Instant Ice from Supercooled Water Demo
Materials
Salt (table or rock) Large Beaker (1000 ml) or small insulated
cooler
Ice stirrer
Thermometer Clean unused test tube
Distilled water
Fill a large beaker with ice. If the cubes are large it helps to break them up into smaller pieces to do the demonstration. Add about _ to _ cup of salt directly to the ice. DO NOT ADD WATER. Stir the ice and salt mixture thoroughly. Check the temperature of the ice. The temperature should drop well below 0o C (32o F). This will require a few minutes of stirring.
Fill the clean, unused test tube 2/3 full with distilled water. It is important that the water is distilled, but it is more important that the test tube be perfectly clean. Any irregularities, scratches, or foreign particles on the inside of the test tube will cause problems for this demonstration.
When the temperature is about 10o C (about 4o F), your ice slurry should be ready.
Step 1. Place the test tube into the ice slurry. Allow the water to freeze. You should notice that the ice is hard and has many small air bubbles. Warm up the test tube with your hand or with warm water. This will cause the ice to melt. You will notice the bubbles in the ice will cause any liquid water in the test tube to bubble or fizz like week soda. This should happen and indicates that you are well on your way to having a good demo. Stir the slurry to maintain the low temperature.
Step 2. After the ice has completely thawed, place the test tube back in the slurry. Avoid any movement of the test tube. Look down into the distilled water and observe the freezing. Just as crystals form on the outside, pull the test tube out of the slurry. As you remove the test tube it should freeze. The crystals should be long and thin, and radiate toward the center of the test tube. Hold the test tube in your hand to heat it up. These ice crystals are very fragile and the ice should melt very quickly. You may have to repeat this step two or three times. During this stage you are making sure any gas molecules are removed from the water. Stir the slurry to maintain the low temperature.
Step 3. Return the test tube to the ice bath and measure the length of time it takes for the ice crystals to begin forming. This usually takes a minute or two for the freezing to occur. Thaw the ice with your hand to melt the ice.
Step 4.
Chip a small piece of ice to serve as a seed crystal. Place the
test tube in the slurry. Allow the test tube to cool in the slurry
for 10 seconds less than it takes for it to starts to freeze.
Slowly and carefully remove the test tube from the slurry. Drop
the seed crystal in the water. It should freeze instantly with
long thin ice crystals.