Boiling Ice
What You Need • Adult helper • Glass test tube • Crushed ice • Steel wool (can be purchased at the grocery or hardware store) • Water • Metal tongs or test tube holder • Candle lighter
1 Begin by filling the test tube about onethird full with crushed ice. Pull out a small amount of steel wool from the pad and put it on top of the ice. Press it firmly into the tube. Fill the test tube with cold water
2 Have an adult light the candle lighter and, with the tongs, hold the middle portion of the test tube over the flame.
If the ice was allowed to float in the water and then the water was heated, the ice would melt due to Q convection. This means that as the water warms it would rise because it’s less dense and it would melt the y water at the top. In this trick, however, the ice is held at the bottom of the test tube by the steel wool. The cold water in the top of the test tube warms when heated— and even boils—and becomes less dense. But it’s already on top and doesn’t circulate to the bottom.
Pinky Power
What You Need • Volunteer • Chair
What You Do Gather an audience and tell them that you will demonstrate the previously unrevealed power of a pinky. Ask a volunteer to sit all the way back in the chair with his hands in his lap. Point and place your pinky finger in the center of his forehead. Ask him to stand up without using his hands or arms to help. He can’t do it! How It Works The center of gravity, also known as the center of mass, is a point where most of the object’s mass is concentrated. For humans, if your center of mass is not over your base of support (like a chair or your feet) you will lose your balance. You can find the center of mass of any object by balancing it on your finger (assuming it’s not a refrigerator!). The point where it balances is its center of mass. In this trick, in order to stand from a seated position you must lean forward to move your center of mass over your feet (the base of support). If a pinky is there to prevent that shift, you can’t stand up.
Balloon Kebabs
Balloon Kebabs
You will need:
Several latex balloons • Bamboo skewers (available at grocery stores) • Cooking oil
Whit You Bo IBlow up the balloon about three-quarters full, so that there is still some room for air. Tie it off with a knot Dip the sharp end of a bamboo skewer into some cooking oil. 2 Assemble an audience. Tell them you can put the skewer through the balloon without popping it. Find a spot near the knot of the inflated balloon where the latex is thicker and darker than the rest of the balloon. Using the sharp end of the skewer, gently twist it around and around while pushing it through the balloon. Once the skewer is in the balloon on A one side, twist and push the skewer through the opposite side of the balloon (near the top). It will come out the other side without popping the balloon. Note: The balloon will slowly deflate as the air leaks out, but this can take a while. See how many skewers you can put through one balloon! How It Works Balloons are made of thin sheets of rubber latex. Latex is made up of molecules called polymers, which are in large strands. These strands of molecules are stretchy, which is why you can blow up a balloon. When you don’t blow it up fully, some of the polymer strands are not stretched to their maximum at places, like at the knot or top of the balloon. So, when you puncture the balloon with the skewer at those spots, the polymer strands can stretch around the skewer without popping the balloon.
