AQA GCSE Combined Science: Trilogy Biology Paper 2 (Higher), 2019: Question 1

✅ Correct answers

• Hold a ruler just above the open hand of the other student.
• Drop the ruler without warning.
• The other student catches it.
• Record where the ruler is caught.

💡 Key knowledge

• The test measures reaction time.
• A shorter catching distance means a faster reaction.
• The same method should be repeated to improve reliability.

🧠 Exam technique

• Write the steps in order.
• Use simple practical language: hold → drop → catch → measure .
• For full marks, describe what the person does, not just “do the test”.

❌ Common errors

• Giving a verbal signal — this was not allowed.
• Measuring the time instead of the distance.
• Not saying that the ruler is caught by the other student.

📐 Calculation

Given: 32.25 mg of caffeine in 100 cm³

Group D drank: 600 cm³

1. Find the mass in 1 cm³: 32.25 ÷ 100 = 0.3225 mg
2. Multiply by 600: 0.3225 × 600 = 193.5 mg

Answer: 193.5 mg

✅ Correct answer

X = 193.5 mg

🧠 Exam technique

• Use proportional reasoning carefully.
• Keep units with the calculation.
• Show the working even for 1 mark — it helps avoid slips.

❌ Common errors

• Forgetting to scale from 100 cm³ to 600 cm³.
• Writing the answer as 1935 mg or 19.35 mg.
• Losing the units.

✅ Correct answer

To compare the effect of no caffeine.

💡 Key knowledge

• A control group gives a baseline to compare against.
• This shows whether caffeine changes reaction time.

🧠 Exam technique

• Link your answer to the purpose of a control.
• Use “compare” or “show the effect of caffeine” for full credit.

📐 Calculation

From Table 2:

• 22 cm = 0.212 s
• 24 cm = 0.221 s

1. 23 cm is halfway between 22 cm and 24 cm.
2. So the reaction time is halfway between 0.212 and 0.221.
3. Estimate: about 0.217 s.

✅ Correct answer

0.217 s

🧠 Exam technique

• Use interpolation: choose the two nearest values.
• Make sure the answer is in seconds.
• For this table, a sensible estimate is enough.

❌ Common errors

• Using 20 cm and 24 cm instead of the nearest values.
• Not giving a sensible estimate between the two values.
• Writing the answer in cm instead of seconds.

✅ Correct answer

As the mass of caffeine increases, the decrease in reaction time increases.

💡 Key knowledge

• Higher caffeine dose generally gives a bigger improvement in reaction time.
• The graph shows a positive trend overall.

🧠 Exam technique

• Use the data trend, not just one point.
• Use comparative words: as... increases, ... increases .

❌ Common errors

• Saying “caffeine decreases reaction time” without linking to the graph trend.
• Confusing decrease in reaction time with reaction time itself.
• Describing only group D or only group A.

✅ Correct answer

Their reaction time was greater after the drink.

💡 Key knowledge

• A negative decrease means the value went up, not down.
• So the student reacted more slowly after drinking.

❌ Common errors

• Calling it an anomalous result — not enough for this mark.
• Saying “they improved” when the value was negative.

📐 Calculation

From the scatter graph, group C results are about:

• lowest ≈ 0.01 s
• highest ≈ 0.18 s

Range = highest − lowest = 0.18 − 0.01 = 0.17 s

✅ Correct answer

0.17 s

🧠 Exam technique

• Range = highest value − lowest value.
• Read the points carefully from the graph.
• Units are usually not required here, but it is fine to include s .

❌ Common errors

• Subtracting the wrong way round is okay if you give the size of the range.
• Using the spread of all groups instead of just group C.
• Reading the graph inaccurately.

✅ Correct answers

Any two of the following:

• same age range
• same sex / gender
• same height / weight / BMI
• all had no caffeine / medication / drugs earlier that day
• equally tired or same amount of sleep
• practice of the ruler drop test
• starting point of ruler / hand
• same point to take measurement above / below the thumb / finger
• using the same hand
• same number of students in each group

💡 Key knowledge

• Control variables make it a fair test.
• Only caffeine should change between groups.

🧠 Exam technique

• Choose variables that could affect reaction time.
• Write them clearly as specific controls, not vague statements like “keep it the same”.

❌ Common errors

• Writing “volume of caffeine” or “concentration of caffeine” — these were not accepted as controls here.
• Repeating the independent variable.

✅ Correct answer

It is not automatic because it involves the conscious part of the brain.

💡 Key knowledge

• Reflexes are automatic.
• The ruler-drop test needs a decision to catch the ruler.

🧠 Exam technique

• Compare with a reflex: reflex = automatic, fast, not consciously controlled.
• Use the word conscious or voluntary for the mark.

❌ Common errors

• Saying “because it is quick” — speed alone does not make it a reflex.
• Saying “it uses muscles” — reflexes also use muscles.
• Calling it a reflex because it is a reaction test.

💡 What top answers did well

• Used the correct scientific term: control group, voluntary action, range.
• Read the table and graph carefully.
• Gave clear, short answers matched to the marks.

🧠 Best exam habits

• Use the information given in the question.
• Show your calculation steps.
• For graph questions, quote values and describe the trend.