Year 9 Science · Unit 2 · Lesson 02
Challenge Worksheet
Learning Goals
1. A Year 7 student is confused about hardness and tensile strength. Finish each sentence starter to explain both ideas, using everyday examples.
“Hardness measures how well a material resists …”
“Tensile strength is different because it measures …”
“Glass shows they are not the same, because glass …”
Class investigation: mass and volume
Students weighed five aluminium samples of different sizes and found each one’s volume by water displacement.
| Volume (cm³) | 2.0 | 4.0 | 6.0 | 8.0 | 10.0 |
|---|---|---|---|---|---|
| Mass (g) | 5.5 | 10.7 | 16.3 | 21.5 | 27.1 |
Source: sample class results.
2. Plot mass against volume. Label both axes with units and draw a line of best fit through the origin.
3. Use two points far apart on your line to calculate its gradient. What property of aluminium does the gradient give?
Answer g/cm³
4. A 12 cm³ block of steel (density 7.9 g/cm³) and a 40 cm³ block of aluminium sit on a bench. Calculate the mass of each (use your density from Question 3 for aluminium). What do your answers show about the claim “denser materials are always heavier”?
Steel g
Aluminium g
5. The points in Table 1 do not lie exactly on a straight line. Suggest one cause, and one change to the method that would reduce it.
6. The Sydney Harbour Bridge, a steel arch bridge, is made from steel, not aluminium, even though aluminium is much less dense and does not rust. A student says you can always replace steel with a lighter material to make a structure better. Using physical properties from this lesson, argue why steel is the better choice for a large bridge, and identify ONE situation where aluminium would be the better choice.