Internet version [Naruhodo no Mori] Vol.44

by Yumiko Mori

---

Vol. 44     March, 15th, 1999

Supercooling

Home science experiments for mothers of elementary school children

Mom and Toshi are both in very excited state.
Water in the tube has become completely frozen within a second.
The water was in the 'supercooling state'.

Tae: "I was not watching. I missed the experiment."
Dad: "I wish you could have noticed us before you started."
Mom: "I didn't expect this experiment would succeed."
Toshi: "That was very exciting!"
Mom: "Yes, it was really exciting."
Toshi: "I put a piece of ice particle, and then suddenly, the water has started frozen near the ice particle. The freezing process spreads into the entire water, just like domino effects.
Mom: "It was quite pretty to see the freezing process spreading."
Tae: "I want to see it."
Toshi: "Shall we try again?"

Responding to the request, Toshi has decided to try the supercooling experiment again. The preparation takes a little bit time.

Toshi: "It perhaps ready. I am going to throw an ice particle into the water, OK?"
Tae: "OK!"
Dad: "I'm ready!"
Mom: "Go ahead!"

An ice particle was thrown in, and suddenly the water became frozen instantaneously.

Tae: "It's amazing! It's absolutely beautiful!"
Dad: "Amazing!"
Mom: "We did it again!"
Tae: "Show me! This is really frozen. It doesn't fall even I put upside down."
Toshi: "I'll try one more time."

Supercooling:  When you cool down water, the water becomes from liquid state (water) to solid state ( ice) at 0 Centigrade. However, if you cool pure water, it may not become frozen and remain as liquid even below 0 Centigrade. This state of the water is called supercooling.

Materials

Supercooling Experiment

1. Pour purified water into a glass cup until the water level reaches 3 cm from the bottom.

2. Place this glass cup in a bowl.
   Fill the bowl with ice, so that the glass cup is surrounded by ice.
   (Never put any ice piece into the glass cup.)
   The height of the ice pack in the bowl should be slightly higher than the water level.
   Leave some ice for later use. (Step #4)
   Sprinkle two tablespoonful of salt over the ice.

3. Measure the water temperature by sticking the thermometer into the water.

4. After 10-20 min later, when the temperature is down to -1 to -3 centigrade, take the glass cup out of the bowl very gently.
   If you see ice formation in the glass cup when you takes out it from the bowl, which is a sign of failure. When you don't see any ice, drop an ice piece into the glass cup.
   Watch very carefully what is going to happen to the water.

• You can make quick start if purified water is kept cold in the refrigerator.

• Don't put too much salt on ice even if the water temperature does not go down below 0 Centigrade quickly. If you do, the water may get frozen before you drop an ice piece.
  Be patient when you lower the temperature. Use a tall slim glass cup if available. The temperature should go down faster.

   This supercooling experiment was very exciting! Water turned into ice in front of our eyes. I wanted my children to experience this excitement. I wanted them to watch real experiments, not on the television. I am hoping, if any children find excitement in this experiment, he or she will like science. You can say the same thing for literature or music. I believe it is important that children become excited about something. When that happens, they should succeed in school.

---