Year 9 Science · Unit 2 · Lesson 02

Physical Properties of Materials

Challenge Worksheet

Name

Date

Class

Learning Goals

Distinguish between hardness and tensile strength using clear examples
Communicate scientific concepts accurately to a non-expert audience
Evaluate complex material trade-offs using multiple physical properties

Go Deeper

Explain it to a Year 7 student

A Year 7 student is confused about the difference between hardness and tensile strength. Use the sentence starters below to explain both concepts clearly. Use real everyday examples to help.

"Hardness measures how well a material resists…"

"Tensile strength is different because it measures…"

"A good example that shows why they're not the same is glass, which…"

"When engineers choose materials, they need to know both because…"

Show What You Know

1. A student claims: "You can always replace steel with a lighter material to make a structure better." Use at least TWO specific physical properties from this lesson to explain why this trade-off is more complex than simply swapping materials.

Challenge 4 marks

2. The Harbour Bridge in Sydney is made from steel, not aluminium, even though aluminium is lighter and does not rust. Using the physical properties you have learned, construct an argument that explains why steel is the better choice for a large suspension bridge, and identify ONE situation where aluminium would actually be preferable.

Challenge 4 marks

Wrap Up

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