Chemical Reactions

Worked examples (12)extended set

• 1Spot the physical change (multiple choice)
• 2Reading particle diagrams
• 3Naming changes of state and dissolving
• 4What a heating curve shows
• 5Classifying changes from observations
• 6Heating hydrated copper(II) sulfate
• 7Using masses as evidence of a new substance
• 8Which change breaks bonds inside molecules? (multiple choice)
• 9From crude oil to a plastic bottle
• 10Iron and sulfur: mixture or compound?
• 11What happens when a candle burns?
• 12Testing three 'rules' for spotting a chemical change

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style

Worked examples (12)extended set

• 1Describing how five changes affect the rate
• 2Reading a gas syringe graph and finding a mean rate
• 3Collision theory for a more concentrated acid (multiple choice)
• 4Explaining the effect of cooling and of lowering the pressure
• 5A catalyst on a reaction pathway diagram
• 6Powder versus lumps: a mass-loss experiment
• 7Stop-watch readings and relative rate at three temperatures
• 8Evaluating gas collection over water
• 9Why the colder reaction is slower (multiple choice)
• 10Predicting new curves using moles
• 11Showing a catalyst is unchanged and using its results
• 12Finding a pattern and an anomaly in rate data

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 6 (Alternative to Practical) / Paper 4 style

Worked examples (12)extended set

• 1Heating pink crystals and testing the liquid
• 2Reading an equilibrium equation
• 3When is equilibrium reached? Reading concentration–time graphs
• 4Conditions for the highest yield (multiple choice)
• 5Completing a table: yield and rate
• 6The Haber process: sources, equation and conditions
• 7The Contact process: making sulfur trioxide
• 8Why the Haber process runs at 450 °C (multiple choice)
• 9Deducing ∆H and moles of gas from a yield graph
• 10Sketching the effect of a catalyst and of heating
• 11Choosing conditions for an endothermic equilibrium
• 12Adding alkali, acid and silver ions to bromine water

Model answers (6)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style

Worked examples (12)extended set

• 1Reducing copper(II) oxide with hydrogen
• 2Naming compounds with Roman numerals
• 3Oxidation numbers in compounds and ions
• 4Is it redox? Using oxidation numbers
• 5Oxidising agent and reducing agent (multiple choice)
• 6Halogen displacement: results, ionic equation and electrons
• 7Identifying oxidising and reducing agents by colour changes
• 8Extracting vanadium with aluminium
• 9Iron(III) ions oxidising iodide ions
• 10Redox in a catalytic converter
• 11Following sulfur through a reaction scheme
• 12One element oxidised and reduced (multiple choice)

Model answers (5)

• ✓Model answer — Paper 4 short-answer style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 structured style
• ✓Model answer — Paper 4 (Extended) structured style
• ✓Model answer — Paper 4 (Extended) structured style