Revision questions
1
Marie Curie realised that the intensity of radiation from uranium was proportional only to the mass of the emitting sample and that nothing could be done to change this.
a What important conclusion did she make from this observation?
b State the reason she was awarded EACH of her two Nobel prizes.
c What important field did her work open for others to develop?
2
Define the following with respect to nuclear emissions:
a radioactivity
b activity of a sample
c becquerel
3
The cloud chamber can be used to identify radioactive emissions.
a Draw diagrams to illustrate the tracks associated with each type of emission.
b Briefly describe and explain these tracks in terms of strength and direction.
4
a State the nature of each of the following:
i \(\alpha\)-particle
ii \(\beta\)-particle
iii \(\gamma\)-wave
b
For each of the following, state the type of radiation (\(\alpha, \beta\) or \(\gamma\)) that has the particular characteristic.
- Has the strongest ionising capability
- Is stopped by a thin sheet of paper or a few cm of air
- Has the strongest penetrating capability
- Cannot be deflected by an electric or a magnetic field
- Is deflected most by an electric or a magnetic field
- Can penetrate no more than a few mm of aluminium
- Is a particle of relative charge \(+2\)
- Is a particle of charge \(-1.6 \times 10^{-19} \text{ C}\)
- Is comprised of particles of total charge \(+3.2 \times 10^{-19} \text{ C}\)
- Is comprised of particles of total mass more than \(7000\) times that of an electron
5
a What is meant by background radiation?
b Identify THREE sources of background radiation.
6
Describe an experiment, using EACH of the methods listed below, to determine the type of radiation being emitted by a radioactive source.
a absorption test
b electric field deflection test
c magnetic field deflection test
7
State the numbers that should replace the boxes in the following nuclear equations.
a \({}^{214}_{84}\text{Po} \to \alpha + {}^{\square}_{\square}\text{Pb}\)
b \({}^{210}_{82}\text{Pb} \to \beta + {}^{\square}_{\square}\text{Bi}\)
c \({}^{99m}_{43}\text{Tc} \to \gamma + {}^{\square}_{\square}\text{Tc}\)
8
A mass of \(4.0 \text{ g}\) of iodine-131 (I-131), of half-life \(8\) days, decays for a period of \(24\) days.
a Define the term half-life.
b What mass of I-131 remains after this time?
c Sketch a graph of mass against time for the decay.
9
A sample of the metal sodium-24 (Na-24) at a temperature of \(20 \text{ °C}\) is left for a period of \(30\) hours. After this time its activity falls by \(75\%\).
a Determine the half-life of Na-24.
b What would be the half-life if the temperature was \(40 \text{ °C}\)?
c Would the half-life be affected if the sample was in the form of the compound NaCl?
10
It is said that radioactivity is a random process.
a How can the use of a Geiger tube and accessories be used to verify this random nature?
b How can an experimental plot of count rate against time illustrate the random nature?
11
A sample of \(1.0 \text{ g}\) of carbon from a live plant gives a count rate of \(20 \text{ min}^{-1}\). The same mass of carbon is analysed from an old relic and gives a count rate of \(5 \text{ min}^{-1}\).
a Assuming the half-life of C-14 to be \(5700\) years, determine the age of the relic.
b Why is C-14 dating not useful for ageing specimens over \(60\,000\) years old?
12
a Briefly describe the use of the following in the medical field, stating a suitable radionuclide in each case:
i tracers
ii external beam radiotherapy
b State TWO problems with the use of external beam radiotherapy.
13
The following is about radioisotopes used in the medical field.
a Explain why the half-life of a radioisotope given orally or by injection to a patient must be short, but not too short.
b Name the type of radioactive emission that is least absorbed by the body.
In questions 14, 15 and 16 use: speed of light in a vacuum \(c = 3.0 \times 10^8 \text{ m s}^{-1}\).
14
\(1 \text{ g}\) of matter is completely transformed into energy.
a Write the equation needed to calculate the amount of energy produced.
b Identify each quantity in the equation.
c Name the scientist associated with this equation.
d Calculate the energy derived from the mass.
15
A certain star is losing mass at a rate of \(2.0 \times 10^8 \text{ kg s}^{-1}\). Determine its power output.
16
Determine the energy released during the fusion of the hydrogen nuclei shown below:
\({}^{2}_{1}\text{H} + {}^{2}_{1}\text{H} \to {}^{3}_{2}\text{He} + {}^{1}_{0}\text{n}\)
(\({}^{2}_{1}\text{H} = 3.345 \times 10^{-27} \text{ kg}\), \({}^{3}_{2}\text{He} = 5.008 \times 10^{-27} \text{ kg}\), \({}^{1}_{0}\text{n} = 1.675 \times 10^{-27} \text{ kg}\))
17
Briefly describe TWO advantages and TWO disadvantages of obtaining electricity from nuclear energy.
18
Alpha, beta and gamma radiation are ionising radiations.
a Briefly describe the effects of ionising radiation on body cells.
b Suggest a reason why a gamma source is usually less dangerous than an alpha or beta source when ingested or inhaled.
c State THREE precautions that can be taken as protection against the hazards of ionising radiations.
19
a Define: (i) nuclear fusion (ii) nuclear fission.
b Why do nuclei undergo fission?
c Name the process by which the Sun liberates energy.
d Name the process by which today’s nuclear power stations generate electricity.
