Tutes4U Editorial Team
Educational guide · Based on linked official examination specifications
A student can remember every step of a titration but still find the exam question difficult. The question may ask why the flask was rinsed a particular way, which result is anomalous or what changes would improve confidence in the outcome. That is scientific reasoning, not simple recall.
This guide focuses on AQA Chemistry 7405. Other exam boards have their own practical activity lists and assessment requirements. Practical work must be carried out and assessed through the school or centre; private online tutoring does not replace that requirement.
Expect questions about why a method works, not only what happened in the lab. This guide provides concrete practice you can use today and official sources to check your specification.
What examiners can assess about a practical
Expect questions about why a method works, not only what happened in the lab.
The official AQA required activities include titration, measuring enthalpy change, rates investigations, qualitative inorganic tests, organic analysis, electrochemical cells, pH changes, organic preparation and chromatography. You don't need to learn them as twelve isolated stories. Group them by skills: measurement, controlling variables, processing data, identifying substances and evaluating results.
The teacher-assessed practical endorsement is separate from the A-Level written grade. However, AQA's written papers assess practical knowledge and skills, so the underlying methods still matter for examination preparation.
| Exam request | What a complete response should address |
|---|---|
| Explain a method step | Purpose, effect on accuracy/validity and what might happen otherwise |
| Process measurements | Correct calculation, units, significant figures and any appropriate graph |
| Identify an error | Specific issue, direction of effect where possible and why |
| Suggest an improvement | Realistic change linked to the particular source of uncertainty |
Worked titration example: show your chemistry and your units
Do the balanced-equation and unit conversion steps before dividing volumes.
Now ask a second question: how would a small volume reading error change the calculated concentration? A strong answer identifies which measurement was wrong, whether it was too high or low, and how that would affect the final value. Saying only ‘human error’ adds almost no useful information.
Original practice question — 1:1 neutralisation
20.0 cm³ of 0.100 mol dm⁻³ hydrochloric acid exactly neutralises 25.0 cm³ sodium hydroxide solution. For HCl + NaOH → NaCl + H₂O, calculate the concentration of sodium hydroxide.
Show the worked approach
Moles of HCl = 0.100 × (20.0 ÷ 1000) = 0.00200 mol. The equation is 1:1, so NaOH also has 0.00200 mol. Volume of NaOH = 25.0 ÷ 1000 = 0.0250 dm³. Concentration = 0.00200 ÷ 0.0250 = 0.0800 mol dm⁻³. Always show the conversion from cm³ to dm³ and check the mole ratio.
Separate accuracy, precision and uncertainty
Vague language is a common obstacle in practical-data questions.
Precision concerns the spread or repeatability of measurements. Accuracy concerns closeness to the accepted or true value. Uncertainty communicates the range of values consistent with the measuring process. These ideas interact but should not be used as synonyms.
For a simple percentage uncertainty calculation, divide the absolute uncertainty by the measured quantity and multiply by 100. For example, ±0.05 cm³ on a 25.00 cm³ volume corresponds to 0.20% for that one stated measurement (0.05 ÷ 25.00 × 100). Actual experiments may require combining reading uncertainties: follow the wording of the question and the guidance for the equipment used.
- Quote the actual apparatus and its stated resolution or uncertainty.
- Explain whether a suggested change reduces random scatter or a systematic bias.
- Check whether repeats are close together before deciding which values to average.
- Record units for every value and use a suitable number of significant figures.
Make method-evaluation answers specific
A useful improvement must address a named weakness.
An example of an unhelpful response is ‘use better equipment’. A useful response names the instrument or step and explains the difference it makes. For instance, using a pipette to transfer an exact fixed volume can be more reliable than estimating that volume with a measuring cylinder, provided the method calls for a fixed volume.
For rate experiments, ask whether temperature, concentration, surface area and apparatus setup were controlled. For chromatography, explain the relationship between the solvent front, distance travelled and the value being calculated. For enthalpy measurements, distinguish heat exchange with surroundings from poor arithmetic.
| Weak answer | Improved explanation |
|---|---|
| ‘The experiment was wrong.’ | ‘Heat was lost to the surroundings, so the measured temperature change may underestimate the actual change.’ |
| ‘More repeats.’ | ‘Repeat the titre until results are concordant, then calculate a mean from the consistent readings.’ |
| ‘Measure properly.’ | ‘Read the burette at eye level to reduce parallax error.’ |
A practical-exam revision checklist
Turn each required activity into five answerable questions.
Practice with an official question, mark your response and rewrite any vague explanation with the precise chemical reason. Keep a short list of recurring mistakes; take that list to a tutor if you need targeted feedback.
- Can I explain the purpose of the main apparatus and procedure?
- Can I identify the independent, dependent and controlled variables?
- Can I process a set of data accurately, with units and any uncertainty?
- Can I justify an improvement with a clear scientific reason?
- Can I link the experiment's outcome to the relevant theory?
Common questions
Are AQA A-Level Chemistry required practicals examined in written papers?+
Yes. The written assessment covers knowledge and skills associated with practical work as well as theory. The practical endorsement is separately assessed by the school or centre.
Can online tutoring replace the required practicals?+
No. Tutoring can support explanation, calculations and exam practice, but it does not replace hands-on practical work or teacher-assessed endorsement requirements.
Do all exam boards use AQA's twelve-practical list?+
No. Check your specific exam board. This article describes AQA 7405 requirements and uses them as a revision example.
Official specifications and sources
Checked 17 October 2026. Exam specifications and question wording can change; always confirm the student's exam board and sitting year. Practice examples above are original teaching examples, not official past-paper questions.