S3.6.2 For the adult
Pure substances and mixtures
A bottle says pure spring water, and the water is clear. Would a scientist call it pure?
What this chapter teaches
In science, a pure substance is only one thing: an element or a compound. A mixture has two or more substances that are not joined, and each keeps its own properties. Clear things, like air and sea water, can still be mixtures.
Three questions to ask
There is no one right wording. Listen for the idea.
- What does pure mean to a scientist?
- Why is air a mixture and not one gas?
- If sea water is clear, how do you know it is not pure?
After the chapter, the learner can
- Tell a pure substance from a mixture
- Explain why sea water and air are mixtures
What they copy into their notebook
A pure substance is only one thing. A mixture has two or more things not joined. Clear does not mean pure. Air and sea water are mixtures.