IB DP Physics · Exam special · SL & HL · marking points, ECF, OWTTE and what examiners look for · ~7 min read
IB Physics Command Terms and How Markschemes Award Marks
What every IB Physics command term asks for, and how Paper 2 markschemes award marks: marking points, "max" totals, alternative answers, essential words, OWTTE, error carried forward and the rules on units and significant figures.
Command termsMarking points"max" totalsAlternatives & essential wordsOWTTEError carried forwardUnits & s.f.Answering to the markscheme
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No tag = SL and HLHL ONLY HL students onlyDATA BOOKLET given in the examM1A1 how marks are awardedhighlight = comes up again and againHANDY worth memorisingTest yourself at the end
In 30 seconds
- Physics markschemes award one mark per correct point. Each point is a separate idea or step (a "marking point"), so a 3-mark answer needs three distinct, correct things.
- The command term sets the type of point. "State" wants a fact, "explain" wants a cause, "determine" wants a calculated value with working.
- Knowing how the markscheme is written shows you how to write: short, precise statements in the right order, with the key physics words.
By the end you can
- Know what each command term asks for in Physics.
- Understand marking points, alternatives, OWTTE and ECF.
- Write answers that match how marks are awarded.
1Command terms in Physics
Objective 1 and 2 terms
| Command term | What it asks for | Typical marks |
|---|---|---|
| State | A name, value or brief fact; no explanation | 1 |
| Identify | Pick out the answer from options or from data | 1 |
| Label | Add names to a diagram | 1 |
| Define | The precise meaning of a term (often a ratio or a law) | 1–2 |
| Draw | A labelled, accurate diagram or line on a graph | 1–3 |
| Outline | A brief account or summary | 2 |
| Describe | A detailed account of what happens or what you see | 2–3 |
| Calculate | A numerical answer with the working | 2–3 |
| Estimate | An approximate value (order of magnitude is often enough) | 1–2 |
| Sketch | A graph showing the trend and key features, axes labelled | 2–3 |
Objective 3 terms
| Command term | What it asks for | Typical marks |
|---|---|---|
| Explain | Causes and reasons: link the physics to the effect | 2–4 |
| Determine | A value from data, a graph or several steps | 2–4 |
| Deduce | A conclusion that follows from the information given | 2–3 |
| Show that | Every step to a given value, ending with one more s.f. | 2–3 |
| Suggest | A plausible answer using physics (more than one may be right) | 1–2 |
| Discuss | Several arguments or factors, with a balanced conclusion | 3–4 |
| Evaluate | Strengths and limitations, and a judgement | 3–4 |
| Predict | An expected result, with a reason | 1–2 |
| Compare | Similarities and differences, both mentioned | 2 |
Exam tipDefine is strict: learn definitions word for word in meaning. "Specific heat capacity: the energy needed to raise the temperature of 1 kg of a substance by 1 K."
2How a Physics markscheme is written
- Ticks: each marking point ends with a tick (✓). One tick = one mark.
- "max": sometimes there are more marking points than marks, written as e.g. "3 max". Any three correct points score full marks.
- Order: points can usually be made in any order, unless the notes say otherwise.
- Slash ( / ): alternative wording; either is accepted ("speed / velocity").
- OR: an alternative answer or method.
- Angled brackets « »: words that are helpful but not needed for the mark.
- Underlined words: essential. Without that exact idea, the point doesn't score.
- OWTTE ("or words to that effect"): the meaning matters, not the exact words. Clear communication beats perfect grammar.
- ALTERNATIVE 1 / 2: different valid approaches, each fully marked.
Error carried forward (ECF)
- If you get a wrong value in one part and use it correctly later, the later marks can still be awarded. The markscheme says "Allow ECF".
- ECF only works if your working is visible. A bare number can't be followed.
- The first error is still penalised, so check key values (a converted temperature, a calculated radius) before moving on.
Units and significant figures
- Usually not penalised in Paper 2 unless the notes say so, for example when the question asks for units or a stated precision.
- But the answer must be the right size. Forgetting to convert cm to m gives a wrong value, and that loses the answer mark.
- Don't rely on leniency: give units and 2–3 significant figures every time; some questions do test them.
3Writing to the markscheme
Worked example
Explain why a satellite in a circular orbit at constant speed is accelerating. [2]
- The direction of the velocity is continuously changing, so the velocity changes ✓
- acceleration is the rate of change of velocity, caused by the gravitational force towards the centre of the orbit (centripetal) ✓
Worked example
State what is meant by two sources being coherent. [1]
- They have a constant phase difference ✓ ("same frequency" alone doesn't score; "constant phase difference" is the essential idea)
Worked example
A gas is heated at constant volume. Explain why its pressure increases. [3]
- The mean kinetic energy of the molecules increases with temperature, so they move faster ✓
- they collide with the walls more often ✓
- and with greater change in momentum per collision, so the force per unit area increases ✓
- One idea per sentence. It is easier for the examiner to tick, and easier for you to count.
- Use the key word the markscheme will look for: "constant phase difference", "rate of change of flux", "resultant force", "mean kinetic energy".
- Don't repeat the question. If the stem says "the temperature is constant", that sentence earns nothing in your answer; reports note that restating the stem scores zero.
- Don't contradict yourself. A correct point followed by a wrong one can cancel the mark.
Common mistakeWriting a long paragraph for a 2-mark "explain". Two clear points earn the marks; extra sentences only add the risk of a contradiction.
4Calculation marks
- The first mark is often for a step ("conversion of T to 310 K seen", "use of F = ma"), the last for the value.
- Range answers: for graph readings, markschemes accept a range of values (e.g. 480–560 m). Show your gradient triangle or area so the examiner can follow it.
- "Show that" values: if you can't get the given value, use it in the next part; the follow-on marks are still available.
Linking questionPut this into practice with Paper 2 answers, Paper 1B data skills and the data booklet guide.
Test yourself — cover the answers first
Quick check
- What does "3 max" mean in a markscheme?
- What do words in « » mean?
- What does OWTTE mean?
- What is ECF?
- Define coherent sources.
Show answers
- there are more marking points than marks; any three correct ones score full marks
- they are not needed for the mark
- or words to that effect: the meaning is what counts
- error carried forward: a wrong earlier value used correctly still earns later marks
- sources with a constant phase difference
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