Conduction
Conduction is a term used to describe the flow of heat through an object. Objects that are good at conducting heat are called thermal conductors. Metals are thermal conductors, but plastics, fur, wool, and gases are usually poor thermal conductors. Poor thermal conductors are called thermal insulators.
The Dropping Pins Experiment
Aim: To observe conduction along a metal rod.
Equipment: A metal rod, retort stand and clamp, Bunsen burner, petroleum jelly, 4 drawing pins, stop watch
Method:
1. Set up and light a Bunsen burner
2. Smear a small amount of petroleum jelly on to the head of each drawing pin
3. Attach the drawing pins at even intervals along the length of the metal rod
4. Clamp one end of the metal rod to a retort stand
5. Position the retort stand so the unclamped end of the metal rod is in the Bunsen burner flame and start the stop watch
6. Record the time it takes for each pin to drop in the table below.
Discussion: As we did the experiment, we saw that the pins drop quickly as we opened the Bunsen burner.
Explanation: When particles at one end of a metal rod are heated, they begin to vibrate more. Vibrating particles collide within sticking particles making them vibrate more rapidly too and transferring the energy along the bar. The particles in the petroleum jelly also get bumped into and vibrate more, and this causes the petroleum jelly to liquefy and drop the drawing pins.
Time of each pins to drop
1st - 3 seconds
2nd - 8 seconds
3rd - 13 seconds
4th - 13 seconds
5th - 13 seconds
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