1. Metal tube (a cigar tube works great -- ask an adult to get you one)
  2. Two pieces of strong, stiff wire (like clothes hanger wire) about 18-inches long
  3. Cork that fits snuggly into the end of the tube
  4. Two food warmer candles (in metal cups)
  5. Balsa wood (4 inch by 8 inch, 1/2-inch thick)
  6. Masking tape
  7. Hammer and three nails
  8. Matches
You'll need an adult's help with the matches and the hammer and nails!

Put the cork into the end of the metal tube making sure its very tight. Carefully poke a hole through the cork with a nail.
Take the two 18-inch lengths of wire. Wrap the wire around metal tube about one-inch from each end of the tube, and twist the wire tightly with the pliers so the tube is firmly held by the wire and won't slide.
Cut a boat shape out of the balsa wood, making a triangle bow at one end. Hammer two large nails in each end about one inch in from each end. The nails will help to stabilize.

Mount the two candles about 1-1/2 inches from each end of the wood. Use loops of masking tape to stick the metal cups to the wood.
Take the tube with the wire and mount the tube so the wire will hold the tube just above the candles. Wrap the ends of the wire around and under the board and twist the ends neatly on the underside. (See picture.)

Carefully remove the cork from the tube and fill the tube about three-quarters full with very hot water. Tightly replace the cork. Make sure water will drip out the hole in the tube.
Fill up a bath tub or a large sink with water.
Put your boat in the water and ask an adult to carefully light the candles.

 

The heat of the candle will cause the water in the tube to boil. The water will change to steam and the steam will escape out the hole in the cork pushing the boat forward in the water.

Here are some questions to think about:

  1. Why use hot water in the tube?
  2. What would happen if you used cold water?
  3. What would happen if you didn't put a hole in the cork (DON'T TRY THIS!)?
  4. What would happen if the hole in the cork were larger?

What's Happening

There are two different things to learn here.

A rocket works the same way. Hot gases and fire come out of the motor of a rocket. The gases coming out the nozzle at the bottom of the rocket come out in one direction. These escaping gases push the rocket in the opposite direction.

Second, energy from the candles changes the water into a gas (water vapor or steam). The steam can escape. Steam is used in a lot of energy power plants.


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