Topic 4: Chemical changes – GCSE AQA Higher Chemistry revision notes

What this topic covers

Topic 4: Chemical changes has 3 subtopics:

• Reactivity of metals
• Reactions of acids
• Electrolysis

Topic 4: Chemical changes lessons by subtopic

24 lessons, grouped by subtopic.

Reactivity of metals

• Metal Reactions and the Reactivity Series: Explore how different metals react with water and dilute acids, understand why metals form positive ions, and learn how to arrange metals in order of reactivity. Discover how experimental results help us determine metal reactivity patterns.
• Displacement Reactions and the Extended Reactivity Series: Learn how more reactive metals can displace less reactive metals from compounds, and discover how non-metals like hydrogen and carbon fit into the reactivity series to help predict chemical reactions.
• How metals are found and extracted: Learn about how different metals occur in nature and the basic principles of metal extraction, including why most metals need to be extracted from compounds.
• Reduction and oxidation in metal extraction: Understand reduction as the loss of oxygen and identify which substances are oxidised or reduced during metal extraction processes using carbon.
• Evaluating metal extraction processes: Interpret and evaluate specific metal extraction processes when given information about different methods and conditions.
• Understanding Oxidation and Reduction with Electrons: Learn the definitions of oxidation and reduction in terms of electron transfer, and practice identifying which species are oxidised and reduced in chemical reactions.
• Writing Ionic Equations for Displacement Reactions: Master the skill of writing ionic equations for displacement reactions and apply electron transfer concepts to understand these reactions.
• Metal Oxides and Oxidation Reactions: Learn how metals react with oxygen to form metal oxides and understand oxidation and reduction in terms of oxygen gain or loss.

Reactions of acids

• What Salts Are Produced in Neutralisation?: Learn how the acid used and the base determine which salt is produced in neutralisation reactions, and practice predicting products.
• Neutralisation Reactions and Salt Formulae: Understand the general reactions of acids with alkalis, bases and carbonates, and learn to write formulae for the salts produced.
• Making Soluble Salts from Acids: Learn how to prepare soluble salts by reacting acids with metals, metal oxides, hydroxides, or carbonates. Understand the process of adding excess solid, filtering, and obtaining salt solutions.
• Crystallising Salt Solutions and Making Pure Samples: Discover how to crystallise salt solutions to produce solid salts and develop skills to describe complete methods for making pure, dry samples of named soluble salts.
• Acid-Metal Reactions: Products and Patterns: Learn how acids react with metals to produce salts and hydrogen gas, focusing on reactions of magnesium, zinc and iron with hydrochloric and sulfuric acids.
• Redox in Acid-Metal Reactions: Understand how acid-metal reactions are redox processes involving electron transfer, and identify which species are oxidised and reduced in chemical equations.
• Understanding Acid Strength and Concentration: Distinguish between dilute/concentrated and weak/strong acids, learn about complete and partial ionisation, and identify examples of strong and weak acids.
• pH Scale and Hydrogen Ion Concentration: Explore the relationship between acid strength and pH values, understand how hydrogen ion concentration changes with pH, and learn about neutrality and relative acidity.

Electrolysis

• Understanding Electrode Reactions in Electrolysis: Learn how ions gain and lose electrons at different electrodes during electrolysis, identifying reduction at the cathode and oxidation at the anode.
• Writing Half Equations for Electrode Reactions: Master the skill of representing electrode reactions using half equations, including examples for hydrogen and oxygen formation with correct electron notation.
• Predicting Products in Aqueous Electrolysis: Learn how the reactivity of elements determines which ions are discharged during electrolysis of aqueous solutions, including the role of water molecules breaking down into hydrogen and hydroxide ions.
• Products at the Cathode and Anode: Understand when hydrogen is produced at the cathode based on metal reactivity, and when oxygen versus halogens are produced at the anode depending on the presence of halide ions.
• Electrolytic extraction of reactive metals: Learn why electrolysis is used to extract highly reactive metals, the energy requirements of the process, and the need for specific electrolyte mixtures.
• Aluminium production and electrode replacement: Explore the industrial production of aluminium through electrolysis of aluminium oxide and cryolite, and understand why positive electrodes need continuous replacement.
• Products of Electrolysis in Molten Ionic Compounds: Learn how electrolysis of molten ionic compounds produces metals at the cathode and non-metals at the anode, using lead bromide as an example, and develop skills to predict products of electrolysis for any binary ionic compound.
• Understanding Electrolytes and Ion Movement: Explore how ionic compounds become electrolytes when melted or dissolved, allowing ions to move freely and conduct electricity. Learn how electric current causes ions to migrate to opposite electrodes during electrolysis.

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