Mark Scheme Patterns & Common Mistakes

Understanding how AQA mark schemes work is as important as knowing the physics content. Mark schemes are rigid — examiners follow them precisely. If you know what patterns examiners look for, you can structure every answer to pick up maximum marks. This lesson covers calculation patterns, equation use, units, graph skills, common conceptual mistakes, and the specific rules for significant figures and extended responses.

---

Calculation Question Pattern

Every calculation question in AQA GCSE Physics follows a standard pattern. Examiners look for specific steps, and each step can earn a mark even if your final answer is wrong. This means showing your working can be the difference between 0 marks and 2 out of 3 marks.

The Standard Calculation Steps

Step	What to Do	Mark Awarded For
1. Write the equation	State the relevant equation (in words or symbols)	Correct equation selected
2. Substitute	Put the numbers from the question into the equation	Correct substitution
3. Rearrange (if needed)	Rearrange the equation to make the unknown the subject	Correct rearrangement
4. Calculate	Perform the arithmetic	Correct numerical answer
5. Unit	Write the correct unit	Correct unit

Worked Example

Question: A car of mass 1200 kg is travelling at 15 m/s. Calculate its kinetic energy. (3 marks)

Step	Working
Equation	E_k = 0.5 x m x v^2
Substitution	E_k = 0.5 x 1200 x 15^2
Calculation	E_k = 0.5 x 1200 x 225 = 135 000 J
Answer with unit	135 000 J (or 135 kJ)

Exam Tip: Even if you make an arithmetic mistake, you still get marks for the correct equation and correct substitution. ALWAYS show your working. Never just write a final number.

Rearranging Equations

Many exam questions require you to rearrange before substituting. This is worth its own mark.

Example: A force of 500 N is applied to a trolley of mass 25 kg. Calculate the acceleration.

Step	Working
Equation	F = m x a
Rearrange	a = F / m
Substitution	a = 500 / 25
Answer	a = 20 m/s^2

graph LR
    A[Write Equation] --> B[Substitute Values]
    B --> C[Rearrange if Needed]
    C --> D[Calculate]
    D --> E[State Answer + Unit]
    style E fill:#ccffcc,stroke:#009900

---

Standard Form and Significant Figures

AQA expects you to express answers appropriately. Using standard form and the correct number of significant figures are both assessed.

Standard Form

Standard form is used for very large or very small numbers.

Standard Number	Standard Form
300 000 000 m/s (speed of light)	3.0 x 10^8 m/s
0.000 000 001 m (1 nanometre)	1 x 10^-9 m
6 700 J	6.7 x 10^3 J
0.025 A	2.5 x 10^-2 A

Exam Tip: On a calculator, standard form is entered using the EXP or x10^x button, NOT by typing "x 10 ^". Learn how your specific calculator handles standard form before the exam.

Significant Figures Rules for AQA

AQA has a specific policy on significant figures:

1. Give your answer to the same number of significant figures as the data in the question (or one more significant figure).
2. If the question says "Give your answer to 2 significant figures," you MUST do so — failing to round correctly loses a mark.
3. Do not round intermediate calculations — only round the final answer.
4. If the question does not specify, 2 or 3 significant figures is generally appropriate.

How to Count Significant Figures

Number	Significant Figures	Count
4500	4, 5	2 s.f. (trailing zeros are ambiguous — use standard form: 4.5 x 10^3)
0.0032	3, 2	2 s.f. (leading zeros are not significant)
10.50	1, 0, 5, 0	4 s.f. (trailing zeros after a decimal point are significant)
305	3, 0, 5	3 s.f. (zeros between non-zero digits are significant)

Common Significant Figures Mistakes

Mistake	Example	Correction
Giving too many decimal places	135 000.0000 J	135 000 J or 1.35 x 10^5 J
Rounding too early	Rounding an intermediate step changes the final answer	Keep all digits during calculation; only round the final answer
Ignoring the instruction	Question says "to 2 s.f." but student writes 135 000	Should write 140 000 or 1.4 x 10^5

---

The Equation Sheet: Given vs Must Memorise

Equations You MUST Memorise (NOT on the sheet)

Equation	What It Calculates
E_k = 0.5 x m x v^2	Kinetic energy
E_p = m x g x h	Gravitational potential energy
E_e = 0.5 x k x e^2	Elastic potential energy
E = m x c x delta_T	Energy transfer (specific heat capacity)
P = E / t	Power
Efficiency = useful output / total input	Efficiency
Q = I x t	Charge flow
V = I x R	Ohm's law
P = V x I	Electrical power
P = I^2 x R	Electrical power (alternative)
E = P x t	Energy transferred (electrical)
E = Q x V	Energy transferred (charge)
rho = m / V	Density
W = m x g	Weight
W = F x s	Work done
F = k x e	Hooke's law
s = v x t	Distance (speed equation)
a = delta_v / t	Acceleration
F = m x a	Newton's second law
p = m x v	Momentum
v = f x lambda	Wave speed
T = 1 / f	Period and frequency
V_p / V_s = n_p / n_s	Transformer turns ratio

Equations Given on the Sheet

Equation	What It Calculates
E = m x L	Specific latent heat
p x V = constant	Gas pressure and volume (constant T)
moment = F x d	Moments
p = h x rho x g	Pressure in a column of liquid (Higher)
magnification = image height / object height	Magnification
F = B x I x l	Force on a conductor (Higher)
V_p x I_p = V_s x I_s	Transformer power (Higher)
orbital speed = 2 x pi x r / T	Orbital speed

Exam Tip: In the exam, even if an equation is on the sheet, you must still know how to USE it. The sheet tells you the equation — it does not tell you what the symbols mean or how to rearrange it. Practise using every equation, whether memorised or given.

---

Unit Conversions Students Get Wrong

Unit conversion errors are one of the most common sources of lost marks. AQA questions often give values in non-standard units to test whether you can convert.

Conversion	Rule	Example
kJ to J	Multiply by 1000	5 kJ = 5000 J
J to kJ	Divide by 1000	7500 J = 7.5 kJ
km to m	Multiply by 1000	2.5 km = 2500 m
m to km	Divide by 1000	800 m = 0.8 km
kW to W	Multiply by 1000	3 kW = 3000 W
W to kW	Divide by 1000	1500 W = 1.5 kW
mA to A	Divide by 1000	250 mA = 0.25 A
A to mA	Multiply by 1000	0.6 A = 600 mA
cm to m	Divide by 100	50 cm = 0.5 m
mm to m	Divide by 1000	25 mm = 0.025 m
g to kg	Divide by 1000	500 g = 0.5 kg
hours to seconds	Multiply by 3600	2 hours = 7200 s
minutes to seconds	Multiply by 60	5 minutes = 300 s
km/h to m/s	Divide by 3.6	72 km/h = 20 m/s

Exam Tip: Before substituting into ANY equation, check that all values are in SI units (metres, kilograms, seconds, amperes, volts, joules, watts, etc.). If the question gives 250 mA, you must convert to 0.25 A before using V = I x R.

---

Graph Skills

Graph questions are worth significant marks on both papers. AQA tests several specific skills.