Chapter 3 · ICSE Class 8 Chemistry (Selina Concise)

Elements, Compounds and Mixtures

Review and deepen your classification of elements, compounds, and mixtures, with focus on separation techniques.

🧪 Chapter 3

Examples of an element, a compound, and a mixture Iron as an example of an element, water as an example of a compound, and sand mixed with salt as an example of a mixture Element Iron (Fe) Compound Water (H₂O) Mixture Sand + Salt
3.1

Classifying Substances

Elements have only one type of atom. Compounds have atoms of different elements chemically bonded. Mixtures have substances physically combined, not chemically bonded.

1

Is brass (a mixture of copper and zinc) an element, compound, or mixture?

A mixture (specifically an alloy), since copper and zinc are physically combined, not chemically bonded

2

Is carbon dioxide an element, compound, or mixture?

A compound

3.2

Separation Techniques

Different mixtures require different separation techniques: distillation for miscible liquids, chromatography for dyes, and sublimation for substances like naphthalene.

1

What technique would separate salt water into pure water and salt?

Distillation (or simple evaporation for the salt)

2

What technique separates the different colored dyes in ink?

Chromatography

Practice

Exercises

1. Is steel (a mixture of iron and carbon) an element, compound, or mixture?

2. What technique separates a mixture of two miscible liquids with different boiling points?

3. What technique separates dyes based on how they travel through a material?

4. Is sugar solution an element, compound, or mixture?

5. Why can mixtures be separated by physical means, but compounds cannot?

Next chapter — Atomic Structure ⚛️ →