Resources · 7 min read
Where VCE Chemistry marks are lost — straight from examiner reports
The recurring ways VCE Chemistry students drop marks — collision-theory wording, equilibrium explanations that stop short, states and ΔH signs, electrode polarity, spectra — with real VCAA examiner-report notes and a pre-submit checklist.
In Chemistry, the difference between a 40 and a 45 is often precision of wording, not depth of knowledge. The VCAA examiner reports (2022–2025) call out the same recurring losses every year. Here are the big ones, with what the reports actually say.
1. Collision-theory answers without 'per unit time'
Rate explanations have to reference successful collisions AND time. The 2022 report is blunt: students "must always refer to the number of successful collisions per unit time … Without this reference to time, no mark can be allocated." Name both the proportion of successful collisions and the frequency per unit time.
2. Equilibrium explanations that stop short
A shift isn't the full answer — you need the consequence. On a 2025 equilibrium question, mark 1 was identifying the reverse (exothermic) shift and mark 2 was relating it to the decreased yield. State the direction of the shift and what it does to yield/rate/concentration.
3. Thermochemical equations: states, sign and balancing
- •Include the correct states — ΔH values "had to be accompanied by the correct states."
- •Get the sign of ΔH right (exothermic negative) and make sure the equation is balanced.
- •A 2025 slip: writing the energy released as "−454 kJ" when the sign/context called for the opposite.
4. Electrode polarity doesn't 'swap' on recharge
A recurring misconception: "the polarity of the physical electrodes does not change … the process at that electrode changes." When a cell recharges, describe the change in process at each electrode, not a change in polarity.
5. Using what spectra DON'T show
- •An absence is evidence: no broad O–H peak rules out an acid and points to an ester.
- •Don't over-rely on exact chemical shifts — the reports note shift values are "not reliable" for pinning a structure; use them as support, not proof.
6. Precision: command words, units, data book
- •Don't just restate the stem — marks "were not awarded for only stating that enzymes catalyse or speed up reactions."
- •Missing or wrong units cost the answer mark; report the right significant figures.
- •Convert using the value provided — the m³→L conversion "was given in Item 4 of the Databook." Use the data book rather than a remembered number.
A 30-second check before you move on
- •Rate answer: successful collisions AND per unit time?
- •Equilibrium/explain: stated the shift AND its effect on yield/rate?
- •Thermochemical: states, correct ΔH sign, balanced?
- •Units, significant figures, and data-book conversions all correct?
- •Answered the command word — and added knowledge beyond the stem?
The quickest way to stop leaking these marks is to be marked the way the exam is — mark by mark, told exactly which step was missing. That's what ATAR99 does on written Chemistry answers.