chapter 26 - Nuclear physics (scuffed quizlet)

Question 1

Einsteins equation

Answer 1

E=mc^2

Question 2

The two interpretations of Einsteins equation

Answer 2

mass is a form of energy

energy has mass

Question 3

Explanation of the first interpretation of Einsteins equation that mass is a form of energy

Answer 3

the interaction of an electron-positron pair illustrates how these two particles completely destroy each other (annihilation) and the entire mass of the particles is transformed into two gamma photons.

Question 4

Explanation of the second interpretation of Einstein’s equation that energy has mass

Answer 4

the change in mass of an object is related to the change in energy by the equation ΔE=Δmc^2 - a moving ball has kinetic energy implying that its mass is greater than its rest mass.
or more simply, a mug of hot tea will decrease in mass as it cools but by an almost negligible amount.

Question 5

Equation to calculate change in mass of a moving everyday object

Answer 5

Δm = 1/2 mv^2 / c^2

Question 6

What event can not be explained by the conservation of energy theory

Answer 6

In alpha decay, the parent nucleus emits an alpha particle, creating a daughter nucleus, which recoils in the opposite direction. Both the alpha particle and daughter nucleus have kinetic energy.

Question 7

How to explain alpha decay with the conservation of mass-energy

Answer 7

the total amount of mass and energy in a system is conserved. Since energy is released in radioactive decay there must be an accompanying decrease in mass. This means the total mass of the alpha particle and the daughter nucleus must be less than the mass of the parent nucleus - said decrease in mass is equivalent to the energy released.

Question 8

How does a pet scan use annihilation

Answer 8

when a positron and electron see they annihilate each other and their entire mass is transformed into energy in the form of two identical gamma photons- the point of annihilation can be calculated

Question 9

What occurs in pair production

Answer 9

a single photon vanishes and its energy creates a particle and corresponding antiparticle.

Question 10

An increase in mass multiplied by c^2 must be …

Answer 10

equal to the minimum kinetic energy of the colliding particles

Question 11

What is deuterium

Answer 11

an isotope of hydrogen

Question 12

what is in the nucleus of deuterium

Answer 12

one proton and one neutron

Question 13

According to Einsteins equation, what happens to the mass of nucleons separated from the deuterium nucleus

Answer 13

when the proton and neutron are separated their total mass when separated must be greater than the mass of the deuterium nucleus

Question 14

What is the mass defect

Answer 14

the difference between the mass of the completely separated nucleons and the mass of the nucleus

Question 15

What is the binding energy

Answer 15

the minimum energy required to completely separate a nucleus into its constituent protons and neutrons

Question 16

How to calculate the binding energy of a nucleus

Answer 16

mass defect of nucleus x c^2

Question 17

Larger nuclei have

this one is dumb, but ok

Answer 17

larger binding energies

Question 18

How do we compare how easy it is to break up nuclei

Answer 18

determine the average binding energy per nucleon

Question 19

The higher the binding energy per nucleon…

Answer 19

the more tightly bound the nucleons are - meaning the nucleus is more stable

Question 20

What are thermal neutrons

Answer 20

neutrons with mean kinetic energy similar to the thermal energy of particles in a nuclear reactor core.

Question 21

What is induced fission

Answer 21

where a stable atom’s nucleus absorbs a neutron making it unstable and fissions into two lighter elements

Question 22

The energy released in a fission reaction is…

Answer 22

the difference between the total binding energies before and after fission

Question 23

The energy released in a single fission reaction is a combination of…

Answer 23

kinetic energy of the particles produced and the energy of photons and neutrinos emitted

Question 24

How is the steady production of power from a nuclear reactor controlled

Answer 24

by ensuring that on average one slow neutron survives between successive fission reactions.

Question 25

Key components of a fission reactor

Answer 25

Fuel rods are spaced evenly within a steel-concrete vessel known as a reactor core.
A coolant is used to remove the thermal energy produced from the fission reaction within the fissile fuel.
The fuel rods are surrounded by the moderator and controls rods can be moved in and out of the core.

Question 26

What are fuel rods

Answer 26

they contain enriched uranium which consists mainly of uranium-238 with 2-3% uranium-235

Question 27

What is the moderator in a nuclear fission reactor

Answer 27

a component to slow down the fast neutrons produced in fission reactions to increase the likelihood on the uranium nuclei absorbing the neutrons. In many reactors the moderator and coolant are the same

Question 28

The material of the moderator must be…

Answer 28

cheap and readily available and must not absorb the neutrons in the reactor

Question 29

Mean kinetic energy of thermal neutrons

Answer 29

3/2kT
(K= boltzmann Constant)
(T= temp in kelvin)

Question 30

What are control rods

Answer 30

made of a material whose nuclei readily absorb neutrons. The position of the control rods is automatically adjusted to ensure that exactly one slow neutron survives per fission reaction. They can be pushed further into the reactor core to completely stop the fission reaction.

Question 31

Environmental impacts of nuclear fission reactors

Answer 31

Neutrons of intermediate kinetic energies are absorbed by uranium-238 nuclei within the fuel rods which quickly decay into plutonium-239 ehich is one of the most hazardous materials produced.
Radioactive waste is hard to dispose of and can have extremely long half-lives

Question 32

What is Nuclear fusion

Answer 32

a process where small nucleus are combined to make larger nuclei producing enormous amounts of energy

Question 33

The only way to make nuclei fuse is to …

Answer 33

bring them close together within a few 10^-15 m of each other so that short-range strong nuclear forces can attract them into a larger nucleus

Question 34

Conditions for nuclear fusion

Answer 34

high temperature and high pressure from high density

Question 35

proton-proton cycle or hydrogen-burning cycle.

Answer 35

Two protons fuse together to produce a deuterium nucleus, a positron and neutrino to produce 2.2Mev of energy. The two single protons have 0 binding energy and the deuterium nucleus has a binding energy of 2.2Mev (the difference is the energy released in the reaction). The deuterium fuses with a proton to make a helium-3 nuclei and 5.5Mev of energy. The helium-3 combines with another helium-3 to form a helium-4 and two protons and 12.9MeV of energy.

Question 36

How many times does the proton-proton fusion reaction occur in the sun

Answer 36

9x10^37 times a second

Question 37

Why are there no fusion reactors yet

Answer 37

it is difficult to maintain high temperatures for long enough to sustain fusion and on confining the extremely hot fuel within a reaction.