Homemade Heat Detector

Here's how to make a homemade heat detector:
Materials:
.Rubber band
.Wooden block of wood. The wood block should be large enough for the rubber band to fit tightly around, but small enough not to snap the band.
.Large pin or thin nail
.Poster board or cardboard
.Scissors
.Matches or other direct heat source.

Procedure:
1. Cut the shape of an arrow from your poster board or cardboard. The arrow should be about the length of your wood block.
2. Take your rubber band and stretch it around the outer edge of your wooden block so it's snug.
3. Push your pin through your arrow at the center of the arrow base (the side opposite the arrow triangle).
4. Carefully place the pin under the rubber band, centered along one of the edges of the block.
5. Light a match and carefully bring it close to the rubber band, closest to the pin.
6. The cardboard arrow will begin to rotate slowly anti-clockwise.
7. Place the match on the opposite side of the pin.
8. The cardboard arrow will begin to rotate clockwise.