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✦ Class 8 · Science
Nature of Matter: Elements, Compounds and Mixtures
You'll discover why a magnet pulls iron filings but not a black powder that looks the same.
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What this lesson covers
Step by step, in this order.
- 1Mystery: why does a magnet pick iron but not iron sulfide?
- 2Pure substance contains only one kind of particle throughout.
- 3Element: simplest form, cannot be broken into simpler substances.
- 4Compound: two or more elements chemically combined in fixed ratio, new properties.
- 5Mixture: substances combined without chemical change. Uniform examples: air, salt water. Non‑uniform: muddy water, sand‑salt mix.
- 6Story: Ancient Indian metalworkers discovered brass, an alloy of copper and zinc, by mixing metals.
- 7Experiment: Iron filings mixed with sulphur powder. Magnet attracts iron, not iron sulfide.
- 8TRY IT: Separate sand and salt. 1) Mix sand + salt + water. 2) Filter. 3) Evaporate filtrate. Predict what remains.
- 9Formula: density = mass / volume (kg / m³). Example: 200 g of sand occupies 0.08 m³.
- 10Separation methods: hand‑picking, sieving, filtration, evaporation, magnetic separation, decantation.
How it looks
A real board, not a video.
This board is from a different Science lesson — yours will look like this. She writes and draws while she explains, and stops to check you followed.
Doubts this lesson clears up
- Why does a magnet attract iron but not iron sulfide?
- How can water be a compound if it contains hydrogen and oxygen?
- What makes a mixture uniform or non‑uniform?
- How do we separate sand from salt using water?
- Why does some mixture float while another sinks?
- Is brass a pure substance or a mixture?
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