Define mass-energy equivalence .

The principle that mass can be converted into energy , and energy can be converted into mass.

State four examples of processes where mass-energy equivalence is significant.

The fusion of hydrogen into helium in the centre of the sun The fission of uranium in nuclear power plants Nuclear weapons High-energy particle collisions in particle accelerators

The daughter nuclei produced in fission and fusion have a .......... binding energy per nucleon than the parent nuclei.

The daughter nuclei produced in fission and fusion have a higher binding energy per nucleon than the parent nuclei.

True or False? Einstein's mass-energy equivalence shows that mass can be converted into energy, but energy cannot be converted back into mass.

False. Mass-energy equivalence works in both directions — mass can be converted into energy, and energy can be converted into mass.

Define annihilation .

When a particle meets its equivalent anti-particle , they are both destroyed and their mass is converted into energy in the form of two gamma-ray photons .

Define pair production .

When a photon interacts with a nucleus or atom and the energy of the photon is used to create a particle-antiparticle pair .

Why must pair production take place close to a nucleus?

So that the process conserves both energy and momentum . A single photon alone cannot produce a particle-antiparticle pair, or the conservation laws would be broken.

True or False? When an electron and positron annihilate, only one gamma-ray photon is produced.

False. Two gamma-ray photons are produced, emitted in opposite directions , so that momentum is conserved.

The difference between the measured mass of a nucleus and the sum total of the masses of its constituents.

Define binding energy .

The energy required to break a nucleus into its constituent protons and neutrons .

Define binding energy per nucleon .

The binding energy of a nucleus divided by the number of nucleons in the nucleus.

True or False? The binding energy of a nucleus is the energy stored within the nucleus.

False. Binding energy is not stored energy — it is the energy that must be put into the nucleus to pull it apart into its constituent nucleons.

Which nuclide has the highest binding energy per nucleon, and what does this indicate about it?

Iron-56 (A = 56) has the highest binding energy per nucleon, making it the most stable of all the elements.

Name three nuclides that do not fit the general trend of the binding energy per nucleon graph.

Helium-4 , carbon-12 and oxygen-16 . Helium-4 is particularly stable, while carbon-12 and oxygen-16 can be considered as three and four helium nuclei bound together, respectively.

At high values of nucleon number A , the heaviest elements are the most unstable and likely to undergo ..........

At high values of nucleon number A , the heaviest elements are the most unstable and likely to undergo fission

In the mass defect equation, ( A – Z ) represents the number of .......... in the nucleus.

In the mass defect equation, ( A – Z ) represents the number of neutrons in the nucleus.

What does m total represent in the mass defect equation?

The measured (actual) mass of the nucleus.

True or False? The mass defect of a nucleus is found by adding the measured mass of the nucleus to the total mass of its individual protons and neutrons.

False. Mass defect is the difference between the sum of the masses of the individual protons and neutrons and the measured mass of the nucleus, not their sum.

Once binding energy has been calculated in joules, how is it converted to MeV?

Divide by 1.6 × 10 -19 to convert J to eV Divide by 10 6 to convert eV to MeV

Define nuclear fission .

The splitting of a large, unstable nucleus into two smaller nuclei.

Besides two daughter nuclei, what else is produced during nuclear fission?

Two or three neutrons , and gamma rays .

Define spontaneous fission .

Nuclear fission that occurs without additional energy being put into the nucleus. It is rare.

Define induced fission .

Fission that occurs after an unstable nucleus absorbs a neutron , for example uranium-235 absorbing a neutron to form uranium-236, which is highly unstable and splits almost immediately.

Define a chain reaction .

A process in which the neutrons released by each fission event go on to induce further fission events, each of which releases more neutrons.

As the fission products move apart rapidly, energy is transferred from nuclear potential energy to .......... energy.

As the fission products move apart rapidly, energy is transferred from nuclear potential energy to kinetic energy.

True or False? Uranium-235 usually undergoes fission spontaneously, without needing to absorb a neutron first.

False. Uranium-235 has a very long half-life (700 million years), so spontaneous fission is rare . It normally requires induced fission — absorbing a neutron to become unstable uranium-236, which then splits almost immediately.

What is the purpose of the moderator in a fission reactor?

To slow down fast-moving neutrons, by colliding them with the moderator's molecules, so they are in thermal equilibrium and can react efficiently with the uranium fuel.

What is the purpose of control rods , and how do they adjust the rate of fission?

Control rods absorb neutrons . Lowering the rods decreases the fission rate (more neutrons absorbed); raising the rods increases the fission rate (fewer neutrons absorbed).

