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A free course

Chemical Changes

Six short lessons build up how to recognise, describe and predict a chemical change — each with its own live simulation. Then a rusting investigation and ten practice questions tie it all together.

How this works

Go in order the first time — each lesson leans on the one before it. Every lesson has something to click, drag, or mix, so you're never just reading. Budget about 10 minutes a lesson.

Lesson 1

Physical vs chemical change

The one question that decides everything: has a new substance formed?

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Lesson 2

Atoms and conservation of mass

Why nothing is created or destroyed, and how to write a word equation.

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Lesson 3

Types of chemical change

Combustion, thermal decomposition, oxidation — and what rusting actually needs.

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Lesson 4

Acids, alkalis and indicators

The pH scale, and how litmus and Universal Indicator reveal it.

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Lesson 5

Neutralisation and acid reactions

Acid + alkali, acid + metal, acid + carbonate — three reactions, three tests.

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Lesson 6

Chemical changes in daily life

The same reactions, helping us or costing us — it depends on context.

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The lab

Does rust need water and air?

The classic Sec 2 investigation, live: three reference tubes plus one you control.

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Practice

20 questions

From classifying a change up to word equations and the rusting investigation. Self-checking.

Practice →