GCSE Chemistry: Chemical Changes — Deep Revision Workbook

Inside GCSE Chemistry: Chemical Changes — Deep Revision Workbook

order metals by reactivity and use oxidation and reduction, predict metal + acid and metal + water products, extract metals by reduction with carbon, place substances on the pH scale, name salts and describe how to make a soluble salt, then work out the electrode products and half-equations in electrolysis before a full exam-style challenge. About 45 minutes.

Learning objectives

• the reactivity series, displacement and redox — oxidation and reduction defined by oxygen and by electrons (OIL RIG, higher), the order from potassium to gold, and displacement of a less reactive metal;
• reactions of metals — metal + acid → salt + hydrogen, reactive metal + water → metal hydroxide + hydrogen, and extraction of metals from their oxides by reduction with carbon (or by electrolysis for the more reactive metals);
• acids, alkalis and the pH scale — H+ and OH− ions, strong versus weak acids, neutralisation to a salt and water (plus carbon dioxide with a carbonate), naming chloride, sulfate and nitrate salts, and making a soluble salt by reaction and filtration;
• electrolysis — molten and aqueous compounds, ions moving to the anode (positive) and cathode (negative), half-equations at each electrode, and the extraction of aluminium from aluminium oxide dissolved in molten cryolite.

Activities in this book

1. Section 1 — Reactivity, Displacement & Redox

   oxidation is the gain of oxygen and reduction is the loss of oxygen; in terms of electrons, remember OIL RIG — Oxidation Is Loss, Reduction Is Gain. The reactivity series runs from potassium (most reactive) to gold (least reactive), and a more reactive metal displaces a less reactive one from its compound.

2. Section 2 — Metals with Acids & Water, and Extraction

   metal + acid makes a salt + hydrogen; a reactive metal + water makes a metal hydroxide + hydrogen. Metals less reactive than carbon can be extracted from their oxides by reduction with carbon, but metals more reactive than carbon (such as aluminium) must be extracted by electrolysis.

3. Section 3 — Acids, pH, Strong & Weak, Neutralisation & Salts

   the pH scale runs 0–14: below 7 is acidic, 7 is neutral, above 7 is alkaline. Acids release H+ (hydrogen) ions and alkalis release OH- (hydroxide) ions. A strong acid is fully ionised in water; a weak acid is only partially ionised. Neutralisation makes a salt and water (plus carbon dioxide with a carbonate), and the acid decides the salt name.

4. Section 4 — Electrolysis, Half-Equations & Aluminium

   electrolysis splits an ionic compound that is molten or dissolved. Positive ions go to the cathode (negative electrode); negative ions go to the anode (positive electrode). In solution the less reactive of hydrogen and the metal is deposited at the cathode. In half-equations, the cathode is reduction (gains electrons) and the anode is oxidation (loses electrons).

5. Section 5 — Extended Exam-Style Chemistry Challenge

   this is your 6-mark extended-answer practice. Choose one reaction from Chemical Changes and explain it in full sentences, using the correct keywords and a word or balanced symbol equation. Examiners reward a clear structure, correct science and precise vocabulary.

Suggestions for teaching

• Fix redox first. Define oxidation and reduction in terms of oxygen, then extend to electrons with OIL RIG for higher tier, applying both to extraction and electrolysis.
• Anchor everything to the reactivity series. Use one ordered list to explain displacement, reactions with acid and water, and the choice between carbon reduction and electrolysis.
• Drill the general equations. Rehearse metal + acid → salt + hydrogen, acid + alkali → salt + water and acid + carbonate → salt + water + carbon dioxide until automatic.
• Name salts by the acid. Hydrochloric → chlorides, sulfuric → sulfates, nitric → nitrates — then practise full names such as potassium sulfate, and the make-a-salt method by filtration and crystallisation.
• Make electrolysis physical. Link positive ions to the cathode and negative ions to the anode, write half-equations, and use aluminium oxide in cryolite as the worked example.