Year 8 Science · Unit 3 · Lesson 7
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Learning Goals
Compare two (and three!)
Complete the table to compare filtration, distillation, and chromatography as separation techniques.
| Feature | Filtration | Distillation | Chromatography |
|---|---|---|---|
| What type of mixture does it separate? | |||
| What physical property is exploited? | |||
| Key lab equipment needed | |||
| One everyday or industrial example | |||
| Can it separate dissolved solids from liquid? (Yes/No) |
Real-world context
In 2024, a team of Australian geologists working near Kalgoorlie, Western Australia, collected a water sample from an abandoned gold mine. Laboratory analysis confirmed the sample contained two types of contaminants: dissolved gold compounds (gold in ionic form, invisible to the naked eye) and suspended fine clay particles that made the water look cloudy. The team needed to extract both the clay and the gold compounds separately for analysis.
(a) Plan a two-step separation sequence for this water sample. Name the technique for each step and explain why each technique is appropriate for what it is separating.
(b) Why would using filtration alone fail to separate the gold compounds from the water? Use the idea of particle size in your answer.
1. A forensic scientist at the Australian Federal Police laboratory wants to identify the dyes in an ink sample taken from a forged document. Which separation technique should they use, and why is it better than evaporation for this task?
2. CSIRO engineers are developing a process to extract fresh water from seawater for drought-affected communities. Explain which separation technique is most appropriate and what happens to the salt during this process.
Wrap Up
In one sentence, what was the main idea of this lesson?