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Chemistry Project Ideas: How to Cool a Beverage Quickly

January 1st, 2008

While searching for some easy physics or chemistry project ideas that my mother could use for teaching her classes, I remembered that several months ago, she had emailed me a video that was supposed to demonstrate how the second law of thermodynamics could be used for fast cooling of beverages. Fortunately, I had bookmarked it, so I returned to watch it again today.

Upon watching it for the second time, I noticed some things about the experiment that I had not really paid attention to before, and became especially intrigued by this little chemistry project idea after reading through the comments about the video at Metacafe.

The comments section contains several bits of ignorance posted by people who apparently did not understand the intent of the experiment or simply lack knowledge of the underlying scientific principles involved. I would like to address some of these issues here because there seems to be some genuine confusion and controversy about this.

1. Many people rated the video as “lame” or “dumb” and stated the obvious fact that a beverage (in this case a can of coke) could be cooled by simply pouring it into a glass with ice, as if this somehow invalidated the whole experiment. Apparently these simpletons do not have much experience with drinking soda, or perhaps they simply don’t care about taste. If one takes a warm soda (the one in the video was almost 80 degrees Fahrenheit) and simply pours it over ice, it will be significantly diluted by the melting ice and will also lose much of its carbonation. In other words, you will wind up with a flat, watery, and generally less desirable drink. The whole point of the experiment was to find a way to quickly cool down the beverage before pouring it over the ice. This method is supposed to work faster than simply placing the beverage in a refrigerator or freezer, which is normally what I would do to get the beverage cold enough for drinking at full strength.

2. Several commenters complained that the first few sips of coke would taste salty because the can had been dipped in salt water. The solution to this is fairly obvious- just rinse off the can with plain water before opening. Alternatively, it is also possible to use substances other than salt to dissolve in the water and lower the freezing point. I’m thinking about reproducing the experiment using sugar in place of the salt to see what kind of difference this might make in the temperature of the ice water and the total cooling time required to bring the beverage temperature down to an acceptable level. Meanwhile, it seems that some folks out there truly enjoy making negative comments on people’s posts without using their brains first.

3. There were a few viewers who disbelieved the experiment to some extent, claiming that the addition of salt to the water would make no difference in the cooling because “water cannot get below 32 degrees” or “the salt does not make the water colder”. They thought that the producer had “wasted” the salt and that using plain ice water would cool down the coke just as quickly.

I was a little unsure about this at first because I have never attempted this exact procedure before, but after further research, I found out that the salt does indeed lower the temperature of the water, even while it is still in the liquid state. After I thought about this some more, it realized that it makes sense. The whole idea behind putting salt on roads and sidewalks in the winter is to melt the ice and allow the liquid water to exist at a temperature somewhat below 32 so that it does not refreeze and create a safety hazard. There is a limit to this however; below temperatures of -21 degrees Celsius (-6 degrees Fahrenheit), even a completely saturated solution of salt water will freeze over.

Another source that explains this phenomenon fairly well is this page from worsleyschool.net about salt and the freezing point of water. It also includes some interesting recipes and information on how to use this knowledge to make various flavors of homemade ice cream.

4. Two of the commenters got confused about the temperatures and thought that the reading of 43 degrees meant that the beverage was still too warm and that the experiment didn’t really work. Eventually others mentioned that the temperatures were in Fahrenheit degrees instead of Celsius, which seemed pretty obvious to me considering the ambient conditions and the materials used. However, I noticed that the narrator in the video did not indicate which temperature scale was being used, so perhaps this should have been mentioned to avoid confusion.

5. A few people took a rather anti-capitalist bent and criticized the video as some sort of cheap money-making trick. They claimed that the producer had simply copied an easy high school chemistry experiment that was shown on a program called Mythbusters about two years ago.

Interestingly, it is true that the video is earning some money- Metacafe allows people to accumulate earnings of $5 per 1000 page views through its Producer Rewards program. However, there does not seem to be any problem here because the producer actually made his own video replicating the experiment and effectively granted Metacafe a non-exclusive license to display and promote the video according to their terms. Frankly, the idea that someone can make a one-minute video about an interesting experiment and earn over $3,400 from it is a good thing because it gives us hope that the freedom of the Internet can be used to alleviate poverty and promote prosperity for those of us who got left behind in the “real world” rat race.

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