Tuesday, September 24, 2013

What's Cooler Than Being Cool?

by student blogger Kristin

Super Chilled Water Experiment  

All throughout this semester, I have not had Culinary Science lab classes on Thursdays. This means every Thursday afternoon I am off and free to do whatever I want. What do I do with this free time you may ask? Well, more science of course!
Today my partner Jovany and I conducted an extracurricular experiment on super chilling both water and soda. We have both seen videos and done research on the topic but wanted to make it happen ourselves. Basically, super chilling is the phenomenon of bringing water below freezing temperatures without turning to ice. When a bottle of liquid is left unopened in the freezer for a long time undisturbed, the substance will remain liquid. Take it out of the freezer and add any type of nucleation site, however, and the liquid will turn to ice.

********CAUTION: SCIENCE AHEAD********
Water’s ability to form ice is directly related to the concept of hydrogen bonding. This is the bond shared between two molecules of water at any given time. When water molecules are moving faster, the molecules are able to slip past each other and remain in the liquid phase. When temperatures drop, water molecules begin to move more slowly. The lack of speed allows each water molecule to bond with potentially four other water molecules in a rigid crystalline structure. This structure of water is more commonly known as ice.

Photo courtesy of Wikipedia.com

Water molecules will not form crystals solely based on low temperatures however. The formation of the crystalline structure is dependent upon the existence of a nucleation site. The nucleation site could be anything from a small impurity in the container to a gas bubble suspended in the water. As slower moving water molecules interact with this site, they begin to form ice crystals. These crystals get in the way of and bond with other water molecules and the phase change from liquid to solid has begun. The water molecules arrange themselves in a crystalline pattern forming a solid that is actually less dense than liquid water.

Think of this phenomenon as an oyster and pearl. When undisturbed, an oyster will go on living its life without producing pearls. Add a grain of sand to the pearl, however, and everything changes. The sand agitates the oyster which then begins forming a barrier around the foreign object. This barrier grows larger over time until the pearl is formed. The seemingly small impurity of a grain of sand is responsible for the total formation of the pearl.
When a liquid is contained within its original bottle, there are no nucleation sites for the ice crystals to start forming. The plastic of the bottle is too smooth and without being agitated, the slowing water molecules will have a hard time crystallizing. Therefore when everything falls into place, water can dip below its freezing point without turning into ice. Once you take this water out of the freezer and agitate it, the water molecules will not be able to avoid each other and will almost instantly form into ice crystals. This property of water can be manipulated many ways to help depict the concept of super chilling. 

This process is easier said than done, however; A concept that my partner and I experienced on this first attempt for our super chilling liquid experiment.
Prep: Water and Soda into Freezer
In order to properly conduct this experiment, it is first necessary to allow the liquid to sit in the freezer for a few hours. This gives the liquid time to reach below freezing temperatures. My partner placed five bottles of both water and soda into the freezer in the morning about 2 or 3 hours before we intended on conducting the experiment that afternoon.

Experiment # 1: Pouring Water
One way to present the idea of super chilling is to pour super chilled water into a glass. As the water molecules hit the bottom of the glass, they will start aligning themselves in the crystalline structure and instantly turn to ice. The water will actually continue to stack higher on itself, leaving you with a tower of instant ice. When done correctly, this is a mind blowing visual.

Since this was our first time running this experiment, we did not achieve quite the same ground breaking results. However, we did see some change in our water! As we poured the water out into a beaker, the water hitting the container remained liquid but the liquid inside the bottle became icy and slushy. Every time we tried to replicate the experiment we got this same result. After discussing the unforeseen result with my partner, we decided that the speed at which I was pouring was too fast, creating turbulence within the bottle and therefore ice crystals.

Next time, we decided we will try pouring slower and onto some sort of nucleation site such as an already formed ice crystal.

Experiment #2: Smashing Water
Another more reliable way to show the properties of super chilled water is by simply taking an unopened bottle out of the freezer and instantly hitting it against a hard surface. Because the water molecules cannot escape each other, they will form hydrogen bonds with one another and instantly start forming ice crystals. This is my personal favorite because you can watch the ice “crawl” from one end of the bottle to the other! It is also a very cool party trick!

Because pouring out the water was not quite working, this was our next step. My partner and I took out a bottle of water from the freezer and as he recorded it, I smashed the bottle down on the table. Within seconds, we could see ice forming from the top of the bottle quickly growing down towards the bottom. Shortly, the bottle was filled with ice and we had run our first successful super chilling water experiment!

While we are working on getting better footage and results in the future, here is the video of this first bit of success!  http://instagram.com/p/edats2SyBB/

Experiment #3: Pouring Soda
While we were designing the experiment for super chilled water, Jovany found a video on super chilling soda. The experiments were all pretty much the same as the water, but the color difference created a really cool visual. We were especially interested in the effect the carbon dioxide dissolved in the soda solution would have on the experiment. So, we of course decided to try it!

We had high hopes for this experiment but the results were not too far off from that of pouring water. As we poured the liquid out of the bottle, the agitation from pouring and the additional turbulence caused by the carbon dioxide caused the soda to become slushy. The liquid hitting the bottom of the beaker experienced a bit more change than the water however. As the soda hit the bottom of the glass, it changed to slush and formed a slushy raft on top of the soda.

After somewhat failing at this experiment, we did some more research and discovered some more reliable ways to conduct the super chilling experiment with soda. I am excited to see the outcomes of these future experiments!

Experiment #4: Smashing Soda
Although this experiment was conducted the same way as the smashing water, the results were much different. Instead of forming a single block of ice like the water bottle did, the soda formed small ice pieces that caused the bottle to look like a slushy. The Carbon Dioxide bubbles coming out of solution helped to form ice crystals in the soda but also could have formed barriers to keep these bits of ice crystals from reacting with one another. The good news is that it still looked awesome and science still happened!

Now that my partner and I have some better ideas on how to properly manipulate super chilled water, we are working on perfecting this experiment to get the correct results. I will keep you posted on any of our findings!

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