Week- 9 Presentation 1 Conduction of Heat 1

Lesson Objectives: i. Understand Heat transfer ii. Understand Conduction and carryout an experiment 2

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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… 4

Steel Bridge Plastic container 5

Metal hammer head Diamond ring 6

Fishing rod Leather belt 7

ladder Metal scaffolding 8

window 9

towelling Paper towels/tissues 10

Elastic band Stretch fabric 11

springs 12

Conductors and Insulators of Heat 1.Some Materials let Heat pass through them Easily 1)These materials are called THERMAL CONDUCTORS 2)METALS are good THERMAL CONDUCTORS 3)Because heat passes through them quickly – metal normally feels COLD 13

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 14

2) Plastic, cork, wood and fabrics are good THERMAL INSULATORS 3) Thermal insulators are good for keeping heat OUT as well as IN Thermos Does both Polystyrene cup – keeps heat in Fridge – keeps heat out 15

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Week- 9 Presentation 1 Conduction of Heat 18

Heat Transfer 19

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. 21

Conduction  Heat travels at different speed through different materials. wood did not drop copper 14 s steel 73 s aluminium 16 s 22

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 24

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. 25

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Experiment diagram 27