Radioactivity

Question 1

Spontaneous

Answer 1

The decay cannot be induced and occurs without external influence

Question 2

Random nature of decay

Answer 2

Cannot be predicted which nuclei will decay and when

Question 3

Activity

Answer 3

The number of decays per unit time

Question 4

Decay constant

Answer 4

The probability that a decay will occur

Question 5

Isotopes

Answer 5

Nuclei with the same proton number but different nucleon numbers

Question 6

What occurs during beta minus decay

Answer 6

A neutron turns into a proton meaning a down quark changes to an up quark
An electron and antineutrino are given off

Question 7

Binding energy

Answer 7

The minimum energy required to separate all the nucleons in a nucleus

Question 8

Explain binding energy

Answer 8

Mass if nucleus is less than the mass of nucleons
Difference in mass is mass defect
Energy must be supplied to separate the nucleons
The energy is called binding energy

Question 9

Explain the energy release in nuclear reactions

Answer 9

The mass decreases
Mass has been converted to energy
The energy released ise=mc^2

Question 10

Explain induced nuclear fission

Answer 10

A slow moving neutron is absorbed by a nucleus
The nucleus splits into two smaller nuclei and fast protons
Energy is releases at kinetic

Question 11

Nuclear chain reaction

Answer 11

Neutrons are produced by each fission of a uranium nucleus
Neutrons are absorbed by other uranium nuclei
Causing further fission reactions

Question 12

Compare fissions reactions and radioactive decay

Answer 12

Similarities
Both give off radiation
Both release energy and lose mass
Differences
In fission two fragments of similar sizes are made
In fission neutrons cause chain reactions
Fission can be induced radioactive decay is spontaneous

Question 13

How do fission power stations work?

Answer 13

Fission reactor generate energy from kinetic energy of fragments
Nuclei collide transferring kinetic to thermal energy
Temperature of uranium increases
Coolant carries thermal energy away from the reactor core
That energy heat water to steam
Steam drives turbines which are linked to generators

Question 14

Fuel rods

Answer 14

Contain uranium nuclei for reactions

Question 15

What are moderators and what do they do

Answer 15

Graphite or water
Slow down the fast moving neutrons because slow moving neutrons have more chance of causing fission

Neutrons collide with nuclei of the moderator
Causing a transfer of kinetic energy

Question 16

What are control rods

Answer 16

Made from boron to absorb neutrons so one neutrons survives between successive collisons

Question 17

Environmental effects of nuclear waste

Answer 17

Nuclear waste includes the daughter nuclei and last for a long time
Cause ionisation and mutation of DNA in living things

Question 18

What is nuclear fusion

Answer 18

The joining together of light nuclei to make heavier nuclei
Mass decreases in the reaction
The lost mass is transformed to energy
Kinetic energy is given off and sometimes gamma rays

Question 19

What are the conditions for nuclear fusion

Answer 19

Positively charge nuclei repel so they need to be close to eachother for the strong nuclear force to take affect
High kinetic energy is needed for this to occur so high temperatures are needed

Question 20

Nuclear fusion in stars

Answer 20

Very high temperatures mean that nuclei have lots of kinetic energy
High pressure and density mean there are very frequent collisons
Hydrogen nuclei form helium nuclei

Question 21

How do fusion reactions occur at low temperatures

Answer 21

Nuclei have a range of kinetic energies

Some have a higher energy than the average

Question 22

Radioactive decay is

Answer 22

Spontaneous and random