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Physics > RadioactiviTEA > Flashcards

RadioactiviTEA Flashcards

Nuclear fission/fusion, Energy of nuclear reactions, Binding Energy (per nucleon), Mass defect and their implications

1
Q

What is mass defect ?

A

The difference between the actual mass of a nuclide and the masses of its constituent nucleons when taken apart

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2
Q

What mass is always higher

between nuclide mass and total constituent mass?

A

Total constituent mass

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3
Q

True or False?

The higher the (potential) energy state of a substance, the higher its mass

A

True

These changes are just so minute in everyday circumstances that they are considered negligible, however, such is not the case in nuclear physics

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4
Q

What is Einstein’s mass-energy equation?

A

ΔΣ = Δmc2

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5
Q

What is seen as the energy equivalent of the mass defect?

A

Binding Energy

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6
Q

True or False?

In Nuclear physics there are large changes in energy which result to small changes in mass

A

False

There are considerable and visible changes in mass due to the large energy changes in Nuclear Physics

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7
Q

What is the rest mass of a particle

A

The mass of a particle when it is stationary

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8
Q

What is the (unified) atomic mass unit (U)?

A

The mass of 1/12th the mass of the C-12 isotope

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9
Q

What is the value of 1 (unified) atomic mass unit (U) in kilograms?

A

1U = 1.66 x 10 -27 kg

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10
Q

What is the value of 1 (unified) atomic mass unit (U) in MeV (mega electron volts)?

A

1U = 931.5 MeV

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11
Q

What does the mass defect imply?

A

That energy is released when the nucleons are combined to form the nuclide

This same energy will be released when the nuclide is separated into its nucleons

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12
Q

How does binding energy determine nuclide stability?

A

The higher the binding energy per nucleon, the more stable the nuclide

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13
Q

What is binding energy?

A

This is the minimum energy required to split a nuclide into its constituent nucleons

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14
Q

What is binding energy per nucleon?

A

This is the binding energy of a nuclide divided by the nucleon number

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15
Q

What is the nature of strong nuclear force between nucleons in the nucleus of an atom?

A

It is attractive and very short-ranged.

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16
Q

What are nucleons?

A

Particles that make up a nucleus/nuclide

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17
Q

Name the two types of nucleons in a nuclide

A

Protons and Neutrons

18
Q

What is there to note about beta (electron, β-) radioactive decay?

A

The proton number increases when the electron is liberated

19
Q

What is there to note about beta (positron, β+) radioactive decay?

A

The proton number decreases when the positron is liberated

20
Q

What is there to note about alpha (α) radioactive decay?

A

Nucleon number decreases by 4 and proton number decreases by 2 when the alpha particle is liberated

21
Q

What is there to note about gamma (γ) radioactive decay?

A

There is no change in either the nucleon number or the proton number, only energy is released (making the nuclide more stable) when a gamma ray is emitted

22
Q

What is noticed when attempting to balance masses in a nuclear equation?

A

There is typically a lesser mass on the right hand side of the equation

23
Q

What reason can be given for the difference in masses on either side of a nuclear equation?

A

Energy is released when the reaction occurs

24
Q

In what form is this energy typically released?

A

Kinetic energy

25
Q

What does this kinetic energy typically do when released?

A

It is supplied to the particles of the system

26
Q

What is the point of Albert Einstein’s mass-energy equation?

A

To explain/ try to quantify the mass lost due to large energy changes

Footnote: Objects at different energies always have different masses, with objects at higher energies having higher masses. In real life, the energy changes are too small to be accounted for, but they always occur

27
Q

In what context is binding energy more adequately defined?

A

Externally. Binding energy is the minimum external energy needed to separate a nuclide into its constituent nucleons

28
Q

At what speed should neutrons be to induce fission?

A

Low speeds

Slow-moving or thermal neutrons are the most effective at inducing fission

29
Q

What does it mean when a nuclide is described as ‘fissile’?

A

The nuclide is capable of undergoing nuclear fission

In neutron-induced fission, the neutron’s introduction to the already fissile nuclide makes it more unstable, initiating a fission that’d have otherwise happened at a later date

30
Q

What is the function of a moderator in a nuclear reactor?

A

It reduces the speed of the fast-moving neutrons produced

31
Q

Give an example of two materials that can be used as a moderator in a nuclear reactor?

A

Carbon (Graphite) rods or Water

32
Q

What type of materials are moderators made of:

Good or Poor absorbers of neutrons?

A

Poor absorbers of neutrons

33
Q

What type of materials are control rods made of:

Good or Poor absorbers of neutrons?

A

Good absorbers of neutrons

These materials absorb these neutrons without becoming unstable themselves. They are non-fissile materials

34
Q

What is the function of the control rods in a nuclear reactor?

A

They absorb (excess) neutrons produced in the nuclear reactor

This helps to regulate the rate of fission

35
Q

Give an example of two materials that can be used as a control rod in a nuclear reactor?

A

Boron or Cadmium rods

36
Q

How can a nuclear reaction be stopped in a nuclear reactor?

A

By fully lowering down the control rods within the reactor

37
Q

Give an example of materials that can be used as coolants in a nuclear reactor?

A

Water, Deuterium Oxide (Heavy water), or Liquid Sodium

38
Q

Give a reason why water is an effective coolant in a nuclear reactor?

A

It has a very high specific heat capacity

This makes it capable of transferring very high amounts of thermal energy

39
Q

What is the decay constant of a radioactive substance?

A

This is the probability that a radioactive nuclide will decay per unit time

40
Q

What is the activity of a radioactive substance?

A

This is the amount of a radioactive substance decaying per unit time

It is the rate of disintegration of a radioactive specimen

41
Q

Why is radioactive decay spontaneous?

A

Because one can never determine which nuclide within a radioactive specimen that will decay next

42
Q

Why is radioactive decay random?

A

Because it is not affected by physical and chemical factors

Such as temperature, pressure and concentration (the presence of other nuclides around it)

Physics (3 decks)

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