Here’s a magic trick you can do to amaze your friends! You can lift an ice cube without tying any knots! Unlike most magic tricks, which use illusions, this one uses science.
Magic Trick Materials
String
Ice cube
Salt (in a shaker works best)
1) Put the ice cube on a plate. Put a little bit of water on top of it.
2) Cut a piece of string (about 6 inches long). Put one end of the string in the water on the ice cube. Show everyone that the string is not attached to the ice cube.
3) Sprinkle a little salt on top of the ice cube. If you want to be mysterious, you can tell everyone that it is magic powder. If you want to be scientific, you can explain that the salt will melt a little bit of the ice so the string sinks into the cube. Then the coldness of the cube will refreeze the water around the string.
4) Wait a minute or so (it’s a good idea to practice this beforehand, so you know how long it will take). You will probably be able to see the string sink into the ice a little bit.
5) Once you feel confident the string is in the cube, pick it up and amaze your friends!
Why does this work? (And another experiment to try)
Almost everyone knows that water freezes (or melts) at 32oF (0oC). That’s a physical constant, which means that under normal conditions, water always freezes or melts at this temperature. But, we can do something to change the melting point of water. In the winter ice forms on roads and sidewalks, making travel slippery and dangerous. When the temperature is below 32oF (0oC), ice will not melt by itself. To make it melt, people put salt on the ice. Adding salt to the ice lowers the freezing point of the ice (now an ice-salt mixture).
You can see this for yourself, with this easy experiment.
Materials for observing the change in freezing point:
Insulated cup (Styrofoam or double walled travel mug—a regular cup will work, just not as well)
Water
Ice
Salt
Thermometer (Be sure you have one that can read temperatures below freezing!)
1) Fill your glass, about 2/3 full, with ice. Add cold water, leaving some room at the top (so you can stir the solution).
2) Wait a few minutes (keep stirring gently) and then measure the temperature. It should be 32oF(0oC). If it is not, you may need to either wait a little longer or add more ice.
3) Add salt to the ice/water solution. You will need to add a lot (1/4 to 1/2 cup, or more, depending on the size of your cup). You want the solution to be very salty.
4) Wait a few minutes and measure the temperature again. How low did it go?
5) If the temperature of the solution only went down a few degrees, add more salt and measure again!
