Physics 9

Question 1

Draw and label an atom.
Include the three components that an atom is made of.
What is the charge of each of these particles?

Answer 1

Protons - positive
Neutrons - neutral
Electrons - negative

Question 2

Define nuclear radiation.

Answer 2

The energy carried by particles from a radioactive substance or spreading out from a source.

Question 3

Name some sources of background radiation.

Answer 3

Cosmic/sun’s rays
Nuclear disasters/accidents
Natural sources such as rocks (e.g. granite)

Question 4

Describe the structure of α radiation. Include its symbol.

Answer 4

2 protons, 2 neutrons (the same as a helium nucleus)
4
α
2

Question 5

Describe the structure of β radiation. Include its symbol.

Answer 5

A single electron
0
β
-1

Question 6

Describe the structure of γ radiation. Include its symbol.

Answer 6

An electromagnetic wave (photon)
0
γ
0

Question 7

Define half-life.

Answer 7

Half-life is the time it takes for half of the unstable nuclei in a sample to decay
For the activity of the sample to halve
For the count rate to halve.

Question 8

Explain how Rutherford and Marsden discovered the structure of the atom.

Answer 8

A beam of alpha particles was aimed at very thin gold foil and their passage through the foil detected. The scientists expected the alpha particles to pass straight through the foil but something else also happened.
Some of the alpha particles emerged from the foil at different angles and some even came straight back. The scientists realised that the positively charged alpha particles were being repelled and deflected by a tiny concentration of positive charge in the atom. As a result of this experiment, the plum pudding model was replaced by the nuclear model of the atom.

Question 9

What is an isotope?

Answer 9

Atoms of an element with the same number of protons and electrons but different numbers of neutrons.

Question 10

What are the three types of nuclear radiation? Order them from least penetrating to most penetrating.

Answer 10

α alpha
β beta
γ gamma

Question 11

What is meant by the term “ionising radiation”?

Answer 11

Ionising radiation turns atoms into ions causing molecules to break up. The change in molecules can change DNA in the cell’s nucleus. If the DNA is sufficiently damaged, this may destroy the cell. Changes in the DNA can also cause mutations to genes that can cause cancer.

Question 12

What do the numbers represent?

4
He
Helium
2

Answer 12

4: Atomic mass (nucleus, number of protons + number of neutrons)
2: Atomic number (number of protons)

Question 13

How can we find out the number of electrons in an atom?

Answer 13

By looking at the number of protons.

number of protons = number of electrons

Question 14

What is the symbol for a neutron? What is a neutron made of?

Answer 14

1
n
0

Question 15

Do some decay equations.

Answer 15

Sketch the shape of a half-life graph.

Question 16

Explain contamination.

Answer 16

When unwanted radioactive isotopes end up on other materials, skin or clothing.

Question 17

How could we reduce levels of contamination?

Answer 17

Lead shielding (lead apron, lead wall) - gamma (most penetrating) and other radiation can be stopped by a few centimetres of lead.
Distance (radiation monitor, tongs) - keeping a person as far away as is practicable
Low exposure time (radiation monitor)

Question 18

Explain how a medical tracer works

Answer 18

A small amount of radioactive material is put into the patient’s body. The radiographer puts a detector around the body to detect any gamma rays or beta particles that pass out of the patient’s body.
Gamma rays or beta particles are used because they can pass through skin, whereas alpha particles cannot.

Question 19

Explain how x-rays work.

Answer 19

An X-ray machine produces a very concentrated beam of electrons known as X-ray photons. This beam travels through the air, comes into contact with our body tissues, and produces an image on a metal film.

Question 20

Explain radiotherapy.

Answer 20

Radioactive chemicals called tracers have chemicals that concentrate in different damaged/diseased parts of the body; the radiation concentrates it. Radiation detectors are placed outside the body to detect the radiation emitted and, with the aid of computers, build up an image of the inside of the body.

Question 21

Explain brachytherapy.

