CIE iGCSE Co-Ordinated Science P5.2.4 Half-life Exam Style Questions Paper 3
Question
(a) (i) Complete the sentences to describe the energy changes that occur during the generation of electricity in a nuclear power station.
Nuclear fission releases ………………………………………… energy which heats up water in a boiler.
When the turbine and generator are turning, they have ………………………………………… energy.
The generator produces ………………………………………… energy.
(ii) Nuclear fission occurs in the nuclear power station.
State what happens to the nucleus of an atom during nuclear fission.
(b) The radioactive decay of plutonium-239 produces an isotope of uranium, uranium-235.
plutonium-239 → uranium-235 + α-particle
(i) State the charge on an α-particle.
(ii) Describe how the numbers of protons and neutrons change in the nucleus of a plutonium-239 atom when it emits an α-particle.
protons …………………………………………………………………………
neutrons …………………………………………………………………………
(iii) The half-life of plutonium-239 is 24 000 years.
A sample of nuclear fuel contains 6.0 g of plutonium-239.
Calculate the mass of plutonium-239 remaining after 72 000 years.
mass = ……………………………………………… g
▶️Answer/Explanation
Ans : 6(a)(i) thermal ;
kinetic ;
electrical ;
6(a)(ii) splits ;
6(b)(i) (2) positive ;
6(b)(ii) protons decrease by 2 or down to 92 ;
neutrons decrease by 2 or down to 143 ;
6(b)(iii) 3 half lives ;
6.0 divided by 2 three times ;
0.75 (g) ;
Question
(a) High frequency sound waves are called ultrasound.
An ultrasound wave travels 13.5cm in 0.000090s through water.
Calculate the speed of the ultrasound wave in m/s.
speed = …………………………………………. m/s
(b) Ultrasound waves are used in hospitals to scan unborn babies.
(i) Suggest a reason why it is not safe to scan unborn babies with X-rays.
(ii) State one use for X-rays in a hospital.
(c) (i) γ-radiation is used in hospitals to kill cancerous cells.
Fig. 3.1 shows an incomplete electromagnetic spectrum.
Write γ-radiation in its correct place.
(ii) A source of γ-radiation in a hospital is technetium-99.
Technetium-99 has a half-life of 6 hours.
The source contains 1280 undecayed atoms.
Calculate how many atoms will have decayed after 12 hours.
number of decayed atoms = …………………………………………………
▶️Answer/Explanation
Ans : 3(a) evidence of 13.5 cm = 0.135 m ;
evidence of speed = distance / time (in any form) or 0.135 / 0.000090;
= 1500 (m / s) ;
3(b)(i) ionising radiation damages / kills human cells or damages DNA ;
3(b)(ii) observing broken bones etc ;
3(c)(i) ϒ – radiation on left hand side ;
3(c)(ii) 2 half lives ; (320 remain so ) 960 atoms decayed ;
Question
(a) The list below shows energy sources used by power stations, to generate electricity.
coal gas hydroelectric (HEP)
nuclear petroleum
(i) State the three energy sources from the list that produce carbon dioxide when generating electricity.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
3 ……………………………………………………………………………………………………………………….
(ii) Coal is described as a non-renewable energy source.
Explain what is meant by non-renewable when describing an energy source.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
(iii) State one disadvantage of using nuclear fuel to generate electricity.
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(b) (i) In a nuclear power station, fission of plutonium-239 nuclei takes place.
Describe what happens to the nucleus of a plutonium-239 atom during nuclear fission.
…………………………………………………………………………………………………………………….
(ii) State a safe way of storing a small sample of radioactive material.
………………………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………….
(c) Technetium-99 is a radioactive material. The half-life of technetium-99 is 6 hours.
Calculate the percentage of technetium-99 remaining in a sample after 24 hours.
percentage = ……………………………………………..
▶️Answer/Explanation
Ans: 3(a)(i) any two from:
coal
gas
petroleum ;;
3(a)(ii) only existing as a finite quantity / being used up at a faster rate than it can be replaced ;
3(a)(iii) nuclear accidents / nuclear / dangerous / harmful waste produced ;
3(b)(i) (nucleus) splits ;
3(b)(ii) in a lead lined container ;
3(c) 4 half-lives / division by 16 ;
6.25% ;
Question
(a) Thermal energy is released, by combustion, in a gas-fired power station.
Describe how the thermal energy released is transferred into electrical energy in the power station.
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
(b) State one advantage and one disadvantage of a nuclear power station compared with a gas-fired power station.
advantage …………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………………………
disadvantage …………………………………………………………………………………………………………….
…………………………………………………………………………………………………………………………………
(c) Cobalt-60 is produced in a nuclear power station.
(i) A sample of cobalt-60 has a mass of 2g.
The half-life of cobalt-60 is 5.25 years.
Calculate the mass of cobalt-60 remaining after 21 years.
mass = ……………………………………………… g
(ii) Cobalt-60 decays by emitting β-particles and γ-rays.
State the charge on a β-particle.
charge = ………………………………………………….
(iii) Place α-particles, β-particles and γ-rays in order of their penetrating abilities.
(iv) Suggest a safe way of storing a small sample of cobalt-60.
………………………………………………………………………………………………………………………….
………………………………………………………………………………………………………………………….
