Year 9 Science · Unit 3 · Lesson 8

Conduction, Convection and Radiation

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Learning Goals

Warm Up

Read the graph

The bar chart below shows the thermal conductivity of five common materials measured in watts per metre per kelvin (W/m·K). A higher value means heat passes through the material more easily.

0 100 200 300 400 385 205 1.1 0.7 0.024 Copper Aluminium Glass Brick Air Thermal Conductivity of Common Materials (W/m·K)

Data: Engineering Toolbox (2003); values at ~25°C

(a) Rank the five materials from best insulator to worst insulator (i.e., from lowest to highest thermal conductivity).

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(b) Fibreglass roof insulation batts used in Australian homes work by trapping millions of tiny air pockets. Using the graph data, predict why trapped air provides better insulation than solid glass or solid brick.

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(c) Why is copper used in the base of good quality saucepans sold in Australian kitchenware stores, rather than glass or brick? Use thermal conductivity data in your answer.

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Your Turn

Because… chain

Fill in the missing effects. Each cause leads to the next step in explaining how the sea breeze forms in coastal Australian cities like Perth, Sydney, and Adelaide on hot summer days.

On a hot summer day, sunlight (radiation) heats the land surface faster than the ocean.
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The warm air above the hot land expands, becomes less dense, and rises, creating a convection current.
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The cooler, denser air from over the ocean moves in toward the land to replace the rising warm air.
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This continuous circulation of air, warm rising over land, cool flowing in from sea, becomes a sustained breeze.
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Overall outcome: What does the sea breeze demonstrate about convection?

Show What You Know

1. Solar hot water systems on Australian rooftops use sunlight to heat water. Identify all three heat transfer methods involved in the operation of one of these systems, and describe the role each one plays.

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Wrap Up

In one sentence, what was the main idea of this lesson?

HSCScience · Year 9 Science · Unit 3 · Lesson 8 · Apply Worksheet