Kids, here’s a way to cool off and amaze your friends by making a soda turn into a slushy on command. And all you need is some soda and a freezer! The slushy project works especially well with 16-oz or 20-oz carbonated soft drinks in plastic bottles.
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
Procedure
- Start with a room temperature bottle of soda pop. You could use any temperature, but it's easy to estimate how long it will take to supercool the liquid if you know your approximate starting temperature.
- Shake up the bottle and place it in a freezer. Do not disturb the soda while it is chilling or else it will simply freeze.
- After about 3-1/2 hours, carefully remove the bottle from the freezer. Each freezer is a little different, so you may need to adjust the time for your conditions.
- There are several different ways to start the freezing of the supercooled liquid. (a) Open the cap to release pressure, reseal the bottle, and turn the soda upside down, causing it to freeze in the bottle. (b) Slowly open the bottle, releasing pressure slowly, and pour the soda into a container, causing it to freeze into slush while you pour. You may pour the drink onto an ice cube to get it to freeze from the ice cube back toward the bottle. (c) Slowly pour the soda into a clean cup, keeping it liquid. Drop a piece of ice into the cup to initiate freezing. Here you can watch the crystals form outward from the ice cube.
How It Works Supercooling a liquid means to chill it below its normal freezing point without turning it into a solid. Although sodas contain ingredients besides water, they are dissolved in the water and so they don't provide nucleation points for crystallization to occur. The added ingredients do lower the freezing point of water (freezing point depression), so you need a freezer that gets well below 0°C or 32°F. You shake up the can of soda pop before freezing it in order to eliminate any large bubbles that could act as sites for ice formation.
Notes You can make instant slush in cans, too, but you can't see what is going on inside the can and the opening is smaller and harder to open without jarring the liquid.
If you don't have access to a freezer, you can use a large container of ice. Sprinkle a large quantity of salt on the ice to help make it extra-cold. Cover the bottle with the ice. The salt-ice mixture creates an example of freezing point depression.
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
September 2013
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References:
Anne Marie Helmenstine at chemistry.about.com:
http://chemistry.about.com/od/ediblescienceprojects/a/Instant-Slushy-How-to.htm?nl=1