▶️Answer/Explanation
Ans: 3(a) thermal energy turns water to steam ;
steam drives turbine ;
turbine drives generator ;
3(b) advantage – nuclear not reliant on fossil fuels / no CO$_{2}$ produced ;
disadvantage – nuclear accidents / disposal of nuclear waste ;
3(c)(i) 4 half-lives ;
0.125 (g) ;
3(c)(ii) –1 ;
3(c)(iii) most penetrating
$\gamma$
β
$\alpha$
least penetrating ;
3(c)(iv) in a lead lined container ;
Question
(a) Fig. 3.1 shows four forces acting on a submarine. The submarine is moving underwater at a constant speed.
State which force A, B, C or D is the weight of the submarine. (Sub-topic – P1.5.1)
▶️Answer/Explanation
Answer: C
Explanation: The weight of the submarine is the force due to gravity acting downward. In the diagram, force C is directed downward, indicating that it represents the weight of the submarine.
(b) The submarine travels 36 km in 2 hours. Calculate the speed of the submarine in m/s. (Sub-topic – P1.2)
▶️Answer/Explanation
Answer: 5 m/s
Explanation:
- Convert 36 km to meters: \( 36 \text{ km} = 36,000 \text{ m} \).
- Convert 2 hours to seconds: \( 2 \text{ hours} = 2 \times 60 \times 60 = 7,200 \text{ s} \).
- Calculate speed using the formula \( \text{speed} = \frac{\text{distance}}{\text{time}} \): \( \text{speed} = \frac{36,000}{7,200} = 5 \text{ m/s} \).
(c) The submarine is powered by a small nuclear reactor. Ionising radiation is released in the reactor. The reactor must be shielded to protect the crew from this radiation. (Sub-topic – P5.2.2)
(i) State how exposure to ionising radiation can affect the human body.
▶️Answer/Explanation
Answer: Cancer / cell mutation
Explanation: Ionising radiation can damage the DNA in cells, leading to mutations that may cause cancer or other harmful effects on the body.
(ii) Suggest a material which can be used to shield a nuclear reactor and stop \(\alpha\)-radiation and \(\beta\)-radiation escaping.
▶️Answer/Explanation
Answer: Lead
Explanation: Lead is a dense material that is effective at blocking \(\alpha\) and \(\beta\) radiation due to its high atomic number and density.
(d) Plutonium-239 (Pu-239) is the nuclear fuel used by the submarine. Pu-239 has a half-life of 24,000 years. A small sample of Pu-239 has a mass of 1.0 g. Calculate the mass of Pu-239 remaining after 96,000 years. (Sub-topic – P5.2.4)
▶️Answer/Explanation
Answer: 0.0625 g
Explanation:
- Determine the number of half-lives in 96,000 years: \( \frac{96,000}{24,000} = 4 \) half-lives.
- Calculate the remaining mass after each half-life: \( 1.0 \text{ g} \rightarrow 0.5 \text{ g} \rightarrow 0.25 \text{ g} \rightarrow 0.125 \text{ g} \rightarrow 0.0625 \text{ g} \).
(e) When it is under the water, the submarine uses a periscope to view a ship on the surface of the sea. Fig. 3.2 shows a simple periscope.
On Fig. 3.2, draw a ray of light from the ship to the observer’s eye to show what happens to the light ray as it passes through the periscope. (Sub-topic – P3.2.1)
▶️Answer/Explanation
Answer: The light ray should reflect off the top mirror and then the bottom mirror before reaching the observer’s eye.
Explanation: In a periscope, light from the ship enters the top mirror, reflects downward to the bottom mirror, and then reflects into the observer’s eye. The ray should be drawn to show these two reflections.
Question
(a) Describe two advantages of generating electricity using nuclear fission compared to generating electricity using fossil fuels. (Sub-topic – P5.1)
▶️Answer/Explanation
Answer:
1. No CO2 emissions, which helps reduce global warming.
2. Fossil fuels are conserved for other purposes, such as transportation and industrial use.
(b) One disadvantage of nuclear power is that nuclear waste is made.
A sample of nuclear waste contains 2.00 g of nickel-63.
(i) The half-life of nickel-63 is 100 years.
Calculate the mass of nickel-63 remaining in the sample after 300 years. (Sub-topic – P5.2.4)
mass = ……………………………………………… g
▶️Answer/Explanation
Answer:
After 300 years (3 half-lives), the mass of nickel-63 remaining = 2.00 g / 23 = 0.25 g
(ii) Suggest a safe way of storing this sample of nuclear waste at a nuclear power station. (Sub-topic – P5.2.5)
▶️Answer/Explanation
Answer:
Store the nuclear waste in lead-lined containers underground.
(iii) Nuclear waste emits ionising radiation.
Fig. 9.1 shows three types of ionising radiation and their descriptions.
Draw lines to link each type of ionising radiation to its correct description.
type of radiation α-particle β-particle γ-ray description electromagnetic wave electron helium nucleus Fig. 9.1 (Sub-topic – P5.2.2)
▶️Answer/Explanation
Answer:
– α-particle: Helium nucleus
– β-particle: Electron
– γ-ray: Electromagnetic wave
(c) In most power stations thermal energy is released and used to heat water. The water is turned into steam.
Fig. 9.2 shows the arrangement of particles in a gas, a liquid and a solid.
State and explain why diagram Y represents a liquid and diagram Z represents a gas. (Sub-topic – P2.1.1)
Diagram Y represents a liquid because …………………………………………………………………………
Diagram Z represents a gas because …………………………………………………………………………..
▶️Answer/Explanation
Answer:
Diagram Y represents a liquid because the particles are randomly arranged and most are touching.
Diagram Z represents a gas because the particles are widely spaced and randomly arranged.