What is the purpose of the coolant in a fission reactor?

To remove the heat released by the fission reactions and carry it to an external boiler, where steam is produced to power electricity-generating turbines.

Define high-level radioactive waste .

The unusable fission products from spent fuel rods. It is the most dangerous type of waste, remaining radioactive for thousands of years , and is also extremely hot.

Describe how high-level radioactive waste is treated, from removal to final storage.

Cooled in ponds of water near the reactor for a number of years Plutonium and uranium isotopes are harvested for reuse Mixed with molten glass and solidified ( vitrification ) Encased in containers of steel, lead or concrete Stored very deep underground

Low-level radioactive waste must be encased in .......... and stored a few metres underground until it can be disposed of with regular waste.

Low-level radioactive waste must be encased in concrete and stored a few metres underground until it can be disposed of with regular waste.

True or False? Uranium-238 within fuel rods decays into plutonium-239, which is only mildly radioactive and decays quickly.

False. Plutonium-239 is extremely radioactive with a long half-life of 24 000 years , so it decays slowly and presents a contamination risk for a very long time.

Define nuclear fusion .

Nuclear fusion is the process in which small nuclides combine together to form larger nuclei, releasing energy.

What nuclei fuse in the deuterium-tritium (D-T) reaction studied on Earth, and what are the products?

A deuterium nucleus fuses with a tritium nucleus to produce a helium nucleus and a neutron .

Why does fusion require extremely hot, dense environments, such as the core of a star?

Fusing nuclei must have high kinetic energy to overcome the electrostatic repulsion between positively charged protons; this is only achieved in extremely hot and dense environments.

When two hydrogen nuclei fuse to form deuterium, a .......... and an electron neutrino are also produced, as one proton converts into a neutron by beta-plus decay.

When two hydrogen nuclei fuse to form deuterium, a positron and an electron neutrino are also produced, as one proton converts into a neutron by beta-plus decay.

True or False? In the centres of stars, four helium nuclei fuse together to produce one hydrogen nucleus.

False. It is the reverse: four hydrogen nuclei fuse to produce one helium nucleus , releasing energy that fuels the star.

Why is energy released during a fusion reaction?

The mass of the new, heavier nucleus is less than the total mass of the original nuclei; this mass difference is converted into energy , and the binding energy per nucleon increases.

What do nuclear equations represent, and what other type of equation are they similar to?

Nuclear equations represent nuclear reactions, such as fission and fusion ; they are similar to chemical equations in Chemistry .

What two quantities must balance on either side of a nuclear equation?

The nucleon numbers (top numbers) and the proton numbers (bottom numbers) must each balance on both sides.

In a nuclear equation, the sum of the .......... numbers (top numbers) must be equal on both sides of the equation.

In a nuclear equation, the sum of the nucleon numbers (top numbers) must be equal on both sides of the equation.

When a uranium-235 nucleus is struck by a neutron and undergoes fission into strontium and xenon nuclei, what else is released?

Two neutrons are released, along with energy.

How can balancing a nuclear equation be used to find an unknown quantity, such as the number of neutrons released in a reaction?

By ensuring the total nucleon number and proton number are equal on both sides, any unknown coefficient (e.g. the number of neutrons emitted) can be calculated.

True or False? Only the nucleon (top) numbers need to balance in a nuclear equation; the proton (bottom) numbers do not need to.

False. Both the nucleon numbers and the proton numbers must balance on each side of a nuclear equation.

A LevelPhysicsOCRFlashcards6. Particles & Medical PhysicsNuclear Fission & Fusion

Nuclear Fission & Fusion (OCR A Level Physics): Flashcards

Exam code: H556

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FrontEnergy & Mass Equation
Define mass-energy equivalence.
FrontEnergy & Mass Equation
State the mass-energy equivalence equation and identify each symbol.
BackEnergy & Mass Equation
$E = m c^{2}$
E = energy (J)
m = mass (kg)
c = speed of light (m s^-1)
FrontEnergy & Mass Equation
State four examples of processes where mass-energy equivalence is significant.
BackEnergy & Mass Equation
The fusion of hydrogen into helium in the centre of the sun
The fission of uranium in nuclear power plants
Nuclear weapons
High-energy particle collisions in particle accelerators

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Cards in this collection (51)

