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Question	Answer
Alpha radiation is strongly	ionising radiation. Beta radiation is
Alpha(α) is radiation that is [] []	strongly ionising, travels a few centimeters in	air and is stopped by a thin sheet of	paper.
Beta(β) is [] radiation	ionising radiation that penetrates [] or several sheets of []	card or several sheets of paper, but is stopped by a sheet of aluminium or other metal that's	3mm thick.
Gamma(γ) is [][] radiation	weakly ionising radiation, it is reduced significantly by a thick sheet of	lead or blocks of	concrete.
The most penetrating type of radioactive emission is	gamma radiation.
Alpha and beta radiation is deflected by both	magnetic fields and electric fields, but gamma radiation is not	affected.
Background radiation: radioactive materials occur n...	natuarally, and can also be made a...	artificially.
We recieve a low level of radiation called	background radiation.
Building materials, rocks(e.g. granite) and soil; radioactive nuclei in all plants and animals; medical and industrial uses of radioactive materials and 'leaks' from radioactive waste and nuclear power station are whence comes	background radiation.
Background radiation is radioactive emissions from	nuclei in our	surroundings.
In some parts of a country, the rocks may be more radioactive than the rocks in other parts and there is a higher level of	background radiation.
Ionising radiation is radiation that has enough energy to break [] or []	molecules or atoms into [] called []	charged particles called ions.
"The molecules or atoms lose electrons in a process called	ionisation. The ions can take part in	chemical reactions. The is how ionising radiation damages	living cells.
To damage living cells, ionising radiation either [] them	kills them or damages the [] in the cell	the DNA in the cell, so that the cell [] into a [] cel	mutates into a cancer cell.
Ionising radiation includes alpha, beta and gamma radiation from the [] []	radioactive nuclei and also []-[] and []-[] radiation	also x-rays and ultra-violet radiation.
Of all the radioactive emission, the most ionising are	alpha particles, followed by	beta, and the least ionising being	gamma.
Gamma rays, X-rays and ultra-violet radiation are three types of [] radiation	electromagnetic radiation with high enough frequency to cause	ionisation.
"It is not possible" to predict which cells will be damaged by exposure to	radiation, and "it is not possible" to say who will get c...	cancer. Scientists have studied the survivors of incidents where people have been expose to ionising radiation. They measured the amount of exposure and recorded how many people later suffered from cancer. They introduce radiation dose, measured in	sieverts, which is a measure of the	possible harm done to the body. Radiation dose depends on the type of	radiation, the time of	exposure and how sensitive the tissue exposed to	radiation. Scientists can then give a figure for the risk of cancer	developing.
To reduce the risk to living cells, radioactive materials must be handled	safely: wear protective	clothing, make your distance away	long, handle sources with	tongs, keep the exposure time	short, sources should be s...	shielded and labelled with the	radioactive symbol. "These precautions keep the dose as low as possible".
Radioactive materials are used, for example, in hospitals and nuclear power stations. "Employers must keep the dose for their employees As Low As Reasonably Achievable: this is known as the	alara principle. Employees at places where nuclear sources are used, may wear a film badge to monitor the exposure to radiation. Hospital staff may move behind a screen or out of the room during X-ray photo graphs.
Uses of radioactivity.
For each use: the radiation is chosen depending on the r[] and the a[]	on the range and the absorption, the source is chosen depending on how long it will remain	radioactive. [Medical and health uses]. [Medical tracers]. Sources which emit gamma radiation (or sometimes beta radiation) are used in medical t...	medical tracers. The patient drinks, inhales, or is injected with the	tracer which is chosen to target the organ the doctor(s) want to examine. For example, radiactive iodine is taken up by the [] gland	tyroid gland, which can then be viewed using a	gamma camera that detects	gamma radiation passing through the	body.
A tracer must no decay before it has moved to the organ being	investigated, but must not last so long that the patient, for weeks afterwards, stays	radioactive. Sources which emit a higher dose of gamma radiation are used in the same way for treating	cancer by, in the cell,	building up and killing the	cancer cells.
Treating cancer. Directed at a cancer is a b...	beam of	gamma rays to kill the	cancer cells. One source of this is [c...]-[]	cobalt-60. It emits [] rays	gamma rays of high	energy and remains radioactive for	years.
