Required Practicals
What gets examined & how. The 8 RPs, what AQA tests every time, and the framework that turns guaranteed practical marks into actual marks.
SPEC 8462 • EXAM FOUNDATIONS
~30 Marks Are Waiting
AQA states that at least 15% of overall marks across both papers come from questions on practical work. That's roughly 30 marks out of 200 — three to four whole grade boundaries.
8
Required Practicals
15%
Min Marks On Practicals
~30
Marks Per Series
Why This Lesson
Every individual RP gets its own lesson later. This lesson is the framework — the variables, terms, and exam-question types that recur across every single RP. Master it once, apply it eight times.
The 8 Required Practicals
Memorise all 8 by name and number. Two are Chemistry-only (RP2 and RP7) — Combined Science students don't sit them. Each has its own dedicated lesson later in the course.
RP1
Preparation of a soluble salt
Spec 8.2.1 → Lesson 4.04
Chem only
RP2
Titration — strong acid + strong alkali
Spec 8.2.2 → Lesson 4.06
RP3
Electrolysis of aqueous solutions
Spec 8.2.3 → Lesson 4.08
RP4
Temperature changes in reactions
Spec 8.2.4 → Lesson 5.01
RP5
Rates of reaction (gas volume + colour/turbidity)
Spec 8.2.5 → Lessons 6.01 & 6.02
RP6
Paper chromatography & R_f values
Spec 8.2.6 → Lesson 8.02
Chem only
RP7
Identification of ions in unknown compounds
Spec 8.2.7 → Lessons 8.04 & 8.05
RP8
Analysis & purification of water samples
Spec 8.2.8 → Lesson 10.02
What RP Questions Test
Across all 8 RPs, every exam question falls into one of four categories. Practise each, and you've covered the entire surface area of practical assessment.
CategoryWhat You Need to Do
1. Apparatus & methodName the specific equipment. Sequence the steps in the right order. Don't substitute generic items (e.g. "measuring cylinder" for a titration).
2. VariablesIdentify the IV, DV, and at least 3 control variables — each control with a reason .
3. Expected results & interpretationState what the data should look like; explain what the pattern shows about the chemistry.
4. Errors & improvementsIdentify random vs systematic error. Discard anomalous results. Suggest specific improvements.
The Pattern
For every RP later in this course, you'll see these same four headings. Write each RP's revision notes under these four columns — that mirrors exactly how the examiner builds the questions.
Variables — IV, DV, Controls
The single most-examined concept across all 8 RPs. Every practical question expects you to name the variables correctly.
Independent
The variable you deliberately change.
Dependent
The variable you measure in response to the IV.
Control
Anything else that could affect the DV — kept constant.
The Mark Lives In the REASON
"Keep the volume of acid the same" → 0 marks for the reason.
"Keep the volume of acid the same so that any change in rate is due only to the concentration, not the volume" → full mark.
Every control variable needs a "so that…" clause. The reason is the mark.
Reliability Terms
Four terms that appear word-for-word on mark schemes. If you use vague paraphrases, the mark scheme won't credit you.
Concordant Results
Repeat measurements that agree closely — for titrations, typically within 0.10 cm³ of each other. The mean is calculated from concordant results only.
Anomalous Result
A measurement that differs significantly from the trend or other repeats. Discard before calculating the mean.
Random Error
Unpredictable variation. Causes scatter around a true value. Reduced by repeating and averaging.
Systematic Error
A consistent shift (e.g. miscalibrated balance). All readings off by the same amount. Reduced by recalibrating or using better apparatus.
Worked Example — Anomalous Results
A student records 5 titration volumes (cm³): 24.90, 25.50, 24.85, 24.90, 24.85. Calculate the mean of the concordant titres.
✗ Wrong — 0 marks
Mean = (24.90 + 25.50 + 24.85 + 24.90 + 24.85) ÷ 5
= 125.00 ÷ 5
= 25.00 cm³
Arithmetic correct, but the mark is for understanding concordance — anomalous result not discarded first.
✓ Correct
Step 1: Identify anomalous: 25.50 differs from the others by > 0.10 cm³.
Step 2: Concordant set: 24.90, 24.85, 24.90, 24.85 — all within 0.10 cm³ of each other (range = 0.05).
Step 3: Mean = (24.90 + 24.85 + 24.90 + 24.85) ÷ 4
= 99.50 ÷ 4
= 24.875 cm³
EXAMINER ALERT — P2 Jun 2023 Q01.2 & P1 Jun 2022 Q08.2
P2 Jun 2023 Q01.2: "Of those who didn't [score full marks], the majority scored 4 marks by failing to discard the anomalous result."
P1 Jun 2022 Q08.2: the credited approach is "the mean of the concordant results, or the mean of the results within 0.10 cm³ ". Discard first. Calculate second.
RP4 Trap — One Word Costs The Mark
Real example of how method precision earns marks. A 6-mark question on RP4 (temperature changes in reactions) tested whether students could write a workable method.
"Although most candidates referred to the measurement of temperature, the key step in the method that was most often missing was the instruction to measure the highest temperature reached by the mixture." — AQA Examiner Report, P1 Jun 2022 Q02.1
✗ Misses Mark
"Measure the temperature of the mixture."
Vague — when? At the start? At the end? Continuously?
✓ Earns Mark
"Measure the highest temperature reached by the mixture during the reaction."
Specific. Tells the examiner you understand peak temperature ≠ continuous reading.
The Lesson
Every RP has at least one detail like this — a single qualifier that earns the mark. For RP4, the word is "highest". The lesson 5.01 will cover all of them for RP4.
RP1 Trap — Heating to Dryness Destroys Crystals
RP1 (preparation of a soluble salt) is one of the most-examined practicals. The single most common error is in the final crystallisation step.
