6.4 Nuclear

Question 1

Alpha particle scattering experiment and what it proved

Answer 1

A stream of alpha particles were emitted at a piece of gold foil. Most of the particles went straight through, but some were reflected back. This meant that matter must be mostly empty space with small, dense positively charged pockets (the nucleus)

Question 2

fm

Answer 2

femtometer - 10-15m

Question 3

Standard notation for an atom

Answer 3

AZX

Where

A is mass number

Z is proton numbe

Question 4

Strong nuclear force

Answer 4

The force that holds the nucleus together against the repulsion of the electrostatic repulsion

Question 5

How the strong force varies with distance

Answer 5

Repulsive < 0.5 fm

Attractive enough to overcome electrostatic repulsion at < 3 fm

Question 6

Hadron

Answer 6

Particles that feel the strong nuclear force (made of quarks)

Question 7

What is the only stable hadron

Answer 7

Proton

Question 8

Lepton

Answer 8

Fundamental particles that don’t feel the strong force but do feel the weak nuclear force

Question 9

Examples of hadrons (2)

Answer 9

proton, neutron

Question 10

Examples of leptons (2)

Answer 10

Electron, neutrino

Question 11

Antiparticle and its properties

Answer 11

Every particle has an antiparticle with the same properties, except it will have the opposite charge

Question 12

Pair production

Answer 12

When energy is transformed into a particle and an antiparticle

Question 13

How a gamma ray might create antimatter

Answer 13

A high energy photon can turn into a electron and a positron via pair production. The energy of the photon (hf) is transformed into the mass of the two produced particles (leftover energy is put to their kinetic energy)

Question 14

Annihilation

Answer 14

When a particle meets its antiparticle the mass of both is converted into energy in the form of two photons

Question 15

Quark

Answer 15

The building block of hadrons

Question 16

Quark composition of a proton

Answer 16

uud

Question 17

Quark composition of a neutron

Answer 17

udd

Question 18

up quark charge

Answer 18

+2/3

Question 19

down quark charge

Answer 19

-1/3

Question 20

strange quark charge

Answer 20

-1/3

Question 21

β- decay

Answer 21

Occurs in a neutron rich atom. Neutron decays to a proton, electron and antineutrino. (d –> u)

Question 22

β+ decay

Answer 22

Occurs in a proton rich atom. Proton changes into a neutron and emits a positron and a neutrino, (u–>d)

Question 23

Radioactive decay

Answer 23

When a nucleus stabilises by releasing particles/energy in various forms

Question 24

Properties of radioactive decay

Answer 24

It is spontaneous and random

Question 25

What is meant by spontaneous and random

Answer 25

There is no way to know when a nucleus will decay. It can't be predicted

Question 26

Alpha radiation

Answer 26

A helium nucleus

Question 27

β radiation

Answer 27

An electron

Question 28

γ radiation

Answer 28

A gamma ray

Question 29

ν (nu)

Answer 29

Symbol for neutrino

Question 30

Range of β+ radiation

Answer 30

Effectively 0 since it will almost instantly be annihilated by an electron

Question 31

How to investigate radioactivity

Answer 31

Place a material between a radioactive source and a geiger-muller tube and record the count rate over a period of time. Repeat with different materials

Question 32

where α emmision occurs

Answer 32

Heavy nuclei

Question 33

when γ radiation is emitted

Answer 33

When a nucleus has too much energy (often after alpha or beta decay)

Question 34

Activity

Answer 34

The number of nuclei that decay each second

Question 35

Decay constant

Answer 35

The number of nuclei that decay each second

Question 36

Equation for activity

Answer 36

decay constant * undecayed nuclei

Question 37

Half life

Answer 37

The average time taken for half of the undecayed nuclei to decay

Question 38

Experiment to determine half life of an isotope

Answer 38

Calculate the background radiation rate first using a geiger-muller counter. Fill a bottle with uraniuam salt and protactinium-234. Shake the bottle so they mix and then wait for them to seperate again. Once they have seperated take measurements by measuring the count for 10 seconds. Repeat this measurement every say 30 seconds. Plot a graph and determine half life from it

Question 39

Equations for half life, nuclei and activity

Answer 39

Just use common sense exponential maths

Question 40

How carbon dating works

Answer 40

Living things take in carbon-14 from the atmosphere and all living things will have the same ratio of carbon-12 to carbon-14. When something dies the carbon-14 decays and is not replenished so the ratio will start to decrease. Therefore how long ago something died (e.g. paper from wood) can be determined. The half life of carbon-14 is about 6000 years so it is not suitable for very long ago (e.g. dinosaurs like if u wanted to know when a stegosaurous died or something like that maybe a pterodactyl idk)

Question 41

Mass defect

Answer 41

The difference in mass between a nucleus and the sum of the masses of all its protons and neutrons if they were separated

Question 42

Binding energy

Answer 42

Equals the mass defect (E=mc2)

Question 43

Graph of binding energy per nucleon against nucleon numbner

Answer 43

Goes up steeply then peaks and slowly decreases. Peaks at Iron

Question 44

How to calculate energy released from a fission/fusion reaction

Answer 44

It is equal to the change in binding energy

Question 45

How fission reactors work

Answer 45

Rods of uranium rich in 235U undergo nuclear fission, producing energy and emitting high energy neutrons. These neutrons go on to collide with other uranium atoms causing them to undergo fission and so on, in a chain reaction. The emitted neutrons are travelling to fast to cause fission so they are slowed down by a moderator such as water. To make sure that the chain reaction remains steady and does not get out of control, control rods made of boron are lowered into the case. These absorb some of the neutrons so that there are not enough to cause the reaction to get out of control. The heat from the reaction is then used to heat water and make steam, which powers a turbine and then a generator

Question 46

Environmental impact of nuclear waste

Answer 46

Radioactive waste can take a long time to decay to safe levels Natural distasters pose a risk to nuclear plants (e.g. Fukishima)

Question 47

How nuclear fusion reactions work

Answer 47

Light nuclei under very high temperatures (much higher than in fission) combine and form a heavier nucleus and release lots of energy