Restaurant Fun From The Science Department

For some family fun while you wait for your food I offer the following demonstration:

Set the Stage:

1. Place an ice cube from your drink on the table.

2. Offer the following challenge to your loved ones: “Can you pick up this ice cube with only this string (cotton works best)?”

3. Watch with glee as they struggle.

The Solution:

1. Soak the string in your water glass.

2. Lay the wet string across the top of the ice cube.

3. Poor salt liberally over the top of the ice cube covering the string completely.

4. Wait 20-30 seconds.

5. Lift the ice cube by pulling up on both ends of the string.

6. Be sure to ask the following question: “What’s happening here?”

The Learning:

Salt and many other compounds have the ability to lower the freezing point of water. This is called Freezing Point Depression. We add salt to road ways, anti freeze to cars, and rock salt to ice cream makers all to lower the freezing point of water. The water in the string actually freezes to the ice cube because you have lowered the temperature of the now salty, water slush, on the top of the cube.

~Dean Whitfield
Math and Science Department Chair