Chemical Changes | AQA GCSE Chemistry, Higher tier (8462)
Chemical Changes
- 195 questions
- 11 subtopics
- Paper 1
- Paper 1
Chemical Changes is examined in Chemistry Paper 1.
It covers the reactivity series, metal oxides, extraction, and redox in terms of electrons, acids reacting with metals, neutralisation and salts, soluble salts, the pH scale and neutralisation, titrations, strong and weak acids, the process of electrolysis, and molten ionic compounds, using electrolysis to extract metals, electrolysis of aqueous solutions and representation of reactions at electrodes as half equations.
Sample questions from Chemical Changes
Answer each one closed book first, then open the answer.
-
The reactivity series
State the rule that decides whether one metal will take another metal's place in a compound.
Show the answer
A more reactive metal displaces a less reactive metal from its compound. -
Metal oxides, extraction, and redox in terms of electrons
In what form are most metals found in the Earth, and what does this mean must be done to obtain them?
Show the answer
They are found as compounds, so a chemical reaction is needed to separate the metal from what it is joined to. -
Acids reacting with metals, neutralisation and salts
When magnesium reacts with hydrochloric acid, what happens to the hydrogen from the acid?
Show the answer
It is reduced to hydrogen gas, which bubbles out of the solution. -
Soluble salts
How is a solid salt obtained from a solution of that salt?
Show the answer
The solution is crystallised. -
The pH scale and neutralisation
What is the full range of the pH scale?
Show the answer
It runs from 0 to 14. -
Titrations
Which piece of apparatus holds the acid and lets it be added a little at a time?
Show the answer
A burette. -
Strong and weak acids
Explain why only a small fraction of the ethanoic acid molecules in a solution release hydrogen ions.
Show the answer
Ethanoic acid is a weak acid, so its ionisation is only partial and most of the molecules stay intact. -
The process of electrolysis, and molten ionic compounds
What name is given to the negative electrode?
Show the answer
The cathode.
The 11 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| The reactivity series | Metals forming positive ions and reactivity as the tendency to do so, the series from potassium to copper with hydrogen and carbon for comparison, displacement reactions, ordering metals by their reactions with water and dilute acid in a fair test, and why potassium reacts more vigorously than magnesium. | 20 |
| Metal oxides, extraction, and redox in terms of electrons | Metal oxides and oxidation and reduction in terms of oxygen, why gold is found as the metal, extracting metals less reactive than carbon by reduction with carbon, comparing extraction methods, and oxidation and reduction in terms of electrons, with ionic and half equations for displacement reactions. | 20 |
| Acids reacting with metals, neutralisation and salts | Metals reacting with dilute acids to give a salt and hydrogen, the test for hydrogen, these reactions as redox in terms of electrons, neutralisation of acids by alkalis, bases and metal carbonates, the difference between a base and an alkali, naming salts from their acids, and deducing salt formulae from their ions. | 20 |
| Soluble salts | Making a soluble salt by adding an insoluble metal, oxide, hydroxide or carbonate to an acid in excess, filtering off the unreacted solid, crystallising and drying the salt, the copper sulfate preparation, choosing gentle heating, safety precautions, and why crystals can lose mass. | 16 |
| The pH scale and neutralisation | Hydrogen ions in acids and hydroxide ions in alkalis, aqueous solutions, the pH scale from 0 to 14 measured with universal indicator or a pH probe, acidic, neutral and alkaline values, and neutralisation as hydrogen ions reacting with hydroxide ions to form water, with its ionic equation. | 18 |
| Titrations | What a titration measures and why an indicator is needed, the pipette and burette, adding acid drop by drop near the end point, concordant titres, the white tile and rinsing, working out the titre, why the first run is rough, and calculating concentrations and volumes from titration results. | 18 |
| Strong and weak acids | Strong acids as completely ionised and weak acids as partially ionised, examples of each, why a strong acid has a lower pH than a weak acid of the same concentration, the tenfold change in hydrogen ion concentration per pH unit, concentrated and dilute acids, and neutrality at pH 7. | 17 |
| The process of electrolysis, and molten ionic compounds | Electrolytes and why molten or dissolved ionic compounds conduct, electrolysis and the cathode and anode, which ions move to each electrode, what half equations show and what must balance in them, inert electrodes, and predicting the products of electrolysing molten lead bromide, sodium chloride and zinc bromide. | 16 |
| Using electrolysis to extract metals | When electrolysis is used to extract a metal, why the compound must be molten and why the process is costly, and the extraction of aluminium from aluminium oxide mixed with cryolite using carbon anodes that burn away. | 15 |
| Electrolysis of aqueous solutions | Which ions are present in a solution, how relative reactivity decides whether the metal or hydrogen forms at the cathode, when oxygen or a halogen forms at the anode, predicting products, and testing the gases collected. | 18 |
| Representation of reactions at electrodes as half equations | Why cathode reactions are reductions and anode reactions oxidations, half equations for metal ions, hydrogen ions, halide ions, oxide ions and hydroxide ions, balancing atoms and charge, and the two ways of writing an oxidation. | 17 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
-
Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
-
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
-
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
AQA GCSE Chemistry, Higher tier Active Recall Guide
Every topic, not just this one. 1,648 questions with their answers.