Enough about climate change and CO2 flux! (for today anyway). I had been talking with my students at school before I left and collected some great ideas about experiments we could conduct while in Alaska. One of the questions to test was; at what temperature can boiling water change into snow? With the morning temps holding around -25 F lately, Elizabeth and I decided that this may be a good time to run some experiments.
The experiment begins with a pot of boiling water. This water is ready to change from a liquid to a gas.
We had to check for the official temperature of the experiment.
We had checked the temperature, and at around 9:00 am we noted it to be 18 degrees F below zero. This seemed like a good place to start testing, so we grabbed the pot of boiling water off the stovetop and hurried outside to see if it would change. It did! There were some larger drops of water that spilled out onto the ground as liquid, but the major part of the water went into the air a changed instantly into a small cloud of power snow. We repeated the experiment several times, as all good scientists do, and observed the same results each time.
As Elizabeth flung the water into the air we could see the liquid change to a solid white puff of crystals. It looked really cool!
Why does this happen? There are many factors that come into play here so I’m not sure that I will cover all of them, but here are the more important ones I can think of.
First the temperature of the air is the largest factor. The colder the air, the faster the heat will transfer from the water. We have started at -18 F.
Then the size of the water droplets is a factor. The smaller the water pieces the more surface area they have and the faster the heat will be lost to the air, causing faster freezing of the water. With this in mind, the higher you throw the water into the air, the better.
Next the temperature of the water comes into play. The hotter the water, the faster the droplets want to evaporate. This not only helps the water break into even smaller pieces, but also the evaporation process has a cooling effect on the droplet that helps it cool down even faster.
Also the purity of the water helps this change happen. The tiny parts of salts and minerals in the water give the ice a place to start forming when the temperature is low enough. The impurities in the water act as little seeds that begin the formation of ice crystals.
The new snow hung in the air for a few seconds before slowly drifting down to the ground.
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All of this is the process that ski resorts use with their snow guns to make manmade snow for the slopes. It is simple and works well. So we have our first data point. We will try and test other temperatures as we have time. It was really cool to watch the whole thing happen! Having fun with science is the name of the game!