Week- 9 Presentation 1

Conduction of Heat

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Lesson Objectives:

i. Understand Heat transfer

ii. Understand Conduction and carryout an experiment

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Comparing Materials

Materials have certain PROPERTIES which make them USEFUL

We need to be able to describe and compare the properties of a material and say why its used for a job. We use certain materials for certain jobs…

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Steel Bridge

Plastic container

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Metal hammer headDiamond ring

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Fishing rod

Leather belt

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ladder Metal scaffolding

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window

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towellingPaper towels/tissues

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Elastic bandStretch fabric

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springs

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Conductors and Insulators of Heat1. Some Materials let Heat pass

through them Easily1) These materials are called

THERMAL CONDUCTORS2) METALS are good THERMAL

CONDUCTORS3) Because heat passes through

them quickly – metal normally feels COLD

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Some Materials Do Not let Heat pass through them

1) Materials that do not let heat pass through them are called THERMAL INSULATORS.

Wooden handle

Oven glove

thermals

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2) Plastic, cork, wood and fabrics are good THERMAL INSULATORS

3) Thermal insulators are good for keeping heat OUT as well as IN

ThermosDoes both

Polystyrene cup – keeps heat in

Fridge – keeps heat out

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Week- 9 Presentation 1Conduction of Heat

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Heat Transfer

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Heat Transfer

Heat travels from a region of higher temperature to a region of lower temperature.

This process is carried out by Conduction Convection Radiation

When thermal equilibrium is reached in all regions, there is no net heat transfer. 20

Conduction

Conduction is the process in which heat is transferred through a medium (solid) from one particle to the next.

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Conduction

Heat travels at different speed through different materials.

wood did not drop copper 14 s steel 73 s aluminium 16 s

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Conduction Good heat conductors have high heat

conductivity, e.g. Copper and Silver. Generally, all substances can conduct

heat, But some are exceptionally bad conductors e.g. air and gases or non-metals.

Poorest Conductor – Vacuum Poor Conductors are also called

Insulators.23

Insulation of Heat Conduction

To reduce heat conduction, insulators are used.

The poorest conductors are used as heat insulators where applicable.

Insulation is found in the walls of the home, on heating pipes and air-con pipes (pipe lagging),

Winter clothing or the sweater that you wear

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Fibreglass Insulation Glass is a poor conductor. Fibreglass

uses this property. Layers are placed between walls to

reduce heat conducted into the house in summer or conducted out of the house in winter.

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Experiment diagram

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