Heat Conductivity

heatcond2

Equipment:

  • Metal Rod Apparatus
  • Wax
  • Five glass or steel balls
  • Bunsen burner
  • Striker
  • Beaker with hot water
  • gas hose
  • Piece of cardboard for wax balls to fall on

Demo:

Five spokes composed of metals with different heat conductivities are mounted on a central hub. Metal or glass balls are attached to the end of each rod by wax and a Bunsen burner is placed below the hub (see picture to right). The balls will fall in sequence, according to heat conductivity of each individual rod.

The spokes have labels and heat conductivities as follows:

Tin [Sn] – 63.2

Brass [B] – 109

Copper [C] – 385

Aluminum [A] – 205

Steel [S] – 50.2

 

Explanation:

Thermal conductivity is the property of a material to conduct heat. The copper rode will drop its ball first because it has a high thermal conductivity of 385.0 (W/m*K). The steel rode will drop last since it has a very low thermal conductivity of 50.2 (W/m*K).

Note: Watch out, when the balls drop they can spray hot wax. Use hot water bath (30 – 40 seconds) to soften the wax