2.1

Elements, compounds and mixtures

Cambridge IGCSE Chemistry (0620)  · Unit 2: Atoms, elements and compounds  · 11 flashcards

Elements, compounds and mixtures is topic 2.1 in the Cambridge IGCSE Chemistry (0620) syllabus , positioned in Unit 2 — Atoms, elements and compounds , alongside Atomic structure, Bonding and Structure and properties.  In one line: An element is a substance made of only one type of atom. It cannot be broken down into simpler substances by chemical means.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across undefined questions worth 244 marks (around 3.8% of all Chemistry marks in those years).

The deck below contains 11 flashcards — 3 definitions, 3 key concepts and 5 identification cards — covering the precise wording mark schemes reward.  Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

An element

An element is a substance made of only one type of atom. It cannot be broken down into simpler substances by chemical means.

Example: Gold (Au) is an element.

What the Cambridge 0620 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe the differences between elements, compounds and mixtures
Definition Flip

Define an element.

Answer Flip

An element is a substance made of only one type of atom. It cannot be broken down into simpler substances by chemical means.

Example: Gold (Au) is an element.
Definition Flip

Define a compound.

Answer Flip

A compound is a substance formed when two or more elements are chemically bonded together in a fixed ratio.

Example: Water (H₂O) is a compound formed from hydrogen and oxygen.
Definition Flip

Define a mixture.

Answer Flip

A mixture is a substance comprising two or more elements or compounds that are physically mixed but not chemically combined.

Example: Air is a mixture of nitrogen, oxygen, and other gases.
Key Concept Flip

What is the key difference between a compound and a mixture?

Answer Flip

In a compound, elements are chemically bonded in a fixed ratio, whereas in a mixture, elements or compounds are physically mixed and not chemically bonded. Mixtures don't have a fixed ratio.

Key Concept Flip

Give an example of a homogeneous mixture.

Answer Flip

A homogeneous mixture has uniform composition throughout.

Example: Saltwater is a homogeneous mixture because the salt is evenly distributed in the water.
Key Concept Flip

Give an example of a heterogeneous mixture.

Answer Flip

A heterogeneous mixture has a non-uniform composition.

Example: Sand and water form a heterogeneous mixture because the sand settles and is not evenly distributed.
Key Concept Flip

How can a mixture be separated?

Answer Flip

Mixtures can be separated by physical methods like filtration, evaporation, distillation, or magnetism, which do not involve chemical reactions.

Example: Iron filings can be separated from sand using a magnet.
Key Concept Flip

How are compounds formed?

Answer Flip

Compounds are formed through chemical reactions where atoms share or transfer electrons, resulting in chemical bonds.

Example: Sodium (Na) reacts with Chlorine (Cl) to form Sodium Chloride (NaCl) through ionic bonding.
Key Concept Flip

Is air an element, compound, or mixture?

Answer Flip

Air is a mixture. It's composed primarily of nitrogen and oxygen, along with smaller amounts of other gases such as argon and carbon dioxide, which are not chemically bonded.

Key Concept Flip

Is water (H₂O) an element, compound, or mixture?

Answer Flip

Water (H₂O) is a compound. It is formed by the chemical bonding of two hydrogen atoms and one oxygen atom in a fixed ratio.

Key Concept Flip

Is oxygen (O₂) an element, compound, or mixture?

Answer Flip

Oxygen (O₂) is an element. It is composed of only one type of atom: oxygen. Two oxygen atoms bond covalently to form a diatomic molecule. Oxygen is in Group 6 of the Periodic Table.

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1.2 Particle theory 2.2 Atomic structure

Key Questions: Elements, compounds and mixtures

Define an element.

An element is a substance made of only one type of atom. It cannot be broken down into simpler substances by chemical means.

Example: Gold (Au) is an element.
Define a compound.

A compound is a substance formed when two or more elements are chemically bonded together in a fixed ratio.

Example: Water (H₂O) is a compound formed from hydrogen and oxygen.
Define a mixture.

A mixture is a substance comprising two or more elements or compounds that are physically mixed but not chemically combined.

Example: Air is a mixture of nitrogen, oxygen, and other gases.

Tips to avoid common mistakes in Elements, compounds and mixtures

More topics in Unit 2 — Atoms, elements and compounds

Elements, compounds and mixtures sits alongside these Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

2.2 Atomic structure

12 flashcards
2.3 Bonding

1 flashcards
2.4 Structure and properties

9 flashcards

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0620 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

element compound mixture atom molecule pure substance impure physical change chemical change separation filtration evaporation distillation fractional distillation chromatography crystallisation

Key terms covered in this Elements, compounds and mixtures deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

An element
A compound
A mixture

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How to study this Elements, compounds and mixtures deck

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