AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
In everyday language, a pure substance can mean a substance that has had…
Full specification wording
Pure substances: In everyday language, a pure substance can mean a substance that has had nothing added to it, so it is unadulterated and in its natural state, eg pure milk.
Everyday language and chemistry use the word pure differently.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 4 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Everyday language and chemistry use the word pure differently. In everyday use, pure means nothing has been added, so the substance is unadulterated and in its natural state; pure milk, for example, has no added water, colouring or preservatives. In chemistry, pure means a substance that contains only one substance, with no other substances mixed in. Pure milk is a mixture of water, fats, proteins, sugars and minerals, so it is not pure in the chemical sense. When a question uses the word pure, decide from the context which meaning applies: a food label or advertisement usually uses the everyday meaning, while a melting point or boiling point investigation uses the chemical meaning. This distinction matters because the two meanings lead to different conclusions about the same sample.
What earns the marks
- In everyday language, pure means a substance has had nothing added to it and is unadulterated and in its natural state.
- Pure milk is an everyday example: it has no added substances, but it is still a mixture of several substances.
- In chemistry, pure means a substance contains only one substance and nothing else.
- The everyday meaning and the chemical meaning of pure are different, so the context of a question determines which meaning applies.
- A sample can be pure in the everyday sense while being a mixture in the chemical sense.
Common mistakes and how to put them right
Assuming pure always means the chemical meaning.
Put it right: In everyday contexts such as food labels it means unadulterated, so the context must be checked.
Describing pure milk as a pure substance in the chemical sense.
Put it right: Pure milk is a mixture of water, fats, proteins, sugars and minerals.
Believing the two meanings always agree.
Put it right: A sample can be unadulterated yet still contain several substances.
Exam tips
- Identify whether the question is using everyday or chemical language before answering.
- If the context is a food or product label, explain that pure means nothing has been added.
- If the context is a laboratory measurement, explain that pure means only one substance is present.
Try the lesson
The start of the Pure substances: In everyday language, a pure substance can mean a substance that has had nothing added to it, so it is unadulterated and in its natural state, eg pure milk. lesson, made from checked teaching notes for this specification point.
Have a go first
In everyday language, what does it mean to describe milk as pure?
Listen
Everyday language and chemistry use the word pure differently. In everyday use, pure means nothing has been added, so the substance is unadulterated and in its natural state; pure milk, for example, has no added water, colouring or preservatives. In chemistry, pure means a substance that contains only one substance, with no other substances mixed in. Pure milk is a mixture of water, fats, proteins, sugars and minerals, so it is not pure in the chemical sense. When a question uses the word pure, decide from the context which meaning applies: a food label or advertisement usually uses the everyday meaning, while a melting point or boiling point investigation uses the chemical meaning. This distinction matters because the two meanings lead to different conclusions about the same sample. A strong answer earns marks for these points. In everyday language, pure means a substance has had nothing added to it and is unadulterated and in its natural state. Pure milk is an everyday example: it has no added substances, but it is still a mixture of several substances. In chemistry, pure means a substance contains only one substance and nothing else. The everyday meaning and the chemical meaning of pure are different, so the context of a question determines which meaning applies. Exam tip: Identify whether the question is using everyday or chemical language before answering.
See it
Key words
Say what each word means before you turn the card.
Everyday versus chemical meaning
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Unadulterated substances
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Mixtures in natural products
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Context in scientific language
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See every definition
- Everyday versus chemical meaning
- In everyday language pure means a substance has had nothing added to it, while in chemistry it means a substance contains only one substance.
- Unadulterated substances
- A substance that has had nothing added to it, so it is in its natural state, as with pure milk.
- Mixtures in natural products
- Pure milk is a mixture of water, fats, proteins, sugars and minerals, so it is not pure in the chemical sense.
- Context in scientific language
- When a question uses the word pure, the context determines which meaning applies, such as a food label or a melting point investigation.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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