IGCSE Elements, Compounds and Mixtures: Complete Guide for Cambridge IGCSE Chemistry

IGCSE elements, compounds and mixtures are fundamental topics in Cambridge IGCSE Chemistry that form the basis for understanding all chemical substances. Mastering classification of matter, properties of elements and compounds, and separation techniques is essential for achieving top grades in IGCSE Chemistry exams.

This comprehensive IGCSE elements, compounds and mixtures guide covers everything you need to know, including what elements, compounds, and mixtures are, how to distinguish between them, their properties, separation methods, step-by-step worked examples, common exam questions, and expert tips from Tutopiya’s IGCSE chemistry tutors. We’ll also show you how to avoid the most common mistakes that cost students valuable marks.

🎯 What you’ll learn: By the end of this guide, you’ll know how to identify elements, compounds, and mixtures, understand their properties, explain separation techniques, and apply these concepts to solve problems in IGCSE Chemistry exams.

Already studying with Tutopiya? Practice these skills with our dedicated IGCSE Chemistry practice deck featuring exam-style questions and instant feedback.

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Why IGCSE Elements, Compounds and Mixtures Matter

IGCSE elements, compounds and mixtures are essential foundation topics in IGCSE Chemistry. Here’s why they’re so important:

• Foundation topic: Required for understanding all other chemistry concepts
• High frequency: Questions about classification appear in almost every IGCSE chemistry paper
• Exam weight: Typically worth 6-12 marks per paper
• Real-world applications: Essential for understanding materials, substances, and separation processes
• Link to other topics: Connects to atomic structure, bonding, and chemical reactions

Key insight from examiners: Students often confuse compounds with mixtures or struggle with separation techniques. This guide will help you master these concepts systematically.

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Classification of Matter

Matter can be classified into three main categories:

1. Elements - Pure substances made of one type of atom
2. Compounds - Pure substances made of two or more different elements chemically combined
3. Mixtures - Made of two or more different substances not chemically combined

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Understanding Elements

An element is a pure substance that cannot be broken down into simpler substances by chemical means.

Key Characteristics of Elements

• Made of one type of atom - All atoms have the same atomic number
• Cannot be broken down - Cannot be separated into simpler substances chemically
• Represented by symbols - e.g., H (hydrogen), O (oxygen), Fe (iron)
• Listed in Periodic Table - All known elements are organized in the Periodic Table
• Fixed composition - Always contains the same atoms

Examples of Elements

Metals:

• Iron (Fe)
• Copper (Cu)
• Gold (Au)
• Aluminum (Al)

Non-metals:

• Hydrogen (H)
• Oxygen (O)
• Carbon (C)
• Nitrogen (N)

Metalloids:

• Silicon (Si)
• Boron (B)

Properties of Elements

• Definite melting and boiling points (for pure elements)
• Fixed composition
• Cannot be separated into simpler substances
• Represented by chemical symbols

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Understanding Compounds

A compound is a pure substance made of two or more different elements that are chemically combined in fixed proportions.

Key Characteristics of Compounds

• Made of different elements - Contains two or more different types of atoms
• Chemically combined - Elements are bonded together
• Fixed composition - Always has the same ratio of elements
• Can be broken down - Can be separated into elements by chemical means
• Represented by formulas - e.g., H₂O (water), CO₂ (carbon dioxide)

Examples of Compounds

Common Compounds:

• Water (H₂O): Hydrogen + Oxygen
• Carbon dioxide (CO₂): Carbon + Oxygen
• Sodium chloride (NaCl): Sodium + Chlorine
• Magnesium oxide (MgO): Magnesium + Oxygen
• Glucose (C₆H₁₂O₆): Carbon + Hydrogen + Oxygen

Properties of Compounds

• Different properties from the elements that form them
• Fixed composition - Always the same ratio of elements
• Definite melting and boiling points
• Can only be separated by chemical reactions
• Represented by chemical formulas

Formation of Compounds

Compounds form through chemical reactions:

Example: Magnesium + Oxygen → Magnesium oxide

• 2Mg + O₂ → 2MgO
• Properties of magnesium oxide are completely different from magnesium and oxygen

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Understanding Mixtures

A mixture contains two or more different substances that are not chemically combined.

