Physics 9 Flashcards
Particle model, atomic structure (37 cards)
Draw and label an atom.
Include the three components that an atom is made of.
What is the charge of each of these particles?
Protons - positive
Neutrons - neutral
Electrons - negative
Define nuclear radiation.
The energy carried by particles from a radioactive substance or spreading out from a source.
Name some sources of background radiation.
Cosmic/sun’s rays
Nuclear disasters/accidents
Natural sources such as rocks (e.g. granite)
Describe the structure of α radiation. Include its symbol.
2 protons, 2 neutrons (the same as a helium nucleus)
4
α
2
Describe the structure of β radiation. Include its symbol.
A single electron
0
β
-1
Describe the structure of γ radiation. Include its symbol.
An electromagnetic wave (photon)
0
γ
0
Define half-life.
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.
Explain how Rutherford and Marsden discovered the structure of the atom.
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.
What is an isotope?
Atoms of an element with the same number of protons and electrons but different numbers of neutrons.
What are the three types of nuclear radiation? Order them from least penetrating to most penetrating.
α alpha
β beta
γ gamma
What is meant by the term “ionising radiation”?
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.
What do the numbers represent?
4
He
Helium
2
4: Atomic mass (nucleus, number of protons + number of neutrons)
2: Atomic number (number of protons)
How can we find out the number of electrons in an atom?
By looking at the number of protons.
number of protons = number of electrons
What is the symbol for a neutron? What is a neutron made of?
1
n
0
Do some decay equations.
Sketch the shape of a half-life graph.
Explain contamination.
When unwanted radioactive isotopes end up on other materials, skin or clothing.
How could we reduce levels of contamination?
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)
Explain how a medical tracer works
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.
Explain how x-rays work.
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.
Explain radiotherapy.
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.
Explain brachytherapy.
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
If nuclear radiation can cause harm to the body, justify why we still use it in medicine?
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.
Complete a table on solids, liquids and gases.
Label the processes in a “changes of state” triangle.
What is the density triangle? What are the units
/ M \
/ ρ | V \
______
density* = kg/m³ or g/m³ mass = kg or g volume = m³ or cm³*
