Year 7 Science · Unit 2 · Lesson 12
Challenge Worksheet
Learning Goals
Design a mini-experiment
A geologist in Western Australia has found two shiny, gold-coloured rocks. One may be real gold (Au, 79 protons) and the other may be iron pyrite — "fool's gold" — which is made of iron (26 protons) and sulfur (16 protons). Real gold is a pure element; iron pyrite is a compound. The geologist wants to use a particle detector to confirm which is which. Plan the investigation below.
| Research question | How can we use atomic structure to distinguish gold from iron pyrite? |
| What I will change (independent variable) | |
| What I will keep the same (controlled variables — list 3) | |
| What I will measure (dependent variable) | |
| My prediction — how will the detector reading differ between gold and pyrite? | |
| How I would know if my prediction is wrong | |
| One limitation of this experiment |
1. Gold (Au) has 79 protons. Iron pyrite (FeS₂) contains iron with 26 protons and sulfur with 16 protons. Explain why a particle detector that can count proton numbers could reliably tell the difference between gold and iron pyrite at the atomic level. Include what information about the atoms would be different between the two substances.
2. A classmate suggests that instead of counting protons, you could identify the gold by weighing the rocks — "gold is heavier, so the heavier rock must be gold." Evaluate this method. Is it reliable? What atomic knowledge tells us that mass alone might not be enough to identify an element?
Wrap Up
In one sentence, what was the main idea of this lesson?