 |
 |
 |
 |
This science project is courtesy of Tech TV's (www.techtev.com) Jeremy Edy, who demonstrated the Candle Spinner on the July 10, 2001, episode of "The Screen Savers." The project demonstrates the conversion of potential energy to kinetic energy using empty film canisters and birthday candles.
- Plywood scrap, approx. 8x8 inches
- Wood dowel, 1/4-inch diameter
- Sewing Needle
- Four Popsicle sticks, plus extras as needed
- Two film canisters, plus extras as needed
- Hot glue gun, or other glue source
- Modeling clay
- One pack of 24 birthday candles
- Scissors
- Cigarette lighter or matches (Ask an adult for help. Do not use a lighter or matches on your own!)
Drill a hole in the center of the plywood scrap so that the dowel will fit snugly and stand upright.
Drill a small hole vertically into the top end of the dowel 3/4-inch deep.
Set the needle standing upright into this hole.
To make the propeller, glue four Popsicle sticks at their centers to make an eight-pointed star.
Cut each of the two film canisters into four pieces by making vertical cuts in the curved canister wall every 90 degrees. Complete the cuts along the bottom of each canister, leaving a pie-shaped wedge of plastic (on the bottom of the canister) attached to each curved segment.
Cut the small plastic lip (where the top of the canister normally fits) off of each canister piece.
Glue one canister piece to each of the eight points of your Popsicle star. Each canister piece should overlap with about one inch of the Popsicle stick, with the edge of the curved canister wall flush with the edge of the Popsicle stick. Make sure each canister piece is oriented in the same direction, and that the pie-shaped wedges are all facing outward.
Using a countersink drill bit if you have one (or the head of a large nail, if you don't), make an indentation on the undersurface of your propeller where all the Popsicle sticks intersect.
Balance the propeller on the needle of the stand so that the indentation in the Popsicle stick rests on the needle point. Press small balls of modeling clay onto the pie-wedge points of each canister piece until the propeller balances on the needle without assistance.
Roll the remaining modeling clay into a long, thin cylinder about one inch in diameter and about 15 inches long.
Curve this piece of clay into a ring around the base of the dowel. Note: You may need to experiment with the length of the dowel. Try different heights of the spinner above the candle flames.
Press the birthday candles vertically into the ring of modeling clay. Start with four or six candles and increase the number until the spinner is moving. Too many candles may make too much heat and start melting the plastic canisters.
Light the candles, and watch the propeller spin!
How Does the Candle Spinner Work?
Like all other substances around us, candles are made of molecules. The molecules that make up the wax in candles are large and store a lot of energy in the bonds between their atoms. When you light a candle, oxygen from the air is combined with the wax in the presence of heat, and these large molecules are broken down into smaller ones, mostly water vapor and carbon dioxide gas.
The energy that was stored in the bonds of the wax molecules is released in the form of light and heat. This heat energy causes the molecules in the air above the candles to move faster.
As the molecules speed up, they bump against each other with greater force and spread out, causing this heated air to be less dense than the cooler air outside the candle ring. The cooler, denser air pushes on the hot, low-density air, causing it to rise up through the propeller. This rising air strikes the blades of the propeller, which, due to their shape, shunt the air off to one side and are in turn pushed the opposite direction by the air. Because the needle point generates almost zero friction with the Popsicle stick, the propeller starts to rotate, and some of the potential energy stored in wax molecules is converted to the rotational motion of the propeller.
This spinner is similar to the Advent "angel carousels" seen during Christmas time. You may also want to substitute a plastic pin wheel, just don't get too close to the candle flame.
