Year 7 Science · Unit 2 · Lesson 3
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Learning Goals
Read the graph — Density of common materials
Study the bar chart showing the density of five materials, then answer the questions below.
Data: Engineering Toolbox, 2024
(a) Which of the five materials would float in water? Explain how you know, using their density values.
(b) Copper is about how many times denser than aluminium? Show your working.
(c) A student says: "The heaviest material is always the densest." Is this correct? Use the graph to explain your answer.
Scenario
A scientist at the CSIRO Materials Science laboratory in Clayton, Victoria, has discovered an unknown solid substance. She measures four of its physical properties. Her results are shown in the table below. Using the property reference table, identify the most likely substance.
| Property measured | Unknown substance result |
|---|---|
| Density | 2.70 g/cm³ |
| Electrical conductivity | Good conductor |
| Thermal conductivity | Good conductor |
| Solubility in water | Does not dissolve |
| Substance | Density (g/cm³) | Elec. conductor? | Dissolves in water? |
|---|---|---|---|
| Table salt | 2.16 | No (solid form) | Yes |
| Aluminium | 2.70 | Yes | No |
| Glass | 2.50 | No | No |
| Copper | 8.90 | Yes | No |
(a) Which substance does the unknown sample most likely match? Explain your reasoning by referring to at least TWO properties.
(b) Could the scientist be certain this is the correct substance based on these four properties alone? Explain what additional test she could do to be more confident.
Wrap Up
In one sentence, what was the main idea of this lesson?