Sterillisation. Sources which emit gamma radiation are used to produce a beam of	gamma rays that will: [] equipment, such as surgical instruments,	sterilise equipment by destroying	microbes; extend the shelf-life of	"perishable food", by	destroying microbes. The food and equipment does not become radioactive, because it is only irradiated. It does not touch the [r...] [m...]	radioactive material, so there is no contamination.
Other uses of radioactivity. Smoke detectors. Smoke detectors use sources that are	radioactive and emit	alpha radiation. The radiation from the sources [] the air	ionise the air and ions cross a small	gap and are picked up by a	detector. If smoke is present, the alpha radiation is stopped by	smoke particles. No ions reach the	detector and and alarm is sounded. Beta and gamma radiation are unsuitable as they	pass through the smoke.
Tracers. Souuces which emit beta radiation or gamma radiation are used as	tracers. A detector can be used to track where it goes, because a tracer is	radioactive. If a tracer is added to sewage at an ocean outlet, or as it enterrs a rive, then the movement can be	traced. Leaks in power station heat exchangers can be	tracked. The source used is carefully selected to be one with a radioactivity that can quickly fall to	0, after the	test(is done).
Paper thickness detectors. Used in radioactive paper thickness detectors are radioactive sources that emit	beta radiation. The sheet of paper is between rollers, there is a machine to adjust the rollers, there is a source of radiation above the paper, and the is a detector below the paper. Some of the beta radiation is, by the paper sheet,	absorbed. If the sheet is too thick, less beta radiation is	detected and the pressure of the rollers is	increased. If the sheet is too thin: more beta radiation is	detected and the pressure is	reduced.
Non destructive testing. Another use of gamma radiation sources is non-destructive testing. An aircraft wing can be examined for minute cracks by placing, on one side, a strong [] source	gamma source and on the other side a	detector-in a similar way to using X-rays to check for broken bones.
Changes in the Nucleus
The nucleus and the isotopes. The atom is mostly empltyn space with almost all the mass concentrated in teh small positively charged	nucleus at the	centre. The nucleus of an atom contains two types of particle: neutrons, which have no	charge; and protons, which each have a [s...] [p...] [c...]	single positive charge. The nucleus is surrounded e orbiting	electrons which have very little	mass. Each electron has a charge that's	negative. A neutral atom has an equal number of	protons and electrons.
Different elements. "The number of protons in the nucleus decides which element the atom is, so for example, hydrogen always has one	proton, helium has	two, lithium has	three and so on. Carbon always has	six."
Isotopes. The number of neutrons in the nucleus can	vary. An isotope is a [] of a []	nucleus of an element with the same number of	protons but different number of	neutrons. Some isotopes are stable, but others are	unstable. Unstable isotopes are	radioactive because they emit	nuclear radiation in a process called	radioactive decay.
Isotopes of the same element have exactly the same [] properties	chemical properties, but they have different [d...] and nuclear []	density and nuclear stability. Different isotopes are referred to by the	number of nucleons in the nucleus, fo rexample, carbon-12 has [] protons and [] neutrons	6 protons and 6 neutrons, whereas carbon-14 has [] protons and [] neutrons	6 protons and 8 neutrons.
Radioactive decay. A radioactive nucleus is un...	unstable and emits	nuclear radiation. This process is called	radioactive decay. "It is not possible to predict when this will happen, nor is it possible to make it happen by a chemical or physical process, (for example by heating it.) The decay is random."
Radioactive emissions. Alpha emissions is when t	two protons and two neutrons leave the nucleus as one particle. The alpha particle is identical to a [] nucleus	helium nucleus. For example, the isotope of radon gas, radon-	220, decays by	alpha emission. Beta emission occurs when a neutron decays to a [] and []	proton and an electron and the electron	leaves the nucleus. The beta particle is a high energy	electron.
The radioactive isotope of carbon, carbon-14 decays by	beta emission. carbon-14 [arrow]	nitrogen 14 + beta particle. A beta particle is an [] from the [] - not an orbital electron	electron from the nucleus. An Alpha particle is two [] and two []	two - a [] nucleus	a helium nucleus. A beta particle is a high energy particle from the	nucleus. Gamma radiation is a high-[] and short []	high-frequency and short wavelength [] wave	electromagnetic wave.