Answer 21

High doses of ionising radiation are directed at cancerous cells to kill them. There are two ways to do this:

1) From outside the body using X-rays or the radiation from radioactive cobalt
2) From inside the body by putting radioactive materials into the tumour, or close to it

Question 22

If nuclear radiation can cause harm to the body, justify why we still use it in medicine?

Answer 22

There is a way in which we can direct high doses of ionising radiation at cancerous cells to kill them. This is called radiotherapy and is a very efficient method of treating cancer patients that has been used for years.
Radioactive chemicals called tracers are also used for medical imaging. Scientists have managed to figure out what type of nuclear radiation should be used, how long we should use it for and what precautions must be taken to ensure everyone is safe.

Question 23

Complete a table on solids, liquids and gases.

Answer 23

Label the processes in a “changes of state” triangle.

Question 24

What is the density triangle? What are the units

Answer 24

/ M \
/ ρ | V \
______

density*  = kg/m³   or   g/m³
mass     = kg          or   g 
volume = m³         or   cm³*

Question 25

Compare the densities of a gas, liquid and a solid.

Answer 25

The particles in solids are very close together. They are tightly packed, giving solids high densities.
The particles in liquids are close together. Although they are randomly arranged, they are still tightly packed, giving liquids high densities. The density of a substance as a liquid is usually only slightly less than its density as a solid.
The particles in gases are very far apart, so gases have a very low density.

Question 26

Explain why evaporation has a cooling effect.

Answer 26

Evaporation is a cooling process because when a liquid turns to gas, it needs more energy, and so it has to take that energy from its surroundings. The energy is in the form of heat, and when the heat energy leaves with the evaporating liquid, the surroundings get cooler.

Question 27

Why would evaporation having a cooling effect be useful?

Answer 27

When we sweat. Our bodies are hot so our sweat absorbs energy from our skin so that it can continue to evaporate.

Question 28

Define specific heat capacity.

Answer 28

The amount of energy required to change the temperature of 1kg of substance by 1°C.

Question 29

Name four conductors.

Answer 29

Copper
Silver
Aluminium
Gold

Question 30

Name four insulators.

Answer 30

Paper
Rubber
Glass
Plastic

Question 31

What is the triangle for specific heat capacity? What do the letters stand for and what are they measured in?

Answer 31

/ ΔE \
/ m | c | Δϴ \
_________

ΔE =  change in energy:             J
m =   mass:                                  kg
c =    specific heat capacity:       J/kg°C 
Δϴ = change in temperature:    °C

Question 32

If the specific heat capacity of water is 4200J/kg°C, calculate how much energy is needed to heat 1.5kg of water from 40°C to 60°C

Answer 32

Δϴ = 60°C - 40°C = 20°C
1.5kg * 4200J/kg°C * 20°C
= 126000J

Question 33

Deine internal energy.

Answer 33

internal energy = total of random kinetic energy + potential energy
The energy stored in all materials including energy due to the motion of particles and the chemical bonds between them.

Question 34

How can we change the internal energy of a substance?

Answer 34

By heating the substance - this increases the internal energy: the movement of its particles increases,
bonds between particles break when a substance melts or evaporates, or sublimes to form a gas from a solid
By cooling the substance - this decreases the internal energy: the movement of its particles decreases,
bonds between particles form when a substance condenses or freezes, or sublimes to form a solid from a gas

Question 35

Define specific latent heat.

Answer 35

A measure of how much heat energy is needed to melt or boil a substance.

Question 36

What is the triangle for specific latent heat? What do the letters stand for and what are they measured in?

Answer 36

/ ΔE \
/ m | L \
______

ΔE = change in energy: J
m = mass: kg
L = specific latent heat: J/kg

Question 37

Name both types of latent heat.

Answer 37

Latent heat of fusion (J/kg or kJ/kg): solid ↔ liquid

Latent heat of vapourisation (J/kg or kJ/kg): liquid ↔ gas