AQA GCSE Combined Science: Trilogy Physics Paper 1 (Foundation), 2024: Question 3
8 marks · Low Demand difficulty · Short Answer
Analyze radioactive isotopes of radium, including their atomic structure, half-life determination from a graph, experimental variables, and radiation hazards.
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Question text
03 Some people used to think that radioactive substances had health benefits.
100 years ago, a company made toothpaste containing the radioactive isotopes
radium-228 and radium-226.
Figure 3 shows the symbols for these isotopes.
Figure 3
03.1 How are atoms of radium-228 different from atoms of radium-226?
[1 mark]
Tick ( ) one box.
Radium-228 atoms have one more neutron and one more proton.
Radium-228 atoms have two more neutrons and two more protons.
Radium-228 atoms have two more neutrons.
Radium-228 atoms have two more protons.11
03.2 Figure 4 shows how the activity of a sample of radium-228 changed over time.
Figure 4
What is the approximate half-life of radium-228?
[1 mark]
Tick ( ) one box.
*10* 6 years
7 years
14 years
100 years 12
A scientist investigated whether the toothpaste in four tubes of the 100-year-old
toothpaste is equally radioactive.
Figure 5 shows the equipment used.
Figure 5
03.3 When the equipment was arranged as shown in Figure 5, it was not possible to
detect alpha particles from the toothpaste.
Suggest how the scientist adjusted the equipment to detect alpha particles from
the toothpaste.
[1 mark]
03.4 The scientist adjusted the equipment and determined the activity of the toothpaste
from each tube.
Table 1 shows the results.
Table 1
Tube Activity in Bq
A 3150
B 2940
C 3180
D 3050
What was the range of activities shown in Table 1?
[1 mark]
From Bq to Bq
03.5 What was the independent variable in the investigation?
[1 mark]
Tick ( ) one box.
The activity of the toothpaste
The mass of toothpaste used
The temperature of the toothpaste
The tube of toothpaste used 14
03.6 What was the dependent variable in the investigation?
[1 mark]
Tick ( ) one box.
The activity of the toothpaste
The mass of toothpaste used
*13* The temperature of the toothpaste
The tube of toothpaste used
03.7 When the toothpaste was new, it caused a risk to health because of the nuclear
radiation emitted.
What happened to the risk to health from the toothpaste after 100 years?
[1 mark]
03.8 Which property makes nuclear radiation hazardous?
[1 mark]
Tick ( ) one box.
Nuclear radiation is ionising.
Nuclear radiation is penetrating.
Nuclear radiation is too small to see.
Nuclear radiation makes objects radioactive.
Mark scheme
Show the mark scheme
Question 3
AO /
Question Answers Extra information Mark
Spec. Ref.
03.1 radium-228 atoms have two 1 AO1
more neutrons 6.4.1.2
AO /
Spec. Ref.
03.2 6 years 1 AO2
6.4.2.3
AO /
Spec. Ref.
03.3 decrease the distance between 1 AO3
the toothpaste and the detector 6.4.2.1
AO /
Spec. Ref.
03.4 2940 answers may be in either order 1 AO3
6.4.2.1
3180
AO /
Spec. Ref.
03.5 the tube of toothpaste used 1 AO3
6.4.2.1
AO /
Spec. Ref.
03.6 the activity of the toothpaste 1 AO3
– – – 6.4.2.1
AO /
Spec. Ref.
03.7 there is less risk 1 AO3 11
6.4.2.4
AO /
Spec. Ref.
03.8 nuclear radiation is ionising 1 AO1
6.4.2.1
6.4.2.4
Total Question 3 8
How to answer it
Radioactivity and Isotopes in Toothpaste
What this question tests
This question assesses your understanding of atomic structure (isotopes), interpreting decay graphs to find half-life, the properties of alpha radiation, and the basics of scientific investigations (variables and data range).
Comparing Isotopes
Key Knowledge
- Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
- The bottom number (88) is the atomic number (protons).
- The top number is the mass number (protons + neutrons).
The Calculation
- Mass of Isotope A: 228
- Mass of Isotope B: 226
- Difference: 228 - 226 = 2
- Since the atomic number (88) is the same, this difference must be 2 neutrons.
Correct Answer
Radium-228 atoms have two more neutrons.
Finding Half-Life from a Graph
Exam Technique
To find half-life from an activity graph:
- Find the starting activity at Time = 0 (200 Bq).
- Divide that number by two (100 Bq).
- Draw a horizontal line from 100 Bq to the curve.
- Draw a vertical line down to the time axis.
Correct Answer
6 years
1 Mark: Awarded for correctly identifying the time it takes for activity to drop from 200 to 100.
Alpha Radiation Range
Key Knowledge
Alpha particles (α) are highly ionising but have a very short range in air (usually only 3 to 5 cm). They are also stopped by a thin sheet of paper.
Examiner Insight
The diagram shows the detector is 20 cm away from the sample. Because alpha particles only travel a few centimetres, they cannot reach the detector at this distance.
Correct Answer
Decrease the distance between the toothpaste and the detector.
Common Error
Students often suggest "using a different detector." This is wrong because the issue isn't the machine; it's the physical property of the radiation being unable to travel through 20cm of air.
Data and Variables
03.4: Range
The "range" is simply the lowest value and the highest value in the data set.
From 2940 Bq to 3180 Bq
03.5 & 03.6: Variables
- Independent Variable: The thing you change (The tube of toothpaste used).
- Dependent Variable: The thing you measure (The activity of the toothpaste).
Risk and Hazards
03.7: Risk over Time
As time passes, radioactive nuclei decay. This means the activity decreases. If there is less radiation being emitted, the risk to health decreases.
Correct Answer: There is less risk / the risk decreased.
03.8: Why is radiation hazardous?
Nuclear radiation is ionising. This means it can knock electrons off atoms in your cells, which can damage DNA and lead to mutations or cancer.
Common Misconception
Do not say radiation "makes objects radioactive." This is contamination or irradiation, but the hazard itself comes from the ionising nature of the rays/particles.
Topics
Physics · P4: Atomic Structure
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 1 (Foundation), 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.