If you've ever been on a tropical vacation with your child, you may have gone underwater in a special kind of submarine that allows the people riding inside to see fabulous sea creatures—all kinds of bright and unusual-looking fish and plants and other things—without getting wet. If your child hasn't taken a ride in a submarine, he's probably read about one, or seen one on television, or learned about submarines in a class or on the Internet. But how does a submarine actually work? Here's a fun way to figure it out.
What You Do:
- Use the hot-glue gun to melt three holes approximately 1 inch (2.5 cm) apart along one side of the plastic bottle. Use the glue gun to melt a hole in the center of the cap of the bottle just big enough for the tubing to fit through.
- Place each fishing weight lengthwise next to one of the holes, and use a small piece of the tape to attach the weights to the bottle.
- Thread one end of the plastic tubing through the hole in the cap so that approximately 2 inches (5 cm) of the tubing extends inside the bottle. Then, making sure that the tubing stays in the position you've just put it in, use a little bit of modeling clay to seal the area between the cap an the tubing. This is your “submarine.”
- Put your submarine into the bathwater. Push the submarine to the bottom of the tub so that its fills completely with water.
- Blow through the plastic tubing and watch what happens to the sub.
When you pushed the bottle under the water, it filled up with water and sank to the bottom. The side of the bottle with the holes and fishing weights was heavier, so this side faced down toward the bottom of the tub. As you blew into the plastic tubing, the air from your breath began to fill up the bottle. When enough air was inside the bottle to make it float, it began to move upward in the tub. Finally, air began to come out of the holes on the bottom side of the bottle, and bubbles started to rise.
Reprinted with permission from "Bathtub Science," a book that provides hours of water play ideas and experiments, and teaches science at the same time. By Shar Levine and Leslie Johnstone (Sterling Publishing Co., 2000).