Key Characteristics of Mixtures

• Made of different substances - Can be elements, compounds, or both
• Not chemically combined - Substances are physically mixed
• Variable composition - Can have different proportions
• Can be separated - By physical methods (no chemical reactions needed)
• Properties of components retained - Each substance keeps its own properties

Examples of Mixtures

Common Mixtures:

• Air: Nitrogen + Oxygen + Other gases
• Sea water: Water + Salt + Other dissolved substances
• Bronze: Copper + Tin
• Crude oil: Many different hydrocarbons
• Salt water: Salt + Water

Types of Mixtures

1. Homogeneous Mixtures (Solutions)

• Uniform composition throughout
• Cannot see different parts - looks the same throughout
• Examples: Salt water, air, sugar solution

2. Heterogeneous Mixtures

• Non-uniform composition
• Can see different parts - distinct phases visible
• Examples: Sand and water, oil and water, granite

Properties of Mixtures

• Variable composition - Can have different proportions
• Properties of components are retained
• No fixed melting/boiling points - Can vary
• Can be separated by physical methods
• No chemical formulas - Not a single substance

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Differences Between Elements, Compounds, and Mixtures

Comparison Table

Feature	Element	Compound	Mixture
Composition	One type of atom	Two or more elements chemically combined	Two or more substances physically mixed
Separation	Cannot be broken down	By chemical reactions only	By physical methods
Properties	Properties of that element	Different from component elements	Properties of components retained
Composition	Fixed	Fixed (definite ratio)	Variable
Formula	Symbol (e.g., Fe)	Chemical formula (e.g., H₂O)	No formula
Melting/Boiling Point	Definite	Definite	Varies

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Separating Mixtures

Mixtures can be separated using physical methods because the substances are not chemically combined.

Common Separation Techniques

1. Filtration

• Used for: Separating insoluble solids from liquids
• Example: Sand and water
• Method: Pour through filter paper; solid stays, liquid passes through

2. Evaporation/Crystallization

• Used for: Separating soluble solids from liquids
• Example: Salt and water
• Method: Heat to evaporate water, leaving solid behind

3. Distillation

• Used for: Separating liquids with different boiling points
• Example: Water and ethanol
• Method: Heat mixture; liquid with lower boiling point evaporates first, condenses separately

4. Fractional Distillation

• Used for: Separating liquids with similar boiling points
• Example: Crude oil separation
• Method: Uses fractionating column to separate based on boiling points

5. Chromatography

• Used for: Separating mixtures of dissolved substances
• Example: Separating dyes in ink
• Method: Different substances travel at different rates through a medium

6. Magnetic Separation

• Used for: Separating magnetic materials
• Example: Iron filings from sand
• Method: Use magnet to attract magnetic material

7. Decanting

• Used for: Separating liquids from solids that have settled
• Example: Water from sediment
• Method: Pour off the liquid, leaving solid behind

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Separating Compounds

Compounds cannot be separated by physical methods - they require chemical reactions.

Examples

Electrolysis:

• Water (H₂O) → Hydrogen (H₂) + Oxygen (O₂)
• Requires electricity to break chemical bonds

Thermal Decomposition:

• Copper carbonate (CuCO₃) → Copper oxide (CuO) + Carbon dioxide (CO₂)
• Requires heat to break down the compound

Reaction with Acids:

• Some compounds can be broken down by reacting with acids

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Step-by-Step Method for Classification Problems

1. Identify the composition - One type of atom or different types?
2. Check if chemically combined - Can it be separated physically?
3. Determine composition - Fixed or variable?
4. Identify properties - Same as components or different?
5. Classify - Element, compound, or mixture
6. Verify - Does it fit all characteristics?

