Unit 2 - Particles

Question 1

when does radioactive decay occur?

Answer 1

when an unstable nucleus makes an attempt to become more stable.

Question 2

what is Alpha decay (α)?

Answer 2

in this decay an alpha particle is emitted by the nucleus. An alpha particle is emitted by the nucleus consists of two protons and two neutrons (i.e. A helium nucleus).

Question 3

what must be conserved when doing nuclear equations?

Answer 3

mass number and atomic number

Question 4

what is Beta decay (β)?

Answer 4

takes place when a neutron in the nucleus decays into a proton and an electron The proton stays in the nucleus (so the atomic number increases by 1) while the electron is ejected from the atom’s nucleus as a beta particle.

Question 5

what is Gamma decay (γ)?

Answer 5

Gamma rays are photons of electromagnetic energy; they are not particles. gamma rays are ejected from an atom’s nucleus

Question 6

what are the two key processes which can result in the production of energy from the nucleus?

Answer 6

fission and fusion

Question 7

define fission

Answer 7

a large atomic nucleus splits into 2 smaller nuclei and sometimes several neutrons. The smaller nuclei and neutrons that are produced gain large amounts of kinetic energy

Question 8

what is fission simulated by Neutron Bombardment?

Answer 8

A neutron is “fired” at a uranium nucleus, causing the uranium nucleus to split. Smaller Daughter particles are produces as well as 3 further neutrons, all of which have a great deal of kinetic energy.

Question 9

how can a fission reaction overheat?

Answer 9

One reaction produces several neutrons which can go on to cause further fission reactions. Left uncontrolled this leads to an ever escalating set of chain reactions and the reactor will eventually overheat.

Question 10

how do we dispose of daughter particles from nuclear fission?

Answer 10

by burying it in shielded containers.

Question 11

define nuclear fusion

Answer 11

2 small atomic nuclei combine to form a larger nucleus. Other small particles (such as neutrons) may also be left over.

Question 12

where does nuclear fusion take place?

Answer 12

in stars like the sun

Question 13

what are the conditions required for nuclear fusion to occur?

Answer 13

• High pressure (particles are closer together)
• High temperature (particles move faster)
Both of these increase the likelihood of collisions and therefore successful reactions.

Question 14

what is plasma?

Answer 14

Under these high temperatures in fusion the electrons dissociate from their parent nuclei, leaving a mixture of highly charged particles

Question 15

how is plasma controlled?

Answer 15

Powerful magnetic fields are used to control the path of the charged plasma. The fields can also be used to compress the gas,

Question 16

why is mass lost in nuclear fission/fusion and how can this be calculated?

Answer 16

The “lost mass” is converted into kinetic energy of the products
E=mc2

Question 17

what is the standard model?

Answer 17

the theory of fundamental particles and how they interact. Is explains existing particles and helps predict new particles we have not discovered.

Question 18

What is antimatter?

Answer 18

Same mass but opposite charge to matter

Question 19

What happens when antiparticles meet?

Answer 19

annihilate each other and their combined mass is converted into energy (E=mc2).

Question 20

What are the two types of fundamental particles or fermions?

Answer 20

Leptons and quarks

6 types of leptons and 6 types of quarks

Question 21

What are the six leptons?

Answer 21

Generation 1 - the electron (e) and its electron neutrino (νe)
Generation 2 - the muon (μ) and its muon neutrino (νμ)
Generation 3 - the tauon (τ) and its tauon neutrino (ντ)

Question 22

Where are each generation of leptons found?

Answer 22

Generation 1 particles are found in ordinary matter, but generation 2 and 3 particles are mainly found in cosmic rays and particle accelerators.

Question 23

What are quarks?

Answer 23

Quarks fall into the three generations and have not been found to exist on their own. Quarks only exist in bound states. Quarks have fractions of charges and must combine with others to form other particles with charge 1, a multiple or zero

Question 24

What are the six quarks?

Answer 24

Generation 1 - the up (u) and the down (d) quarks
Generation 2 - the charm (c) and the strange (s) quarks
Generation 3 - the top (t) and the bottom (b) quarks

Question 25

What charge does each quark have?

Answer 25

The up, charm and top all have a charge of +2/3. The down, strange and bottom all have a charge of -1/3.

Question 26

Where are each generation of quarks found?

Answer 26

Only up and down quarks are found in ordinary matter. The other quarks are made in particle accelerators and may also exist in stars.

Question 27

What are hadrons?

Answer 27

composite particles (particles made up of other particles). They are particles made from quarks

Question 28

What are baryons?

Answer 28

Made from three quarks or three antiquarks

Question 29

What are mesons?

Answer 29

Made of a quark and an antiquark

Question 30

What charge must composite particles have?

Answer 30

A whole charge e.g. -2e,+1e

Question 31

What are force mediating particles?

Answer 31

bosons: photons (electromagnetic force), W- and Z-bosons (weak force), and gluons (strong force).

Question 32

What does beta decay provide evidence for?

Answer 32

The existence of the neutrino