AQA GCSE Combined Science: Trilogy Physics Paper 1 (Higher), 2018: Question 1

✅ Correct answer focus

• Identify parts of the plum pudding and nuclear models.
• Know that protons provide positive charge.
• Use 7% of the speed of light correctly.
• Use the diagram ratio to estimate an атомic radius.

🧠 Exam technique

• Read each label line carefully before choosing from the box.
• For calculations, show the method, not just the answer.
• Use the right units: m/s and m.

❌ Common errors

• Mixing up electron and nucleus .
• Saying “same number of protons and neutrons” instead of same number of protons.
• Forgetting to convert 7% into 0.07.
• Not using the diagram scale in part 01.4.

✅ Correct answers

• Plum pudding model left arrow to a small negative particle: electron
• Plum pudding model left lower arrow to the whole grey sphere: atom
• Nuclear model upper right arrow to the centre: nucleus
• Nuclear model lower right arrow to one of the curved paths: orbit

💡 Key knowledge

• In the plum pudding model, electrons are embedded in a sphere of positive charge.
• In the nuclear model, the nucleus is at the centre and electrons move around it.
• A label must match the arrow position, not just the model.

🧠 Exam technique

• Use each word once only if there are four labels and four blanks.
• If unsure, identify the centre part first: in the nuclear model this is the nucleus .
• Remember: a line pointing to the path is orbit , not electron.

💡 Key knowledge

• The nucleus contains protons and neutrons.
• The number of protons defines the element.
• Atoms of the same element all have the same proton number.

🧠 Exam technique

• For 2 marks, give two separate points:
  1. where positive charge comes from
  2. why it is always the same for that element
• Use the phrase same number of protons .

❌ Common errors

• Do not say “same number of protons and neutrons” — this was specifically not accepted.
• Do not mention electrons as the source of positive charge.
• “Same total charge because atoms are neutral” is not enough on its own.

🧠 What got full marks

Answers that stated protons and same number of protons in atoms of the same element gained both marks clearly.

✅ Correct answer

21 000 000 m/s or 2.1 × 10^7 m/s

🧠 Exam technique

• You can gain method marks even if the final answer is written in standard form.
• Always include m/s.
• Keep the % conversion visible to show your method.

✅ Correct answer

1.5 × 10⁻¹⁰ m

💡 Key knowledge

• This is a scale/ratio question, so you must use the sizes shown in the figure.
• The mark scheme accepted answers in the range 1.4 × 10⁻¹⁰ to 1.6 × 10⁻¹⁰ m.
• A ratio of about 5.7 to 6.3 was accepted.

🧠 Exam technique

• Use the diagram carefully: estimate the diameter or radius consistently.
• If you find the ratio first, multiply the hydrogen radius by that ratio.
• Keep powers of ten neat: 6 × 2.5 × 10⁻¹¹ = 15 × 10⁻¹¹ = 1.5 × 10⁻¹⁰

❌ Common calculation mistakes

• Using the diameter instead of the radius, or mixing them up.
• Forgetting the power of ten when multiplying.
• Giving an answer like 15 × 10⁻¹¹ without simplifying.
• Not using the ratio from the diagram at all.

💡 Remember

• Protons give positive charge.
• Atoms of the same element have the same number of protons.
• 7% means multiply by 0.07.
• In diagrams, use the scale carefully.

🧠 How to score full marks

• Use correct scientific words.
• Show working for calculations.
• Include units.
• Match each label to the correct arrow.