P6 | radioactivity

Question 1

why is alpha radiation highly ionising? why is it dangerous if inhaled?

Answer 1

they have a 2+ charge (helium nucleus has 2 protons) meaning they can ionise very easily

they can easily damage/ionise our cells

Question 2

why is alpha radiation lowly penetrative?

Answer 2

they have 2 protons meaning they are heavy, meaning they lose their energy very quickly in air and can’t travel far

Question 3

why is gamma radiation lowly ionising?

Answer 3

they have no charge meaning they are very weak ionisers

Question 4

why is gamma radiation very penetrative?

Answer 4

gamma radiation is energy; high energy and high frequency travelling at the speed of light, making them very penetrative and able to travel very far

Question 5

which part of a power station provides thermal energy from a chain reaction?

Answer 5

nuclear reactor

Question 6

which part of a power station transfers kinetic energy into electrical energy?

Answer 6

generator

Question 7

how do control rods reduce the number of nuclear reactions in a reactor?

Answer 7

• control rods can be moved in and out
• absorb excess neutrons
• meaning fewer neutrons left to cause fission

Question 8

why is nuclear fusion important to life on earth?

Answer 8

nuclear fusion occurs in the sun which provides energy needed for life on earth

Question 9

how do moderators control the nuclear reactions in a reactor?

Answer 9

moderators slow down neutrons in order for them to be absorbed by/collide with unstable nuclei

Question 10

how can the thermal energy released by fission/fusion be converted into electrical energy in a power station?

Answer 10

• thermal energy is used to boil water to create steam
• this steam is used to drive the turbine
• the turbine is used to turn the generator

Question 11

what is radioactive decay?

Answer 11

the random, spontaneous breakdown of an unstable nucleus resulting in the release of energy and matter from the nucleus

Question 12

what is background radiation?

Answer 12

radiation that is always present

Question 13

sources of background radiation

Answer 13

• medical sources
• food and drink
• gamma rays from rocks
• radon gas from ground
• nuclear power and testing
• cosmic rays

Question 14

why is radon gas dangerous and how can it be removed?

Answer 14

• colourless and odourless
• when inhaled, alpha radiation from radon can damage cells which can cause cancer
• can be prevented by installing pumps into buildings to remove the gas

Question 15

what is cosmic (microwave) background radiation?

Answer 15

radiation from space that is always present; produced during the Big Bang; leftover energy from the initial explosion

Question 16

describe how a teacher should use a Geiger-Müller (GM) tube to compare the count-rates from two different radioactive rocks

Answer 16

1. put rocks near/in front of the GM tube
2. measure the count rates separately for each rock for the same time period
3. keep the distance between the GM tube and rock the same for both rocks
4. take background radiation into account
5. repeats the readings and take averages

Question 17

how were electrons distributed in the plum pudding model?

Answer 17

electrons are randomly distributed in a sphere of positive charge

Question 18

what did the gold foil experiment conclude?

Answer 18

a majority of alpha particles went straight through = most of an atom is empty space

some alpha particles deflected slightly = atoms have a positively charged nucleus which repels positive alpha particles

very few alpha particles completely deflected/did not pass through = the nucleus (mass) is very small and in the centre of the atom

Question 19

why was the plum pudding model scrapped?

Answer 19

the new experimental evidence from the gold foil experiment didn’t support the plum pudding model

the plum pudding model could not explain why some alpha particles were deflected backwards

Question 20

what was Bohr’s nuclear model?

Answer 20

• a tiny central positively charged nucleus in the center which contains most of the atom’s mass
• most of the atom is empty space
• electrons are in fixed orbits called energy levels/electron shells

Question 21

process of beta minus decay

Answer 21

• a neutron becomes a proton and an electron
• mass number doesn’t change because even though a neutron has been lost, a proton has been gained
• atomic number increases by one because a proton is gained

Question 22

process of beta plus decay

Answer 22

• a proton becomes a neutron and a positron
• mass number doesn’t change because a neutron is gained
• atomic number decreases by one because a proton has been lost

Question 23

radiations

Answer 23

α⁴₂ = alpha

β⁰₋₁ = beta minus

β⁰₁ = beta plus / positron

γ⁰₀ = gamma