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Chemistry Revision

Atoms, reactions & the periodic table — part of Science on KODO.

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Chemistry is a core area of KS3 Science in the national curriculum. It covers essential concepts that build the foundation for GCSE study and beyond.

This topic includes subtopics such as Atoms, elements and compounds, States of matter and particle model, Acids and alkalis (pH), Chemical reactions and more. Each area is tested with multiple-choice questions that include detailed explanations to deepen your understanding.

Quick Reference

pH < 7Acidic
pH = 7Neutral
pH > 7Alkaline
First 10 elementsH, He, Li, Be, B, C, N, O, F, Ne

Key Definitions

Element
A substance made of only one type of atom. Listed on the periodic table.
Compound
A substance made of two or more different elements chemically bonded together.
Mixture
Two or more substances not chemically bonded — can be separated by physical methods.
Atom
The smallest particle of an element that retains its chemical properties.
pH scale
Measures acidity/alkalinity from 0 (strong acid) to 14 (strong alkali). 7 is neutral.

What You'll Cover

Atoms, elements and compounds
States of matter and particle model
Acids and alkalis (pH)
Chemical reactions
The Periodic Table
Periodic table
Acids, alkalis and pH
States of matter

Test Yourself — Chemistry

Try 3 quick questions. No account needed.

Quick Quiz

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Memory Tricks & Mnemonics

"OIL RIG" — Oxidation Is Loss, Reduction Is Gain (of electrons)

Remember redox reactions.

"Acid + Metal → Salt + Hydrogen"

Key reaction equation pattern.

"Acid + Alkali → Salt + Water" (neutralisation)

The most common reaction type in KS3 Chemistry.

Frequently Asked Questions

What is Element in Science?+
A substance made of only one type of atom. Listed on the periodic table.
What is Compound in Science?+
A substance made of two or more different elements chemically bonded together.
What is Mixture in Science?+
Two or more substances not chemically bonded — can be separated by physical methods.
What is Atom in Science?+
The smallest particle of an element that retains its chemical properties.
What does Chemistry cover in KS3 Science?+
Chemistry in KS3 Science covers Atoms, elements and compounds, States of matter and particle model, Acids and alkalis (pH), Chemical reactions, The Periodic Table, Periodic table, Acids, alkalis and pH, States of matter. Atoms, reactions & the periodic table.
What is the best way to revise Chemistry?+
Test yourself rather than re-reading notes. Do a short Chemistry quiz, read the explanation for every answer you get wrong, then come back to those questions a few days later. KODO does this automatically with spaced repetition, and you can turn any topic into printable flash cards.
Is Chemistry revision on KODO free?+
Yes. KODO is free for everyone until Friday 18 December 2026, with unlimited quizzes on Chemistry and every other topic. After that there is still a free plan with daily quizzes.

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