HALF-LIFE. A radioactive source contains millions of n...	nuclei. The number of nuclei decaying per unit time is called the [] of the source.	activity of the source. "The activity depends on two things:" the type of	isotope - some isotopes are more [] that others	more stable than others; the number of undecayed	nuclei in the	sample - double he number of nuclei and, on average, there will be double the number of [] per []	decays per second. The half-life of an isotope is the average time taken for	half of the active nuclei to decay.
Technetiun-99m (T -99m) decays by	gamma emission to technetium-99 (Tc-99) with a half-life of	six hours. After six hours, on average, only half of the Tc-99m nuclei remain	active. After another six hours, on AVERAGE, the amount of nuclei active is	one quarter. This pattern is the same for all isotopes but the value of the half-life is	different.Carbon-14 has a half-life of	5730 years, but some isotopes have a half-life of less than a s...	econd.
Tc99m is one of the most widely used radioactive isotopes in	medicine. It is used to diagnose problems in many	organs. The half-life of six hours means that the radiation last only long enough for the isotope to travel to the [] being investigated	organ being investigated. Its activity decreases rapidly and "cannot" be [] after a few []	detected after a few days. Tc-99m does not occur n...	"naturally" - it is made in	"reactors".
DATING. The amount of carbon-14 in a living objct is fixed when it	dies. The carbon-14 d...	decays, so that a wooden spear that is 5730 years old has only half the carbon-14 left that it had when it was	made. Objects that once lived can be [] dated	carbon dated by the amount of [] that is left	carbon-14 that is left.
Some rocks contain a radioactive isotope of	uranium that decays to	lead, so they can be dated by the [] - [] []	uranium - lead ratio, the more lead there is, the [] the rock is.	the older the rock is. Because of small amounts of isotopes involved, and the long half-lifes, these methods "cannot" be used to find dates to find dates to within []s of years	tens of years. They are "not" useful for objects that are less then a [] years old.	hundred years old.
NUCLEAR REACTORS
NUCLEAR FISSION. If a nucleus of uranium-235 absorb a neutron, it becomes very	unstable and can be split into two	nuclei of about equal	size, and two or three	neutrons. This process is called	nuclear fission. When this happens, there is a release of a lot of	nuclear energy, about a million times more than the energy released in a	chemical reaction.
The neutrons released in nuclear fission can strike more	uranium nuclei and cause more [] reactions	fission reactions - which in turn produce more	neutrons, and so on. This is called a	chain reaction. If the fission reaction runs out of control it is an	atomic bomb, but if the process is controlled, the energy released can be used to generate	electricity. This is how a [] in a power station works.	nuclear reactor in a power station works.
The fuel rods contain	uranium-235 and are put in the	reactor. The reaction can be [] or []	controlled or stopped by using a material that [] []	absorbs neutrons. The neutron absorbing material is made into	control rods. The control rods are moved into the	reactor to absorb neutrons, and [] or [] the reactions.	slow or stop the reactions, and out of the reactor to increase the	reaction.
The energy heats up the [] [] and [] []	fuel rods and control rods. A coolant is	circulated to	remove the heat from the reactor. When the coolant has been	heated, it is used to	heat water to steam for the power station. When the coolant is cool, it, again,	circulated through the reactor.
Another isotope, instead of uranium-239, nucleus, is plutonium-	239.
WASTE DISPOSAL. Radioactive waste is dangerous to living things and must be carefully	disposed of. "The half-life of some isotopes is thousands, or millions, of years, so radioactive material must be disposed of in a way that will keep it safely contained for thousands of years". There are three types of radioactive waste:	low-level waste(for example, used protective clothing), intermediate-level waste(for example, material and reactors) and high-level waste(for example, used fuel rods). Low level waste can be, into containers,	sealed and put in [] sites	landfill sites. Intermediate-level waste is mixed with	concrete and stored in	stainless-steel containers. "It must be stored for thousands of years".
High-level was is kept, at first, in	cooling tanks, because it [] so fast	decays so fast it gets	hot. Eventually it becomes	intermediate-level waste. High-level waste includes '[] grade plutonium'	'weapon grade plutonium', which is the radioactive element plutonium, "produced in nuclear reactors". It can be used to make [] weapons	nuclear weapons.
