Nuclear

Question 1

What is the binding energy of free neutrons?

Answer 1

No binding energy for free neutrons or protons

Question 2

Binding energy increases

Answer 2

During fission and fusion reactions

Question 3

Explain the correletation between collisions of neutrons on a moderator and the nucleon number of the moderator atoms

Answer 3

During a collision between a neutron and a moderator atom, kinetic energy is lost.

If the nucleon number of the moderator atoms is high then not much Kinetic energy is lost, this means more collisions are needed.

More kinetic energy is lost when the nucleon number of the moderator atoms are close to that of the neutron.

Question 4

Three benefits of using nuclear power

Answer 4

Some nuclear power stations can adjust their output quickly (boron control rods)

Nuclear power can be produces continuosly without the dependence of weather conditions

Little greenhouse gas emissions

Question 5

State what happens to a neutron incident on the moderator

Answer 5

A neutron collides elastically with the moderator and loses some of its kinetic energy

Question 6

Sources of Nuclear Waste

Answer 6

The most dangerous nuclear waste are the fission fragments

Spent fuel rods left over with radioactive isotopes

Question 7

How the nuclear waste is treated?

Answer 7

The nuclear waste is intially placed in cooling ponds underwater.

The plutonium and uranium is separated to be recycled

High level waste is vitrified into pyrex glass and then places in concrete bunkers to be stored deep underground.

Question 8

Problems and solutions with nuclear waste

Answer 8

The waste is intially very hot so it has to be cooled by being placed in water pools

In liquid form the high level of waste may leak hency the need to vitrify the nuclear waste

The waste will be radioactive for thousands of years due to a large half life, therefore it needs to be stored in geologically stable areas

Question 9

Why are low nucleon atoms stable?

Answer 9

The strong nuclear force acts between all nucleons. This force is stronger than electrostatic repulsion

Question 10

Why do bigger nuclei have more neutrons?

Answer 10

The neutrons help to spread the protons away from each other to reduce electromagnetic repulsion. When there are more protons, electromagnetic repulsion increases, therefore more neutrons are needed to reduce the repulsion.

Question 11

Cloud chamber observations

Answer 11

Alpha particles produce straight lines and they are all the same length

Beta particles produce wispy tracks that are easily deflected as a result of collisions with air molecules. These tracks are less visible as they are less ionising

Question 12

Activity Bq or s^-1

Answer 12

the number of nuclei of an isotope which disintegrate per second

Question 13

Random nature of radioactive decay

Answer 13

Every nucleus of a radioactive isotope has an equal probability of undergoing radioactive decay

Question 14

The decay constant

Answer 14

The decay constant is the probability of an individual nucleus decaying per second

Question 15

Caron dating

Answer 15

• carbon-14 isotope in living plants
• it has a half life of 5500 years
• this means there is negligible decay during a plants lifetime
• when the plant dies it doesnt taken in any carbon-14
• age can be calculated from activity

Question 16

Radioactive tracers

Answer 16

• need a half life which is long enough for an operation or scan but short enough to decay quickly after use
• emit beta or gamma radiation so it can be detected outside the body without causing harm

Question 17

N-Z graph

Answer 17

N=Z is the line of stability

For light isotopes ( Z < 20 ) the stable nuclei follow the NZ line

As Z increases beyond 20 - stable nuclei have more neutrons than protons

Question 18

Alpha emitters

Answer 18

Are situated above the stable atoms and occur when Z > 60

the strong nuclear force is unable to overcome the electrostatic force of attraction between protons

Question 19

B- emitters

Answer 19

they are situated to the left of the stable nuclei where the isotopes are neutron rich

Question 20

B+ emitters

Answer 20

They occur to the right of the stability belt. This is where the isotopes are proton rich

Question 21

Metastable state

Answer 21

an excited state of the nuclei of an isotope that lasts long enough after alpha or beta emission for the isotope to be separated from the parent isotope

Question 22

Nuclear radius and debroglie wavelength of electron diffraction

Answer 22

Rsinθmin = 0.61λ

Question 23

R0

Answer 23

1.05 Fm

Question 24

Technetium-99 m

Answer 24

used to monitor blood flow

Question 25

Plotting R against A^1/3

Answer 25

Gradient is equal to r0 and it goes through the origin

Question 26

Plotting Ln R against LnA

Answer 26

Gives the gradient as 1/3 and the y intercept is Ln r0

Question 27

Nuclear density

Answer 27

Assuming the nucleus is spheical

Nuclear volume is proportional to the mass of the nucleus

Therefore nuclear density is constant

Question 28

Binding energy

Answer 28

The binding energy of the nucleus is the work that must be done to separate nucleus into its constituent neutrons and protons

Question 29

Binding energy explained

Answer 29

When a nucleus is formed, energy is released as the strong nuclear force does work pulling the nucleons together. This energy released is equal to the binding energy. This means the mass of the nucleus is less.

Question 30

Binding energy and mass defect

Answer 30

the binding energy is the same as the energy during mass defect calculation

Question 31

Nuclear Stability

Answer 31

• The binding energy of each nuclide is different

Question 32

Binding energy per nucleon

Answer 32

A nuclide with a greater binding energy per nucleon is more stable

Question 33

Nuclear fusion

Answer 33

The product nucleus has more binding energy per nucleon