Prescribed practical P3 - heat transfer
Comparing the heat conductivity of different materials by measuring the time it takes heat to travel through a variety of conductors and at least one insulator.
Variables
In this experiment:
- the Independent Variable is the material of the conducting rod.
- the Dependent Variable is the time taken for the pin to drop off.
- the Control Variables are the length and cross section area of each conducting rod, the mass of the drawing pin and the amount of Vaseline used to attach the pin to each rod.
The control variables are kept the same by:
- Ensuring each rod is the same length and has the same cross section area.
- Ensuring that the same region of each rod is in the Bunsen flame.
- Attaching the pin at the end of each rod.
- Using the same amount of Vaseline to attach each pin.
- Using identical pins.
Remember - these variables are controlled (or kept the same) because to make it a fair test, only one variable can be changed, which in this case is the material of the conductor.
Prediction
Metals will conduct faster than non-metals and some metals will conduct faster than other metals.
Justification for the prediction
Different metals have different properties, for example different density, and so they will not all conduct heat energy at the same rate.
Risk assessment
| Hazard | Consequence | Control measures |
| The Bunsen flame is very hot. | Burn skin. Damage to eyes. |
|
| The Bunsen flame could start a fire. | Hair singed or set alight. Paper set on fire. |
|
| The tripod, Bunsen burner and conducting rods become hot. | Burn skin. |
|
| The conducting rods could fall off the tripod. | Falling hot rods could burn lap, legs and arms. |
|
| Hazard | The Bunsen flame is very hot. |
|---|---|
| Consequence | Burn skin. Damage to eyes. |
| Control measures |
|
| Hazard | The Bunsen flame could start a fire. |
|---|---|
| Consequence | Hair singed or set alight. Paper set on fire. |
| Control measures |
|
| Hazard | The tripod, Bunsen burner and conducting rods become hot. |
|---|---|
| Consequence | Burn skin. |
| Control measures |
|
| Hazard | The conducting rods could fall off the tripod. |
|---|---|
| Consequence | Falling hot rods could burn lap, legs and arms. |
| Control measures |
|
Apparatus
A Bunsen burner, tripod, bench mat, identical copper, aluminum, iron and glass rods, a stop clock, four identical drawing pins, Vaseline, a gas lighter, safety glasses, tongs and/or heat proof gloves.
Diagram
Method
- Fix the drawing pin to the end of each rods using identical spots of Vaseline.
- Arrange the rods carefully on top of the tripod. They could rest on a heat proof mat if necessary.
- Position the other end of each rod over the Bunsen.
- Using the gas lighter, light the Bunsen flame and adjust the hole to half open.
- Start the stop clock.
- Record the time taken for the wax to melt and the drawing pin to drop off each rod in a suitable table.
The fastest time shows the best conductor of heat.
Avoiding errors
Ensure that the Bunsen flame heats the same part of each rod and that each rod is evenly in the flame.
Results
| Material | Time taken for pin to fall off in seconds |
| Aluminium | |
| Copper | |
| Glass | |
| Iron |
| Material | Aluminium |
|---|---|
| Time taken for pin to fall off in seconds |
| Material | Copper |
|---|---|
| Time taken for pin to fall off in seconds |
| Material | Glass |
|---|---|
| Time taken for pin to fall off in seconds |
| Material | Iron |
|---|---|
| Time taken for pin to fall off in seconds |
Graph
Draw a bar chart with Time in seconds on the y-axis and Material on the x-axis.
Give the graph a suitable title.