AQA · Chemistry · 8462
GCSE Chemistry: Pure substances
Chemical analysis · AQA GCSE Chemistry (8462), specification point 4.8.1.1. Cards are generated from the exam board's own specification for "Pure substances", and every card links back to the page it came from. Specification © AQA — used with attribution.
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In chemistry, what is a pure substance?
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A single element or compound, not mixed with any other substance.
In chemistry, a pure substance is a single ?, not mixed with any other substance.
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element or compound
At what temperatures do pure elements and compounds melt and boil?
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At specific (sharp, fixed) temperatures.
Which data can be used to distinguish a pure substance from a mixture?
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Melting point and boiling point data.
How does the melting behaviour of a mixture differ from that of a pure substance?
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A pure substance melts at a specific temperature, whereas a mixture melts over a range of temperatures.
A sample melts sharply at exactly 80 °C. What does this suggest about its purity?
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It is likely a pure substance, because pure substances melt at a specific temperature rather than over a range.
What does 'pure' mean in everyday language, as opposed to chemistry?
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A substance that has had nothing added to it — unadulterated and in its natural state, e.g. pure milk.
Why is 'pure milk' not a pure substance in the chemical sense?
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Milk is a mixture of many compounds (water, fats, proteins, sugars), not a single element or compound.
Melting point and boiling point data can be used to distinguish pure substances from ?.
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mixtures
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