20
State the numbers that should replace the boxes in this nuclear equation:
\({}^{\square}\text{U} + {}^{1}_{0}\text{n} \to {}^{139}_{56}\text{Ba} + {}^{\square}_{36}\text{Kr} + 3{}^{1}_{0}\text{n} + \text{energy}\)
Exam-style questions
Structured questions
1
a)
Complete Table 1 with reference to the nucleus of a carbon atom, \({}^{14}_{6}\text{C}\).
Table 1
| Mass number | |
| Atomic number | |
| An isotope (represented in a similar manner) | |
| Number of electron shells in its atom | |
| Number of electrons in its neutral atom | |
(5 marks)
b)
Complete Table 2 to show the mass and charge of the neutron and the electron relative to that of the proton.
Table 2
| proton | neutron | electron |
| Relative mass | 1 | | |
| Relative charge | +1 | | |
(2 marks)
c)
Carbon-14 is used to determine the age of old organic material. It has a half-life of \(5700\) years. In natural carbon there is ONE atom of C-14 with every \(8 \times 10^{11}\) atoms of carbon.
- What percentage of a sample of the isotope remains after a period of \(17\,100\) years? (2 marks)
- Predict whether or not the isotope would be useful in determining the age of a specimen older than \(60\,000\) years. (2 marks)
- A sample of carbon-14 is heated in a furnace so that its constituent atoms obtain increased kinetic energy. By applying your knowledge of nuclear processes, predict how the half-life of the isotope is affected. (2 marks)
- C-14 decays by emission of a beta particle to form N-14. Write a nuclear equation for the decay. (2 marks)
Total 15 marks
2
a)
Complete Table 3 with reference to the properties of radioactive emissions.
Table 3
| Property |
Type of emission |
| Tracks produced in a cloud chamber are thick and straight | |
| Travels at the speed of light in a vacuum | |
| Strongly ionises the air it passes through | |
| Penetrates up to a few mm of aluminium | |
| Is deflected most by magnetic fields | |
| On emission, produces an element one place ahead in the Periodic Table | |
| Is electromagnetic in nature | |
(7 marks)
b)
Calculate the values of \(p, q, r, s\) and \(t\) in the following nuclear disintegrations, and rewrite the equations:
\({}^{210}_{82}\text{Pb} \to {}^{0}_{-1}\text{e} + {}^{p}_{q}\text{Bi}\)
\({}^{p}_{q}\text{Bi} \to {}^{0}_{-1}\text{e} + {}^{r}_{s}\text{Po}\)
\({}^{r}_{s}\text{Po} \to {}^{4}_{2}\text{He} + {}^{206}_{t}\text{Pb}\)
(4 marks)
c)
A ratemeter detects a background count rate of \(5 \text{ Bq}\). When a radioactive source is placed close to its detecting window, it detects a count rate of \(85 \text{ Bq}\). If the half-life of the source is \(20\) minutes, what will be the count rate received after a period of \(1\) hour?
(4 marks)
Total 15 marks
Extended response questions
3
a)
The ‘gold-foil’ experiment carried out by Geiger and Marsden revealed a better understanding of the structure of an atomic nucleus.
- Briefly describe the procedure.
- State TWO important observations of the experiment.
- State TWO conclusions drawn from the observations. (6 marks)
b)
Iodine-131 (I-131) has an atomic number of 53 and is a beta-emitter with a half-life of 8 days. It decays to the element xenon, Xe.
- Write a nuclear equation for its decay. (3 marks)
- 160 g of iodine-131 is left in a sealed container in the laboratory. Calculate the mass of the sample remaining after a period of 40 days. (3 marks)
- Sketch a graph of mass against count rate for the first 24 days. (3 marks)
Total 15 marks
4
a)
State THREE advantages and THREE disadvantages of generating electricity in nuclear power stations. (6 marks)
b)
i) The equation of the fusion reaction of deuterium, an isotope of hydrogen, is shown below. Table 4 indicates the atomic masses of the particles involved in the reaction.
$${}^{2}_{1}\text{H} + {}^{2}_{1}\text{H} \to {}^{3}_{2}\text{He} + {}^{1}_{0}\text{n} + \text{energy}$$
Table 4
| Nuclide |
Atomic mass/u |
| $${}^{2}_{1}\text{H}$$ |
2.015 |
| $${}^{3}_{2}\text{He}$$ |
3.017 |
| $${}^{1}_{0}\text{n}$$ |
1.009 |
Calculate the energy released by the fusion reaction of two deuterium nuclei.
(\(1 \text{ u} = 1.66 \times 10^{-27} \text{ kg}\), \(c = 3.0 \times 10^8 \text{ m s}^{-1}\)) (5 marks)
ii)
Determine the number of neutrons released in the nuclear reaction shown below. (1 mark)
$${}^{235}_{92}\text{U} + {}^{1}_{0}\text{n} \to {}^{148}_{57}\text{La} + {}^{85}_{35}\text{Br} + \text{neutrons}$$
c)
A certain star loses mass at a rate of \(5.0 \times 10^9 \text{ kg s}^{-1}\). Calculate its power output.
(Speed of light in a vacuum \(= 3.0 \times 10^8 \text{ m s}^{-1}\)) (3 marks)
