This week we are channeling our inner “Elsa” and growing our own ice!
For today’s experiment, you will need the following household materials:
- Room temperature bottled waters in a plastic bottles, freeze as many bottles as you want! (distilled or purified works best; do NOT use a glass bottle)
- Food coloring (optional)
- Wide-mouth cups
- Ice cubes
- Tray with sides (like a baking sheet) or large shallow dish
If you choose to add one or two (2) drops of food coloring to your water, now is the time to do so.
The preparation for this experiment will take a little longer than some of our recent experiments. Begin by placing the water bottles in the freezer on their sides for approximately 2 hours and 45 minutes (depending on your freezer – it may take more or less time). The purpose of putting the bottles in the freezer is to get the water to an extremely cold temperature, which makes the ice formation possible.
If your bottles start to freeze, just take them out, let them return to room temperature and start again and keep them in the freezer for 15 minutes less.
If ice doesn’t start to grow when you begin pouring your water over the ice in the cup, your water is not cold enough, and you will need to return the bottles to the freezer for another 15 minutes or so. We did have to try our experiment a few times to get the water to just the right temperature.
When your water has been sitting long enough, and is free of any ice, carefully remove it from the freezer. Be careful not to bump, bang, or drop the water bottle or the whole bottle may freeze into a solid block of ice instantly! Place a couple of ice cubes into a wide-mouth cup, like the one pictured here.
Begin slowly and carefully pouring the cold water over the ice.
Notice anything different about your seemingly average cup of ice? You should notice a mound of slushy ice forming on top of the ice cubes in your cup!
So what’s the science?
Ice crystals, like snow, need to stick to something to start forming. This is called nucleation. The purified water in the bottles does not have any impurities to start the nucleation process. This is why the water in the bottle is actually below freezing, or, supercooled. If you drop or bang the water bottle, the nucleation process will jumpstart and all of your water will snap freeze. Pouring the supercooled water onto the ice cubes gives the water something to cling onto and form ice crystals. As water freezes, it releases any latent heat (heat energy required for a phase change to occur, such as an element going from a solid to a liquid, or vice versa) into the ice causing the temperature to warm up just above freezing. This leaves you with the slushy consistency that you noticed at the end of the experiment, making it perfect to build ice towers!
As always, it is important to note that an experiment uses a variable (something that changes) to answer a question. To turn this demonstration into an experiment, you have to change something! Check out these ideas to get you started:
- If placed in the freezer at the same time, do different types (brands) of bottled water form a different slush consistency?
- How does food coloring impact the slush compared to just plain purified bottled water?
Try it and let us know how your experiment turned out on our Facebook, Instagram, or Twitter page using the hashtag #gscscience!