"A few would not have made crystals because they evaporated to dryness by heating. Many students appear to believe that the acid is being evaporated off the solution, rather than water. There were infrequent references to using a water bath or an electric heater for the [evaporation]." — AQA Examiner Report, P1 Jun 2023 Q03.1
The Spec Method (8.2.1)
"Bunsen burner to heat dilute acid" (initial step — to speed up the reaction) + "water bath or electric heater" to evaporate the solution (final step). The Bunsen is for the reaction, NOT for evaporating the solution to dryness.
Why It Matters
Heating to dryness with a Bunsen destroys the crystal structure — you get a powder, not pure dry crystals. The mark-scheme method (P1 Jun 2023 Q03.1): heat the solution using a water bath or electric heater to crystallisation point, then leave the solution to crystallise.
RP2 Trap — Apparatus Precision
Real Jun 2024 Paper 1 mark scheme for a titration question. Look at the precision of what's accepted vs rejected — this is exactly how mark schemes work.
From P1 Jun 2024 Q09.3 Mark Scheme (RP2)
Required: "use a (volumetric) pipette to add the alkali"
Then any 2 from:
into a conical flask (ignore beaker)
add an indicator (allow named — but do not accept "add universal indicator")
take the initial burette reading
use a white tile (under the conical flask)
Two Things Worth Memorising
1.Universal indicator is wrong for titration — the colour change is gradual, not sharp. The mark scheme explicitly rejects it. Use a single-change indicator (commonly methyl orange or phenolphthalein in school).
2.Measuring cylinder for the alkali is wrong — pipette only. Measuring cylinders aren't precise enough for titration.
Practice Question
A student investigates how the concentration of hydrochloric acid affects the rate of reaction with magnesium ribbon (RP5).
(a) State the independent variable, dependent variable, and two control variables, each with a reason.5 MARKS
IV
Independent variable: the concentration of hydrochloric acid (mol/dm³).
DV
Dependent variable: the volume of hydrogen gas produced in a fixed time (or the time taken to produce a fixed volume of gas).
CV1
Control variable 1: volume of acid kept constant — so that the same number of acid particles is available to react each time, ensuring any change in rate is due only to concentration.
CV2
Control variable 2: mass and surface area of magnesium kept constant — so that the frequency of collisions between acid particles and the magnesium surface depends only on acid concentration, not on the available metal surface.
⚠️
Mark loss check: Without the "so that" clause, control variables score 0 — the reason is the mark. Temperature would be another valid control variable.
The Universal RP Checklist
For every RP later in this course, fill in this five-point checklist. It mirrors exactly what the examiner will test.
1. Variables
IV, DV, and at least 3 control variables — each with a "so that…" reason.
2. Apparatus
The specific named pieces — pipette (not measuring cylinder), gas syringe (not bowl of water for inverted measuring), water bath (not Bunsen) where evaporation matters.
3. Method qualifiers
The single words that win the mark: "highest temperature" (RP4), concordant titres within 0.10 cm³ (RP2), start line in pencil & above the solvent (RP6), fresh reagent (RP7).
4. Expected results
Numerical pattern + chemical explanation. "As concentration doubles, rate roughly doubles, because there are more acid particles per dm³ → increased frequency of collisions per second."
5. Errors & improvements
Random (repeat & mean) vs systematic (recalibrate). Discard anomalies before the mean. Specific improvement, not generic ("be more careful" earns 0).
Three Errors That Cost Real Marks
Patterns that appear repeatedly in examiner reports across multiple RPs. Fix these now and protect 4–6 marks per paper.
✗ Weak
"Keep the volume the same"Naming the control variable but not why.
✓ Strong
"Keep volume of acid the same so that…"Control variable + reason. Reason = mark.
✗ Weak
"Mean of all results = …"Including the anomalous result in the mean.
✓ Strong
"Anomalous result is X. Mean of concordant results = …"Identify, discard, then calculate.
✗ Weak
"The reaction stops"Vague — how do you know?
✓ Strong
"The reaction is complete — no more gas produced / solid no longer disappears"A specific observation, not an inference.
Three Things to Remember
Three habits that protect practical marks across all 8 RPs.
1. Every Control Variable Needs a "So That…"
Naming the control = half the work. The mark is for explaining why it must be controlled. Build the habit into every method answer from today.
2. Discard Anomalies BEFORE the Mean
The arithmetic mark depends on the concordance step coming first. Identify → discard → calculate. In titrations, "concordant" usually means within 0.10 cm³.
3. Name the Specific Apparatus
Pipette, not measuring cylinder. Gas syringe, not displacement of water (where the spec specifies). Water bath, not Bunsen for evaporation. The mark scheme accepts named pieces only.
Summary
The 8 Required Practicals
RP1: soluble salt prep · RP2: titration (chem only) · RP3: electrolysis · RP4: temperature change
RP5: rate (gas + colour) · RP6: paper chromatography & R_f · RP7: ion identification (chem only) · RP8: water analysis
≥15% of all paper marks come from RP-related questions — ~30 marks per series
Variables & Reliability Terms
IV = changed · DV = measured · CV = kept constant (with reason!)
Concordant = within 0.10 cm³ for titrations · Anomalous = discard before mean
Random error → repeat & mean · Systematic error → recalibrate
Four Question Categories
Apparatus & method · Variables · Expected results & interpretation · Errors & improvements
Every RP question fits one of these — practise each across all 8 practicals
Exam Tip
The single biggest pattern across examiner reports: students name the control variable but skip the reason. Every "control variable" answer must contain a "so that…" clause. That clause IS the mark.
Next: ~30 Marks Are Waiting