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Conductors and conduction
Objects with thermal energy can transfer their thermal energy to other objects that are directly touching it. The transfer of heat (thermal energy) between two objects that are touching each other is called conduction.
Conduction
- With conduction, heat transfers from a hot object to a cold object. In fact, heat ALWAYS transfers from hot to cold.
- No material or matter moves when heat is transferred by conduction.
Conductors
- Some materials conduct or transfer heat better or more efficiently than others. Materials that conduct heat well are called conductors.
- Metals, including silver, aluminium and copper are excellent conductors.
- Stainless steel is a good conductor too. In fact, many pots and pans are made of stainless steel because it conducts heat well to cook food.
Insulators
- Some materials do NOT conduct heat well or efficiently. These materials are called insulators.
- Rubber, plastic, air and glass are good insulators. Often, these materials are used to prevent the conduction of heat between objects.
*Good conductors are poor insulators
*Good insulators are poor conductors
Thermal vs. Electrical Conductors and Insulators
- Good thermal conductors are often good electrical conductors. These materials allow thermal or electrical energy to pass easily.
- Good thermal insulators are often good electrical insulators. These materials do not allow thermal or electrical energy to pass easily.
Activity: Thermal conductivity #1
Make a prediction of which metal, (Steel, Brass, Aluminium or copper), you think will conduct heat the best. Record your prediction in your exercise book.
Full Thermosmart instructions are attached at the bottom of this page.
Carefully pour hot water from the kettle into a 250 cm3 beaker.
Suspend the conduction bars from a clamp and stand so that only the bottom of each bar is submerged in the water.
Observe which metal conducts heat the best.
Record this conclusion and compare it to the prediction you made at before the experiment.
Activity: Thermal conductivity #2
An experiment can be used to investigate which metal is the best conductor of heat. It involves some long thin strips of different metals (eg steel, aluminium and copper), wax, drawing pins and a Bunsen burner.
Full Heat Conductometer instructions are attached at the bottom of this page.
Method:
Fix the drawing pin to the end of the metal strip using drops of wax/vaseline.
Position the other end of the metal strip into a Bunsen flame.
Record the time taken for the wax to melt and the drawing pin to drop off.
The fastest time shows the best conductor of heat.
Variables that affect the time taken for the drawing pins to fall include the distance they are from the flame and the thickness of the metal.
Review:
Use the information and diagrams on this BBC Bitesize page to help you review what we have learnt today.
Use a whiteboard to produce diagrams that show how substances conduct thermal energy and why some materials are better conductors than others. Record your diagrams and explanations and upload to flipgrid.