Define mass-energy equivalence.
The principle that mass can be converted into energy, and energy can be converted into mass.
State the mass-energy equivalence equation and identify each symbol.
$E = m c^{2}$
- E = energy (J)
- m = mass (kg)
- c = speed of light (m s^-1)
State four examples of processes where mass-energy equivalence is significant.
- The fusion of hydrogen into helium in the centre of the sun
- The fission of uranium in nuclear power plants
- Nuclear weapons
- High-energy particle collisions in particle accelerators
The daughter nuclei produced in fission and fusion have a .......... binding energy per nucleon than the parent nuclei.
The daughter nuclei produced in fission and fusion have a higher binding energy per nucleon than the parent nuclei.
True or False?
Einstein's mass-energy equivalence shows that mass can be converted into energy, but energy cannot be converted back into mass.
False.
Mass-energy equivalence works in both directions — mass can be converted into energy, and energy can be converted into mass.
Which equation calculates the energy released in a nuclear reaction from the mass defect, and what does Δm represent?
$E = (Δ m) c^{2}$
Δm is the mass defect (kg).
Define annihilation.
When a particle meets its equivalent anti-particle, they are both destroyed and their mass is converted into energy in the form of two gamma-ray photons.
Define pair production.
When a photon interacts with a nucleus or atom and the energy of the photon is used to create a particle-antiparticle pair.
Why must pair production take place close to a nucleus?
So that the process conserves both energy and momentum. A single photon alone cannot produce a particle-antiparticle pair, or the conservation laws would be broken.
What is the minimum total photon energy required to create a particle-antiparticle pair, in terms of the rest mass Δm?
$2 Δ E = 2 (c^{2} Δ m)$
The photon energy must be at least twice the rest-mass energy of the pair.
The energy carried by each photon produced during annihilation is given by E_photon = hf = $\frac{h c}{λ}$ = ..........
The energy carried by each photon produced during annihilation is given by E_photon = hf = $\frac{h c}{λ}$ = c²Δ*m*
True or False?
When an electron and positron annihilate, only one gamma-ray photon is produced.
False.
Two gamma-ray photons are produced, emitted in opposite directions, so that momentum is conserved.
Define mass defect.
The difference between the measured mass of a nucleus and the sum total of the masses of its constituents.
Define binding energy.
The energy required to break a nucleus into its constituent protons and neutrons.
Define binding energy per nucleon.
The binding energy of a nucleus divided by the number of nucleons in the nucleus.
True or False?
The binding energy of a nucleus is the energy stored within the nucleus.
False.
Binding energy is not stored energy — it is the energy that must be put into the nucleus to pull it apart into its constituent nucleons.
Which nuclide has the highest binding energy per nucleon, and what does this indicate about it?
Iron-56 (A = 56) has the highest binding energy per nucleon, making it the most stable of all the elements.
Name three nuclides that do not fit the general trend of the binding energy per nucleon graph.
Helium-4, carbon-12 and oxygen-16. Helium-4 is particularly stable, while carbon-12 and oxygen-16 can be considered as three and four helium nuclei bound together, respectively.
At high values of nucleon number A, the heaviest elements are the most unstable and likely to undergo ..........
At high values of nucleon number A, the heaviest elements are the most unstable and likely to undergo fission
What equation is used to calculate binding energy, ΔE, from the mass defect, Δm?
$Δ E = c^{2} Δ m$
What equation is used to calculate the mass defect, Δm, of a nucleus?
$Δ m = Z m_{p} + (A - Z) m_{n} - m_{t o t a l}$
- Z = proton number
- A = nucleon number
- m_p = mass of a proton (kg)
- m_n = mass of a neutron (kg)
- m_total = measured mass of the nucleus (kg)
In the mass defect equation, (A – Z) represents the number of .......... in the nucleus.
In the mass defect equation, (A – Z) represents the number of neutrons in the nucleus.
What does m_total represent in the mass defect equation?
The measured (actual) mass of the nucleus.
True or False?
The mass defect of a nucleus is found by adding the measured mass of the nucleus to the total mass of its individual protons and neutrons.
False.
Mass defect is the difference between the sum of the masses of the individual protons and neutrons and the measured mass of the nucleus, not their sum.
Once binding energy has been calculated in joules, how is it converted to MeV?
- Divide by 1.6 × 10^-19 to convert J to eV
- Divide by 10⁶ to convert eV to MeV
Define nuclear fission.
The splitting of a large, unstable nucleus into two smaller nuclei.
Besides two daughter nuclei, what else is produced during nuclear fission?
Two or three neutrons, and gamma rays.
Define spontaneous fission.
Nuclear fission that occurs without additional energy being put into the nucleus. It is rare.
Define induced fission.
Fission that occurs after an unstable nucleus absorbs a neutron, for example uranium-235 absorbing a neutron to form uranium-236, which is highly unstable and splits almost immediately.