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Worked Examples

Example 1: Classifying Substances

Classify each of the following: (a) Iron (b) Iron sulfide (c) Iron and sulfur mixed together

Solution: (a) Iron (Fe): Element - made of only iron atoms, cannot be broken down (b) Iron sulfide (FeS): Compound - iron and sulfur chemically combined, fixed composition (c) Iron and sulfur mixture: Mixture - physically mixed, can be separated with a magnet, variable composition

Example 2: Explaining Properties

Why does water have different properties from hydrogen and oxygen?

Solution:

• Water is a compound formed when hydrogen and oxygen chemically combine
• During chemical combination, atoms rearrange and form new chemical bonds
• This creates a new substance (water) with completely different properties
• Hydrogen is a gas that burns; oxygen supports burning; water puts out fires
• The properties change because a new substance is formed with different structure and bonding

Example 3: Separation Methods

Suggest how to separate a mixture of salt, sand, and water.

Solution:

1. Filtration: Pour mixture through filter paper to separate sand (insoluble solid)
2. Evaporation: Heat the salt solution to evaporate water, leaving salt crystals behind

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Common Examiner Traps (and How to Dodge Them)

• Confusing compounds with mixtures - Compounds are chemically combined; mixtures are physically mixed
• Thinking mixtures have formulas - Only compounds have chemical formulas
• Forgetting compounds have fixed composition - Mixtures have variable composition
• Not understanding separation methods - Physical methods for mixtures; chemical methods for compounds
• Confusing properties - Compounds have different properties; mixtures retain component properties
• Elements vs compounds - Elements cannot be broken down; compounds can be

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IGCSE Elements, Compounds and Mixtures Practice Questions

Question 1: Classification

State whether each is an element, compound, or mixture: a) Copper b) Copper sulfate c) Copper and zinc mixed together

Solution: a) Element - Pure copper, one type of atom b) Compound - Copper and sulfur chemically combined c) Mixture - Two elements physically mixed

Question 2: Properties

Explain why a compound has different properties from the elements that form it.

Solution:

• During compound formation, elements chemically combine
• Atoms rearrange and form new chemical bonds
• This creates a completely new substance with different structure
• The new structure gives different properties
• Example: Sodium (reactive metal) + Chlorine (poisonous gas) → Salt (safe to eat)

Question 3: Separation

Describe how you would separate a mixture of sand and salt.

Solution:

1. Add water to dissolve the salt (sand is insoluble)
2. Filter to separate sand (residue) from salt solution (filtrate)
3. Evaporate the salt solution to obtain salt crystals

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Frequently Asked Questions About IGCSE Elements, Compounds and Mixtures

What is an element?

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

What is a compound?

A compound is a pure substance made of two or more different elements chemically combined in fixed proportions. It has properties different from its component elements.

What is a mixture?

A mixture contains two or more different substances that are physically mixed, not chemically combined. It can be separated by physical methods.

How can you tell the difference between a compound and a mixture?

Compound: Fixed composition, different properties from components, separated by chemical methods, has a chemical formula. Mixture: Variable composition, properties of components retained, separated by physical methods, no formula.

Can mixtures be separated?

Yes, mixtures can be separated by physical methods such as filtration, evaporation, distillation, chromatography, etc., because substances are not chemically combined.

Can compounds be separated by physical methods?

No, compounds require chemical reactions to be separated because the elements are chemically bonded together.

What is the difference between homogeneous and heterogeneous mixtures?

Homogeneous mixtures have uniform composition (looks the same throughout, like solutions). Heterogeneous mixtures have non-uniform composition (can see different parts, like sand and water).

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Related IGCSE Chemistry Resources

Strengthen your IGCSE Chemistry preparation with these comprehensive guides:

• IGCSE Atomic Structure and the Periodic Table: Complete Guide - Master atomic structure and periodic trends
• IGCSE Diffusion: Complete Guide - Master diffusion and particle movement
• IGCSE Chemistry Revision Notes, Syllabus and Preparation Tips - Complete syllabus overview, topic breakdown, and revision strategies
• IGCSE Past Papers Guide - Access free IGCSE past papers and exam resources

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