the liquid at low temperature, win.

Mike W.

(published on 10/22/2007)

Follow-Up #2: freezing soda can

Q:
I"m doing a science project that goes as follows: Problem; If a 12floz can of soda is placed outside at about freezing temperature will it implode or explode? Hypothesis; I hypothesise that if I put a 12floz can of soda outside at about freezing temperature it will implode because according to Charels Law if the temperature decreases the pressure will decrease. Will this law (Charels Law) still apply when there is water and carbonation with other compounds, solutions, mixtures, and elements in it too. (because water expands, but the other components contract)
- Lexi T (age 14)
Reno,Nevada,United States
A:
The best way to answer this question is to do the experiment. Meanwhile, I can make a guess.

Two things make the contents expand and/or increase pressure.
1. The water expands as it freezes.
2. CO2 is expelled from the ice, adding to the amount of gas.

One thing has the opposite effect.
3. Gases have lower pressure at lower temperature.

Since the can is almost filled with liquid, I expect that the expansion is much more important.
If you had a similar can that was not so filled up, you might get the opposite result.

Mike W.

From my own experience I remember that while the cans dont explode they bulge out as if they were trying to. But as Mike advises, "Do the experiment".  There is nothing like first hand evidence.

LeeH


(published on 12/07/2007)

Follow-Up #3: Freezing temperatures of different liquids

Q:
Im doing a project and it deals with the following: do all liquids freeze at same temperature? I use eggs w
- dalanno (age 14)
phila pa
A:
In general, different liquids have different freezing temperatures.  Water, of course, freezes at 0 degrees Celsius.  Pure ethyl alcohol freezes at about -117.3 Celsius.   Nitrogen is a gas at room temperature but will turn into a liquid at  -195.8 C.  Keep on lowering the temperature and it will freeze at -210.0 C.  That's pretty cold, only 63 above absolute zero.

LeeH

Eggs are complicated because, even if you only pay attention the the whites, they have several different molecular components. They'll start to freeze at one temperature, then more will freeze as the temperature is lowered further. I bet that if you do this carefully there will be several different types of crystals formed, not just one type.  Mike W.

(published on 01/02/2008)

Follow-Up #4: CO2 in H2O vs. temperature

Q:
wouldn't the solubility of carbon dioxide (and any other gas, for that matter)increase, rather than decrease, at lower temperatures?
- Anonymous
Philippines
A:
You're absolutely right. We screwed up. It's fixed now.
Thanks!

Mike W.

(published on 04/26/2009)

Follow-Up #5: partly frozen jam

Q:
I recently discovered in my freezer that a redcurrant jam which I had frozen so as to use 50% less than the recommended 1 kg sugar to 1 kg fruit was not actually frozen. It moves sluggishly when tilted. From your previous explanations that the sugar is displaced by the freezing water molecules I can understand the phenomenon, but is the Jam preserved OK if it isn't actually hard frozen? It is a year old! Thanks for the expertise... Peter
- Peter Wilkinson (age 61)
France
A:
As you've probably gathered from our earlier answers, ice crystals formed in your jam, leaving an even higher sugar concentration in the remaining liquid. That lowers its freezing point even further. An ordinary freezer doesn't get cold enough to freeze ice from a saturated sugar solution, so you're left with some highly concentrated sugar solution.

Will the combination of low temperatures and high sugar concentration be enough to make your jam safe after one year? It would be unsafe (because University lawyers would kill us) for us to answer that question. The answer may depend on what sorts of bacteria etc. were present to begin with. I would consult a food scientist.

This reminds me of my experience canning mulberry preserves as a graduate student. Like you, I used relatively low sugar, and the preserves were delicious. One friend came through town on the way to his sister's wedding, which had a color theme of "white". The jar of deep-purple homemade preserves exploded in the living room shortly before the reception was to be held there. Fortunately, no one had eaten any and my friend, miraculously, also survived the interaction with his sister. After that I only made frozen preserves, but never kept any for a year.

Mike W.

(published on 08/22/2011)

Follow-Up #6: freezing jam

Q:
Hi, I think I got why jam doesn't freeze. My question is: will jam freeze if we use a "super fridge"? (I mean freeze like used in industry).
- Sara (age 22)
Morocco
A:

For these purposes we can think of jam as almost the same as sugar water.  If sugar water gets below what's called the "eutectic temperature" of sucrose-water solutions then only ice crystals and sugar crystals will be left after it reaches equilibrium.

Oddly, when I looked around to find that eutectic temperature I found some sources that said -9.5°C and others that said -14°C. I don't know what the accurate value is. 

Looking at specifications on industrial freezers, it seems they can get down to about -22°C. That should be cold enough to fully freeze the jam even allowing for some other solutes besides sugar. 

Mike W.


(published on 12/12/2013)

Follow-up on this answer.