How Marks Are Awarded in IB Physics Exams

The IB Marking Philosophy

IB Physics exams are marked using a positive marking approach. This means examiners look for reasons to give you marks, not take them away. Understanding this philosophy changes how you should write your answers.

Every mark in the mark scheme falls into one of these categories:

The Four Types of Marks

1. A-marks (Answer marks)

These are awarded for the correct final answer with correct units. In a 3-mark calculation:

• If you get the right answer with no working: you typically get 1/3 (just the A-mark)
• If you get the wrong answer but show correct method: you can still get 2/3

Lesson: Never skip working, even if you can do it mentally.

2. M-marks (Method marks)

Awarded for using the correct equation or correct approach, even if the final answer is wrong. Method marks are “follow-through” — meaning if you make an arithmetic error in step 1 but apply the correct method in step 2 using your wrong value, you still get the M-mark.

Example:

• Question: Calculate the kinetic energy of a 2 kg object moving at 5 m/s.
• Student writes: Ek = ½mv² = ½(2)(5) = 5 J ✗ (arithmetic error: should be 25)
• Marks awarded: M1 (correct equation) + M1 (correct substitution) = 2/3 marks

This is called Error Carried Forward (ECF), and it’s one of the most important concepts in IB marking.

3. C-marks (Communication marks)

Awarded for:

• Stating the correct units
• Using appropriate significant figures
• Labelling graphs correctly
• Writing clear, logical explanations

C-marks are often the difference between a 5 and a 6, or a 6 and a 7.

4. P-marks (Process marks)

Used primarily in experimental and data analysis questions. Awarded for:

• Correct graph construction
• Appropriate use of error bars
• Correct uncertainty propagation
• Valid experimental evaluation

How “Explain” Questions Are Marked

Explanation questions use a point-based marking system. Each valid physics point earns 1 mark, up to the maximum. The mark scheme lists acceptable points, and you need to hit enough of them.

For a 3-mark “Explain” question, the mark scheme might list 5 possible marking points. You only need 3, but you must be specific:

Strategy: Write 4–5 concise points to ensure you hit at least 3.

Grade Boundaries and What They Mean

IB Physics grade boundaries vary each exam session, but typical ranges are:

Key insight: You don’t need a perfect paper to get a 7. Knowing where marks are easy to collect (units, graph labels, equation statements) can push you across a boundary.

Maximising Your Mark Total

The “Free Marks” Checklist

These marks require minimal physics knowledge but are frequently dropped:

1. Write units on every final answer — 1 mark each time
2. Label both axes on every graph with quantity and unit — 1 mark
3. State the equation before substituting — 1 mark per calculation
4. Draw a line of best fit (not dot-to-dot) — 1 mark
5. Include a direction when stating vector quantities — often 1 mark

The ECF Strategy

If you get a wrong answer in part (a) but need to use it in part (b):

• Use your wrong answer — the examiner will apply ECF and you can still get full marks for part (b)
• Never leave part (b) blank because you think part (a) is wrong

The “BOD” Rule

BOD = Benefit of the Doubt. If your answer is ambiguous but could be interpreted as correct, examiners are instructed to give you the mark. This means:

• Write clearly and legibly
• Avoid crossing out work unless you’re sure it’s wrong
• If you write two answers, the examiner marks the worse one — so cross out anything you don’t want marked

What Examiners Notice

From official IB examiner reports:

“Candidates who consistently earn high marks share one trait: they communicate their physics clearly. They don’t assume the examiner will ‘fill in the gaps.’”

“The most common reason for not awarding a mark is not a lack of knowledge — it’s a lack of specificity. ‘The force increases’ is not the same as ‘The gravitational force increases because the distance between the masses decreases.’”