Who this is for: Cambridge IGCSE Chemistry (0620) students who confuse elements, compounds and mixtures — or pick the wrong separation technique in exam questions.
What query it owns: how to understand and revise elements, compounds and mixtures in Cambridge IGCSE Chemistry.
Why this is safe: this page owns the definitions-and-separation revision-guide angle, while Tutopiya’s Elements, Compounds and Mixtures subtopic page owns the learning resource and the free Elements, Compounds and Mixtures quiz owns the practice.

An element contains only one type of atom; a compound contains two or more elements chemically combined in fixed proportions; a mixture contains two or more substances not chemically combined. These definitions underpin the entire Atoms, Elements and Compounds unit in Cambridge IGCSE Chemistry (0620). This guide covers the distinctions, separation techniques, and exam command words that cost marks.

Key takeaways

• Element — one type of atom only; compound — chemically combined, fixed ratio, properties differ from elements; mixture — physically combined, variable composition.
• Compounds need chemical methods to separate; mixtures use physical methods (filtration, distillation, chromatography).
• Filtration separates insoluble solid from liquid; distillation separates liquids by boiling point; chromatography separates dissolved substances.
• Define answers need syllabus-precise wording — “chemically combined” for compounds.
• Confirm with the Elements, Compounds and Mixtures quiz.

What are elements, compounds and mixtures?

An element is a substance that cannot be broken down into simpler substances by chemical means. A compound is a substance formed when two or more elements are chemically bonded in fixed proportions. A mixture consists of two or more substances physically combined with no chemical bonding between them.

Full notes and diagrams are on Tutopiya’s Elements, Compounds and Mixtures subtopic page.

Element vs compound vs mixture — comparison table

Feature	Element	Compound	Mixture
Composition	One type of atom	Two+ elements, fixed ratio	Two+ substances, any ratio
Separation	Cannot split chemically	Chemical methods needed	Physical methods
Properties	Unique to element	Different from constituent elements	Retains component properties
Example	Iron (Fe)	Water (H₂O)	Air, salt water

Separation techniques — summary table

Technique	Separates	Example context
Filtration	Insoluble solid from liquid	Sand from water
Crystallisation	Soluble solid from solution	Copper sulfate from solution
Simple distillation	Solvent from solution	Pure water from salt water
Fractional distillation	Liquids with different boiling points	Crude oil fractions
Chromatography	Dissolved substances	Ink pigments

How to answer elements, compounds and mixtures questions — step by step

1. Read the substance — one element type? fixed formula? physically combined?
2. For define questions, use syllabus wording — especially “chemically combined” for compounds.
3. For separation questions, identify what is being separated (solid/liquid, liquid/liquid, dissolved solutes).
4. Name the technique and state what each fraction/residue is.
5. Test with the free Elements, Compounds and Mixtures quiz.

Past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical stem
Define	Precise definition	”Define a compound.”
State	Short fact	”State one difference between a compound and a mixture.”
Describe	How a technique works	”Describe how filtration separates a mixture.”
Explain	Why a method is chosen	”Explain why fractional distillation is used for crude oil.”

Worked exam-style stems (how to answer the wording)

1. “Define a mixture.” Target: a substance containing two or more elements or compounds that are not chemically combined. Define = include “not chemically combined”.
2. “A student has a mixture of sand and salt water. Describe how to obtain pure sand and pure salt.” Target: filtration to remove sand; evaporate/crystallise salt from filtrate (or distil water first). Describe = ordered steps with named techniques.
3. “State whether air is an element, compound or mixture. Explain your answer.” Target: mixture — contains nitrogen, oxygen and other gases physically combined, variable composition. State + explain = classification then reason.

Practise more on the Atoms, Elements and Compounds topical past paper questions.

How this subtopic connects to atomic structure

Once you can classify substances, move to Atomic Structure and the Periodic Table to understand what atoms and electrons explain about elements and bonding. The Cambridge IGCSE Chemistry resource hub links every Atoms subtopic.

Common mistakes students make

• Calling salt water a compound — it is a mixture (salt dissolved in water).
• Using filtration to separate dissolved salt from water — need distillation or crystallisation.
• Omitting “chemically combined” in compound definitions.
• Confusing element (one atom type) with atom (smallest particle of an element).
• Skipping the Elements, Compounds and Mixtures quiz.

When you need more support

If separation-technique questions keep scoring partial marks, drill the topical past paper questions and book a Cambridge IGCSE Chemistry tutor.

Frequently asked questions

Is air a compound or mixture? A mixture — nitrogen, oxygen and other gases are physically combined with variable proportions.

Can compounds be separated by filtration? No — filtration separates insoluble solids from liquids in mixtures; compounds need chemical methods.

What is the difference between simple and fractional distillation? Simple distillation separates a solvent from a solution; fractional distillation separates liquids with different boiling points.

How do I revise elements, compounds and mixtures effectively? Learn definitions, practise separation stems, take the subtopic quiz, then move to atomic structure.

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