Waste can be dispersed (for example when sewage is discharged in the	sea), or contained (for example when rubbish is put in a [] site	landfill site). Some radioactive waste is too dangerous to be	dispersed.
Where to store the waste? At the bottom of the	sea - but containers may	leak; under-[]	underground - but containers may	lead, and [] or other changes to the rocks may occur.	earthquakes or other changes to the rocks; on the	surface - but "needs	guarding" (for example, from terrorists) for thousands of years."
\|ENERGY\|
THE EFFECT OF HEATING
Temperature and heat. Temperature is a measure of how [] an object is	how hot an object is. The temperature scale we use measures temperature in	degrees Celsius. On this scale 0 degrees is defined as the temperature at which [] [] []	pure ice melts - but temperatures can be much lower than this. Different temperatures can be shown on a [] - each colour represents a different temperature	thermogram - each colour represents a different temperature. Heat is a form of	energy. If an object is cooled until all the particles stop moving then they cannot lose any more [] energy	kinetic energy. The amount of heat in the object is a	minimum.
Specifice hear capacity. If the temperature of a solid, liquid or gas changes, then it has gained, or lost,	energy. The amount of energy depends on: the temperature	change, the object's	mass, the object's	material.
The specific heat capacity of a material is a measure of the material's	energy. For different materials, it is	different and tells us how much	energy (in	joules) you need to [] the []	raise the temperature of one	kilogram of the material by	one degree Celsius.
The specific heat capacity ('specific' means 'for each kilogram') heat capacity of a material is the [] needed	energy needed to increase the temperature of 1kg of the material by 1 degree celsius: Energy = [] x [] x []	mass x specific heat capacity x temperature change. Specific heat capacity is measured in	J / kg °C.
Latent heat. Heating an object raises its	temperature except at the [] [] and [] []	melting point and boiling point. At these temperatures, the energy is being used to change the	state, from solid to liquid, or liquid to gas. Because the temperature does not change, the heat given to the substance is called	latent heat('latent' means hidden).
Solid objects are held together by forces between the	particles([] or [])	heated, [] more	(atoms or molecules), and have a regular shape. The particles, as the object is	vibrate more. Liquid particles have enough	energy to break the inter-[] []	inter-molecular bonds and [] over each other.	slide over each other.
At the melting point, heating the solid does not increase the	vibrations, but gives the particles enough	energy to [] the []	break the bonds. When a liquid freezes, it loses this	energy to its	surroundings.
Here is the equation relating energy to specific heat capacity: E = m × c × θ	m × c × θ. E is the [] [] in [], []	E is the energy transferred in joules, J; m is the[...] in []	m is the mass of the substance in kg; c is the [] in []	c is the specific heat capacity in J / kg °C; θ (‘theta’) is the [...] in [...], []	θ (‘theta’) is the temperature change in degrees Celsius, °C.
Gas particles have enough energy to completely	seperate. Heating the liquid completely breaks the []-[] []	inter-molecular bonds and the particles form a	gas.
When an object changes from solid to liquid, there is a small increase in [] energy	kinetic energy; when a liquid changes to gas, there is an [] that's []	increase that's bigger.
The specific latent heat of melting of a material is the [] in []	energy in joules "needed" to	melt 1kg of the material without changing its temperature.
ALLEDGEDLY POSSIBLY
A radioactive nucleus is un	stable and will emit	radiation. The three main types or radioactive emissions are (with symbols)	Alpha(α), Beta(β) and Gamma(γ).
Contamination or irradiation? If a person has a radioactive material on their skin or clothes, or has swallowed or inhaled it, this is called	radioactive contamination. Over a period of time, the radioactive material will	decay. This results in a higher dose of radiation than being exposed to a source that's	external, because when a person moves away from the source they are no longer	irradiated. This is especially true of the type of radiation that's	alpha radiation. Unlike beta and gamma radiation, alpha radiation cannot penetrate the	skin, so outside the body - a few centimetres away - it is not	dangerous. But if a person inhales, or swallows, material that emits alpha particles, inside the body, the source will continue to emit until all the radioactive nuclei have	decayed. This increases the risk of cancer.

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