Don't just toss out that empty Coca-Cola can when you're done with it. There is a wonderful craft project that can be done using that can: the Coke can boat. You can actually make a functioning, self-propelled, steam-powered toy boat using an aluminium soda can. It is a simple and educational project, great for children in middle and high school, that demonstrates the Newtonian Laws of thermodynamics.
Bend the copper tubing around the large pen so that a coil is formed with two equal lengths of tubing extending from it.
Use the craft knife to carefully cut the aluminium can in half lengthwise. You only need one of the halves.
Glue the small votive candle or tealight to the inside of the can half about one inch from the top end of the can.
Bend the ends of the coiled copper tubing downward so that they will be submerged when placed in water.
Poke two holes into the bottom end of the can. The holes should be the same distance apart as the ends of the copper tubes.
Insert the ends of the copper coil through the holes in the can and allow them to extend far enough so that the actual coil is directly over the wick of the candle. Use tape to hold the coiled tube in place.
Fill a bathtub with six inches of water.
Fill the copper tubing carefully with water. This can be done by turning on the faucet to a drizzle and placing one end of tubing under the water and filling both tubes and coil entirely with water. Carefully, place the boat in the water and make sure the tubes are submerged. Some will spill out, but as long as water is in the tube, the experiment should work.
Light the candle with the boat resting in the water and facing forward. When the water in the coil is heated to boiling, the soda can boat will begin to move forward.
The boat can be decorated however you wish. You may add a sail, a paper mast or whatever your imagination can produce. The boat moves because steam is produced in the coil, which forces water out of the tube. The steam then cools and condenses, drawing more water into the tube to become steam. These reactions balance out and push the boat forward.