conductivity The ability of a material to allow heat to travel through it.
Electrical
conductivity The ability of a material to allow electricity to travel through it.
Conductors Substances that allow heat or electricity to flow through them.
Insulators
Substances that do not allow heat or electricity to flow
through them.
There are two kinds of conductivity. Thermal conductivity is the ability of a material to allow heat to travel through it. Electrical conductivity is the ability of a material to allow electricity to travel through it. Materials that allow heat or electricity to flow through them are called conductors. Materials
that do not allow the flow of heat or electricity through them are called insulators. Thermal conductivity
Activity To show thermal conductivity
Apparatus Retort stand, metal rod, four paper clips, some Vaseline.
Method 1. Set up the apparatus as shown in the diagram. 2. Heat one end of the metal rod as shown. 3. Record the time taken until each of the paper clips falls.
Retort stand
Vaseline
Metal rod
1 2 3 4 Paper clips
Bunsen burner
Fig. 4 Thermal conductivity of a metal rod.
Questions In what order do the paper clips fall? Suggest a reason why the paper clips fall at different times.
Activity To test the thermal conductivity of a variety of materials.
Apparatus Beaker, metal rod, plastic rod, wooden rod, Bunsen burner
Method 1. Bring some water to the boil in a beaker using a Bunsen burner.
2. Turn off the Bunsen burner. 3. Place the three rods into the water as shown. 4. After five minutes, touch each of the rods and note how hot they feel.
5. If a digital thermometer is available you can strap it to the top of each rod and record the temperature.
230
Fig. 5 Thermal conductivities of different materials.
Questions Was there a difference in the temperatures of the rods? Why do you think this is?
