Thermal conductivity

AimTo be able to compare the thermal conductivities of a range of materials.

ConductionHeat energy can be transferred by conduction. When materials are heated, the atoms vibrate more. This kinetic energy can be passed from atom to atom in conducting materials. Conduction happens in all materials, but in good conductors like metals, free electrons can transfer the heat energy more quickly. All metals are good conductors of heat. Insulators do not have free electrons and conduct heat poorly. Explain why metals always feel cold to the touch, whereas wood for example feels warm ?

Conduction:

Direction of heat transferHot Cold

Conduction Conduction of heat energy

Diagram

Notes Heat energy is transferred by vibrating atoms passing on their kinetic energy to adjacent atoms. Metals are good conductors because of their free electrons and high density.

In this picture, heat is conducted and transferred by conduction. Heat energy spreads out from the hot or warm regions (coloured in red) to colder regions (coloured in blue)

In a piece of metal, all the atoms lose their outer electrons. These negative electrons move around between positive metal ions. Metals are good at conducting electricity and heat because of the free electrons which are able to move around.

++

++

-

-

-

-

++

++

-

-

-

-

++

++

-

-

-

-

++

++

-

-

-

-

++

++

-

-

-

-

++

++

-

-

-

-

Equipment

Diagram

Materials, petroleum jelly, drawing pins, stop clock, safety glasses, tripod, heat mat, Bunsen burner

Method

1. Attach drawing pin, a measured distance from end of first material using petroleum jelly.

2. Place the material on a tripod3. Heat the other end using a bunsen.4. Time until petroleum jelly melts, and pin drops off.5. Repeat twice with same material (cool it first)6. Repeat with other materials

Risk Assessment

Risk:

Hazard:

Control Measure:

Results

Material Time 1(s) Time 2 (s) Time 3 (s) Ave time (s)

Copper

Aluminium

Brass

Steel

glass

Analysis

Conductivity is…

Evaluation

My experiment went…

I did not have problems with… because…

I had problems with … because…

To improve my experiment I could…

My results would be more reliable if I…

I liked this experiment because…

I disliked this experiment because…