Science Buddies: "Ask an Expert"

My science fair project is "Which liquids freeze faster?"

I froze liquids like vinegar, milk, coke, juice, lemon juice, salt water, sugar water, bottled spring water, distilled water and sparkling flavored water to see which one froze faster. I predicted the distilled water would freeze fastest because it has no added ingredients but in my first two trials the carbonated sparkling water froze first. I made sure I used the same amount of each liquid and that they were all at room temperature to start.

I can't seem to find any reason for this to happen. Higher pressure makes liquid freeze at a lower temperature so is the carbonated water at a lower pressure because of the bubbles? Or could the carbon dioxide bubbles cool faster then the liquid and help cool the liquid faster?

Thanks for the help.

Mushbrain wrote:My science fair project is "Which liquids freeze faster?"

I froze liquids like vinegar, milk, coke, juice, lemon juice, salt water, sugar water, bottled spring water, distilled water and sparkling flavored water to see which one froze faster. I predicted the distilled water would freeze fastest because it has no added ingredients but in my first two trials the carbonated sparkling water froze first. I made sure I used the same amount of each liquid and that they were all at room temperature to start.

I can't seem to find any reason for this to happen. Higher pressure makes liquid freeze at a lower temperature so is the carbonated water at a lower pressure because of the bubbles? Or could the carbon dioxide bubbles cool faster then the liquid and help cool the liquid faster?

Thanks for the help.

Very interesting result. See if there is a scientific principal at play, or if it is some small error in your method that makes just enough difference. Try a google search for freezing point and look at freezing point depression. I found these two sites of interest.

http://mattson.creighton.edu/SodaWater/SodaWater.html
http://members.aol.com/profchm/fpdepres.html

How are you testing the time it takes to freeze? Are you sure that your measuring method is not affecting the time it takes? What was the difference in time?

Could the way that you pour the water into the container for freezing make a difference?

Do you know how much carbonate is dissolved in the sparkling water?

25 ml of each liquid was poured through a funnel into a ice cube tray slot. In the first trial I began checking every 30 minutes but since they were freezing faster than I thought they would I began checking every 15 minutes. The Sparkling water froze at 90 minutes and the distilled water was 105 minutes. In the second trial it was 80 minutes and 90 minutes for each. For the second trial I started my intervals at 20 minutes and went down to 10 minutes. The freezer temperature was -18 C.

The sparkling water was poured straight from the container since it was already at room temperature. Should I let it sit open for a while before I freeze it to let it get flat? I'm not sure I should change anything since I'm suppose to do the same experiment 3 times.

I would recommend checking every 15 minutes initially, but then narrowing down your check time to every minute just to make sure about the large difference that could occur due to the increment used.

rc1974 wrote:I would recommend checking every 15 minutes initially, but then narrowing down your check time to every minute just to make sure about the large difference that could occur due to the increment used.

One other effect you might look at that could make the difference. Are there parts of the freezer that are colder than others? You can check with thermometers, or by placing trays of the same type of liquid in different spots in the freezer. If there are colder zones, you can probably modify your method a little to ensure this affect is equal on all the trays.

Now that you know the aproximate time to freeze, checking more often as you get closer to freezing as advised above will help you measure smaller differences in the time required.

Continue pouring the sparkling water warm and directly into the ice sube trays just as you have been. I would not let it go flat first. All of the liquids to should start at the same temperature before going in the freezer. This will also keep the most carbonation in the liquid so you see the greatest effect of the carbonation.

Sounds like good advice, Kraig.

Mushbrain, a couple other random thoughts you might want to consider:

- If the effect you've observed is repeatable, is it due to the soda water freezing at a higher temperature, or reaching the same temperature faster?

- If it's the later, you might want to think about the role heat transfer plays in this. Is the faster sample better able to exchange heat with the air or the walls of the freezer and therefore cooling faster? Or, counter-intuitively, is the faster sample such a poor thermal conductor that the top surface is gets cold while most of the liquid inside is still warm?

- Is there anything else about the soda water that's different? (Sodium, for example?) You could rule that out by letting a sample go totally flat (overnight perhaps) and comparing that.

- If you stagger the samples in an ice tray (normal / sparkling / normal / sparkling / etc), it might give you a really easy way to see if location in the freezer is important.

Good luck,
Erik

EDS wrote: - If the effect you've observed is repeatable, is it due to the soda water freezing at a higher temperature, or reaching the same temperature faster?

That's a really good question. Thanks! I think it is cooling faster but I think I need to put all the possabilities in the conclusion section of my project.

I was thinking of letting it go completely flat then doing the experiment again with just sparkling water and distilled to see what happens and adding that to my conclusion too. This is the first time I have done a science project so I'm still figuring out how to format it.

p.s. The Sparkling water is sodium free and sugar free.

Mushbrain wrote: p.s. The Sparkling water is sodium free and sugar free.

and is calorie free. (and safe from the possible carcinogenic effects of diet soda) - (this is a non-Science Buddies comment, please excuse)

I was curious and did the experiment with just distilled water and carbonated sparkling water that I let go flat over night. The carbonated water still froze faster even though I didn't think it would.

Could it have something to do with the extra oxygen molecules in the carbonation? Isn't carbonation Carbon dioxide (CO2) ?

Mushbrain wrote:I was curious and did the experiment with just distilled water and carbonated sparkling water that I let go flat over night. The carbonated water still froze faster even though I didn't think it would.

Could it have something to do with the extra oxygen molecules in the carbonation? Isn't carbonation Carbon dioxide (CO2) ?

The web page http://www.madsci.org/posts/archives/ma ... .Ch.r.html may help. I haven't worked things out, but the page does seem to cover solutions in general.

Mushbrain wrote:I was curious and did the experiment with just distilled water and carbonated sparkling water that I let go flat over night. The carbonated water still froze faster even though I didn't think it would.

Could it have something to do with the extra oxygen molecules in the carbonation? Isn't carbonation Carbon dioxide (CO2) ?

Yes, carbonation is CO2. But when the carbon dioxide is put into water, some of it reacts with the water... H2O + CO2 = H2CO3. The resulting water is slightly carbonated (CO3--) and slightly acidic 2(H+). Even when the water is no longer emitting visible carbon dioxide bubbles, there will still be some CO2 in solution.

Things are actually even more complicated than this, as some CO2 will be in solution, whether or not it chemically mixes with water. When the soda water stops fizzing, all that means is that you now have a saturated solution of CO2, instead of a supersaturated one. But there won't be much CO2 actually left behind; most liquids don't hold on to much of neutral gases.