Heat transfer - CCEAInvestigation - Prescribed Practical P3

Conclusion

The drawing pin fell off the copper rod in the shortest time followed by the aluminium and then the iron.

The glass rod is last.

The glass rod should be removed from the heat approximately 30 seconds after the pin falls off the iron to prevent the glass from melting.

From this we can conclude that copper conducts heat energy better than aluminium, while aluminium conducts better than iron and glass.

We say that copper has a high thermal conductivity.

This agrees with our prediction.

We can now also conclude that the non-metal, glass, is a very poor conductor of heat.

Evaluation

To ensure the reliability of the investigation the method should be repeated to check that the pins fall off the rods in the same order.

An average time could be calculated.

A way of improving the accuracy of this investigation would be to use temperature probes attached to the end of each rod and connected to a data logger.

The time could then be recorded for each rod to reach the same temperature, for example, 50^oC.

The rods could be heated by placing them into a water bath maintained at 90 ^oC.

This would help to ensure even heating of the rods.

Thermal conductivity

The material that heats the quickest in the above investigation is said to have a high thermal conductivity.

Thermal conductivity is measured in W/m/^oC (watts per metre per degree Celsius).

Some typical values of conductivities are:

The higher the thermal conductivity the better the conductor.

Copper is a good conductor of heat, air is a poor conductor of heat.

Generally, metals have high thermal conductivity and are good conductors; non-metals have low thermal conductivity and are poor conductors.

Insulating houses

When trying to keep houses warm, the choice is between materials that are poor conductors such as brick, wood, plastic and glass.

A house built of conducting materials like copper would be very cold to live in as energy would be able to leave the house easily.