Year 7 Science · Unit 2 · Lesson 4

Pure Substances vs Mixtures

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Learning Goals

Compare two

Complete the table to compare homogeneous mixtures and heterogeneous mixtures.

FeatureHomogeneous MixtureHeterogeneous Mixture
Can you see the different parts?
Is every scoop from the mixture identical?
Give one Australian example
What does a particle diagram look like?
Is it easier or harder to separate?

Order the steps

Number the events from 1 to 7 to show the correct order for separating a heterogeneous mixture (beach sand + iron filings + water) using filtration followed by evaporation. Event 1 = what happens first.

OrderStep
Allow the remaining liquid to evaporate slowly in a warm place, leaving any dissolved solids behind.
Pour the mixture slowly through the filter paper — the liquid passes through, the solid stays on the paper.
Set up the funnel with a cone of filter paper inside it, placed over a collection beaker.
Collect the mixture of beach sand, iron filings and water in a beaker.
Hold a magnet near the dry solid to remove the iron filings, which are attracted to the magnet.
Remove the filter paper containing the solid residue and allow it to dry.
Identify the components of the mixture (sand, iron filings, water) and choose appropriate separation methods.

1. Bushfire smoke is a mixture of air, soot particles, water vapour and gases. Is it homogeneous or heterogeneous? Justify your answer using the "teaspoon test" from the lesson.

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2. Raw eucalyptus oil from steam distillation contains oil and water. Explain why this is a mixture, not a pure substance, and suggest how you could separate the two parts.

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Wrap Up

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