Edexcel GCSE Combined Science CC3 and CC4 Chemical changes and extracting metals: a complete overview of acids, electrolysis, the reactivity series and metal extraction

What CC3 and CC4 actually demand

Chemical changes and extracting metals are reliable sources of Chemistry Paper 1 marks. The examiners reward the four acid-reaction patterns, the salt-preparation core practical, confident electrolysis predictions, and the link between the reactivity series and how a metal is extracted.

This guide walks through both topics and ties together the matching dot-point pages, each with its own practice questions.

Acids, salts and electrolysis

Acids release hydrogen ions ($H^+$, pH below 7); alkalis release hydroxide ions ($OH^-$, pH above 7). Neutralisation is $H^+ + OH^- \rightarrow H_2O$. Acids react with metals (salt + hydrogen), bases (salt + water) and carbonates (salt + water + carbon dioxide). A soluble salt is made with excess base, then filtering and crystallising.

Electrolysis breaks down molten or dissolved ionic compounds: positive ions to the cathode (reduction), negative ions to the anode (oxidation).

The reactivity series and extraction

The reactivity series ranks metals; a more reactive metal displaces a less reactive one. Oxidation is loss of electrons, reduction is gain (OIL RIG). Extraction depends on reactivity relative to carbon:

• Below carbon (iron, zinc, copper): extract by reduction with carbon.
• Above carbon (aluminium and above): extract by electrolysis.

How CC3 and CC4 are examined

• Reaction patterns. Writing the products of acids with metals, bases and carbonates.
• Core practical. Describing how to make a pure dry soluble salt with excess base.
• Electrolysis. Predicting products at each electrode and explaining in terms of ions.
• Extraction. Linking a metal's reactivity to its extraction method.

Check your knowledge

A mix of recall and application questions covering CC3 and CC4. Attempt them under timed conditions, then check against the solutions.

1. State the ion that acids produce in solution. (1 mark)
2. Write the ionic equation for neutralisation. (1 mark)
3. What are the products of an acid reacting with a carbonate? (2 marks)
4. At which electrode do positive ions gain electrons? (1 mark)
5. Define oxidation in terms of electrons. (1 mark)
6. Which metal displaces the other: a more reactive or a less reactive one? (1 mark)
7. How is iron extracted from iron oxide? (1 mark)
8. Why is aluminium extracted by electrolysis? (1 mark)