AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
A mixture consists of two or more elements or compounds not chemically…
Full specification wording
Mixtures: A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.
A mixture contains two or more substances not joined by chemical bonds.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 1 of 4
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A mixture contains two or more substances not joined by chemical bonds. The substances can be elements, compounds or both, and they keep their own chemical properties. For example, air is a mixture of nitrogen, oxygen, argon and carbon dioxide. Each gas behaves as it would on its own; oxygen still supports combustion, while nitrogen remains largely unreactive. The components of a mixture can be separated by physical methods such as filtration or distillation because no chemical bonds are broken. In contrast, a compound has a fixed composition and its elements are chemically combined, so its properties differ from those of the original elements. This distinction is assessed by asking you to identify mixtures and describe separation methods.
What earns the marks
- A mixture contains two or more elements or compounds that are not chemically combined.
- The substances in a mixture can be present in any proportion, unlike a compound which has a fixed composition.
- Each substance in a mixture retains its own chemical properties.
- Mixtures can be separated by physical processes because no chemical bonds are broken.
- Examples of mixtures include air, seawater, alloys and crude oil.
Common mistakes and how to put them right
Thinking that a mixture has fixed proportions.
Put it right: The proportions in a mixture can vary, while a compound has a fixed ratio of elements.
Confusing mixtures with compounds.
Put it right: Seawater is a mixture of water and dissolved salts; the ions are not chemically bonded to water molecules.
Believing that chemical properties change when substances are mixed.
Put it right: Each substance keeps its chemical properties in a mixture.
Exam tips
- When asked to distinguish a mixture from a compound, refer to chemical combination and fixed composition.
- Use a named separation technique to support your answer, such as filtration for a solid–liquid mixture or distillation for a solvent–solute mixture.
Try the lesson
The start of the Mixtures: A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement describes a mixture?
Listen
A mixture contains two or more substances not joined by chemical bonds. The substances can be elements, compounds or both, and they keep their own chemical properties. For example, air is a mixture of nitrogen, oxygen, argon and carbon dioxide. Each gas behaves as it would on its own; oxygen still supports combustion, while nitrogen remains largely unreactive. The components of a mixture can be separated by physical methods such as filtration or distillation because no chemical bonds are broken. In contrast, a compound has a fixed composition and its elements are chemically combined, so its properties differ from those of the original elements. This distinction is assessed by asking you to identify mixtures and describe separation methods. A strong answer earns marks for these points. A mixture contains two or more elements or compounds that are not chemically combined. The substances in a mixture can be present in any proportion, unlike a compound which has a fixed composition. Each substance in a mixture retains its own chemical properties. Mixtures can be separated by physical processes because no chemical bonds are broken. A common slip: Thinking that a mixture has fixed proportions: for example, saying that air always contains exactly 20% oxygen. Instead, the proportions in a mixture can vary, while a compound has a fixed ratio of elements. Exam tip: When asked to distinguish a mixture from a compound, refer to chemical combination and fixed composition.
Key words
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Mixture
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Conservation of chemical properties in physical mixtures
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Separation techniques based on physical differences
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See every definition
- Mixture
- Consists of two or more elements or compounds not chemically combined together.
- Conservation of chemical properties in physical mixtures
- The chemical properties of each substance in the mixture are unchanged.
- Separation techniques based on physical differences
- Components of a mixture can be separated by physical methods such as filtration or distillation because no chemical bonds are broken.
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