AQA GCSE Physics Physics Paper 1 (Higher), June 2022: Question 7

Mark scheme

Show the mark scheme

AO /

Question Answers Extra information Mark

Spec. Ref.

07.1 two protons and two neutrons allow helium nucleus 1 AO1

4.4.2.1

ignore symbols

AO /

Spec. Ref.

07.2 85 this order only 1 AO1

4.4.2.2

37 1

AO /

Spec. Ref.

AO1

07.3 alpha radiation has a low 1 4.4.2.4

penetrating ability

(so externally) alpha radiation is allow absorbed for stopped 1

stopped by skin (so is low risk) ignore reference to range of

alpha particles through other

materials

internally, alpha radiation is allow (internal) contamination 1

absorbed by living tissue / will increase the radiation dose

organs

(as) alpha radiation is highly 1

ionising

(internal) contamination will allow contamination causes 1

cause greater (risk of) harm to greater chance of developing

cells / tissues / organs / DNA / cancer

genes allow greater chance of

mutations

– HYSICS – –

Total Question 7 8

18Question 8

How to answer it

Nuclear Radiation & Radioactive Decay

What this question tests

This question assesses your recall of the structure of an alpha particle, your ability to balance nuclear decay equations (conserving mass and atomic numbers), and your understanding of the differences in hazard between internal contamination and external irradiation by alpha sources.

Question 07.1

Structure of an Alpha Particle

✅ Correct Answer

Two protons and two neutrons (or a helium nucleus).

💡 Key Knowledge

An alpha particle is identical to a helium nucleus (He-4).
It has a mass number of 4 and an atomic (proton) number of 2.

❌ Common Errors

Writing chemical symbols (like He ) when the question specifically asks "What does an alpha particle consist of?" – always write out words unless symbols are requested.
Confusing alpha particles with beta particles (high-speed electrons).

Mark allocation: 1 mark for stating "two protons and two neutrons" or "helium nucleus".

Question 07.2

Balancing a Beta Decay Equation

✅ Correct Answer

Top box: 85

Bottom box: 37

85 / 36 Kr → 85 / 37 Rb + 0 / -1 e

💡 Key Knowledge

Conservation of Mass Number (Top): Total mass numbers before decay must equal total mass numbers after decay ( 85 = 85 + 0 ).
Conservation of Atomic Number (Bottom): Total charges before must equal totals after ( 36 = 37 + (-1) ).

🧠 Exam Technique

Always check both the top and bottom rows independently. For beta-minus decay, the mass number stays the same, but the atomic number increases by 1 because a neutron turns into a proton.

Mark allocation: 1 mark for top box (85), 1 mark for bottom box (37). Order is strict.

Question 07.3

Contamination vs. Irradiation (Alpha Sources)

✅ Correct Answer

To score full marks, students must contrast external and internal exposure:

Alpha radiation has a low penetrating ability and is stopped by the outer layer of dead skin cells (low external risk).
If internally contaminated, the radioactive material is inside the body, so alpha radiation is directly absorbed by living tissue/organs.
Alpha particles are highly ionising, meaning internal contamination causes a much greater risk of harm, cell mutation, or cancer.

🧠 Exam Technique

This is a 5-mark extended response question. Use comparative language (e.g., "whereas externally...", "in contrast, internally..."). Make sure you link penetration to external safety, and ionising power to internal danger.

❌ Common Errors

Vague statements like "alpha is dangerous inside the body" without explaining why (because it is highly ionising and directly hits living tissue).
Mixing up irradiation (exposure to radiation from a nearby source) with contamination (presence of radioactive atoms on/in an object).

Mark allocation: Up to 5 marks based on a level-of-response or point-by-point marking scheme covering penetration, skin protection, internal absorption, ionising nature, and biological harm (cancer/mutation risk).

Topics

Physics · P4: Atomic Structure