Define a chain reaction.
A process in which the neutrons released by each fission event go on to induce further fission events, each of which releases more neutrons.
As the fission products move apart rapidly, energy is transferred from nuclear potential energy to .......... energy.
As the fission products move apart rapidly, energy is transferred from nuclear potential energy to kinetic energy.
True or False?
Uranium-235 usually undergoes fission spontaneously, without needing to absorb a neutron first.
False.
Uranium-235 has a very long half-life (700 million years), so spontaneous fission is rare. It normally requires induced fission — absorbing a neutron to become unstable uranium-236, which then splits almost immediately.
What is the purpose of the moderator in a fission reactor?
To slow down fast-moving neutrons, by colliding them with the moderator's molecules, so they are in thermal equilibrium and can react efficiently with the uranium fuel.
What is the purpose of control rods, and how do they adjust the rate of fission?
Control rods absorb neutrons. Lowering the rods decreases the fission rate (more neutrons absorbed); raising the rods increases the fission rate (fewer neutrons absorbed).
What is the purpose of the coolant in a fission reactor?
To remove the heat released by the fission reactions and carry it to an external boiler, where steam is produced to power electricity-generating turbines.
Define high-level radioactive waste.
The unusable fission products from spent fuel rods. It is the most dangerous type of waste, remaining radioactive for thousands of years, and is also extremely hot.
Describe how high-level radioactive waste is treated, from removal to final storage.
- Cooled in ponds of water near the reactor for a number of years
- Plutonium and uranium isotopes are harvested for reuse
- Mixed with molten glass and solidified (vitrification)
- Encased in containers of steel, lead or concrete
- Stored very deep underground
Low-level radioactive waste must be encased in .......... and stored a few metres underground until it can be disposed of with regular waste.
Low-level radioactive waste must be encased in concrete and stored a few metres underground until it can be disposed of with regular waste.
True or False?
Uranium-238 within fuel rods decays into plutonium-239, which is only mildly radioactive and decays quickly.
False.
Plutonium-239 is extremely radioactive with a long half-life of 24 000 years, so it decays slowly and presents a contamination risk for a very long time.
Define nuclear fusion.
Nuclear fusion is the process in which small nuclides combine together to form larger nuclei, releasing energy.
What nuclei fuse in the deuterium-tritium (D-T) reaction studied on Earth, and what are the products?
A deuterium nucleus fuses with a tritium nucleus to produce a helium nucleus and a neutron.
Why does fusion require extremely hot, dense environments, such as the core of a star?
Fusing nuclei must have high kinetic energy to overcome the electrostatic repulsion between positively charged protons; this is only achieved in extremely hot and dense environments.
When two hydrogen nuclei fuse to form deuterium, a .......... and an electron neutrino are also produced, as one proton converts into a neutron by beta-plus decay.
When two hydrogen nuclei fuse to form deuterium, a positron and an electron neutrino are also produced, as one proton converts into a neutron by beta-plus decay.
True or False?
In the centres of stars, four helium nuclei fuse together to produce one hydrogen nucleus.
False.
It is the reverse: four hydrogen nuclei fuse to produce one helium nucleus, releasing energy that fuels the star.
Why is energy released during a fusion reaction?
The mass of the new, heavier nucleus is less than the total mass of the original nuclei; this mass difference is converted into energy, and the binding energy per nucleon increases.
What do nuclear equations represent, and what other type of equation are they similar to?
Nuclear equations represent nuclear reactions, such as fission and fusion; they are similar to chemical equations in Chemistry.
What two quantities must balance on either side of a nuclear equation?
The nucleon numbers (top numbers) and the proton numbers (bottom numbers) must each balance on both sides.
In a nuclear equation, the sum of the .......... numbers (top numbers) must be equal on both sides of the equation.
In a nuclear equation, the sum of the nucleon numbers (top numbers) must be equal on both sides of the equation.
When a uranium-235 nucleus is struck by a neutron and undergoes fission into strontium and xenon nuclei, what else is released?
Two neutrons are released, along with energy.
How can balancing a nuclear equation be used to find an unknown quantity, such as the number of neutrons released in a reaction?
By ensuring the total nucleon number and proton number are equal on both sides, any unknown coefficient (e.g. the number of neutrons emitted) can be calculated.
True or False?
Only the nucleon (top) numbers need to balance in a nuclear equation; the proton (bottom) numbers do not need to.
False.
Both the nucleon numbers and the proton numbers must balance on each side of a nuclear equation.

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