P4 Spaced learning Radiation for life

Sparks Positive and negative charges Insulating materials Metals are good conductors, which means that electric charges move easily through them. Materials such as plastic, wood, glass and polythene are insulators. This means they do not allow electric charges to move through them. Some insulators can become electrically charged when they're rubbed together. Positive and negative charges Objects can be positively charged, negatively charged or neutral (no charge). A substance that gains electrons becomes negatively charged, while a substance that loses electrons becomes positively charged. Atoms or molecules that become charged are ions. When a charged object comes near to another object they will either attract or repel each other If the charges are the same - they repel If the charges are opposite - they attract If one is charged and the other is not - they attract. Like charges repel, and unlike charges attract. Problems with static electricity Static is a nuisance when: Dust and dirt is attracted to insulators such as TV screens and computer monitors Clothes made from synthetic materials often cling to each other and to the body, especially just after they've been in a tumble drier. Static is dangerous when: There are flammable gases or vapours or a high concentration of oxygen. A spark could ignite the gases and cause an explosion You touch something with a large electric charge on it. The charge will flow through your body causing an electric shock. This could cause burns or even stop your heart. Safety measures - Higher tier The chance of receiving an electric shock can also be reduced if: An object that might become charged is earthed by an earth wire In a factory, machinery operators stand on insulating mats or wear shoes with insulating soles. Lorries containing flammable gases, liquids and powders are earthed by an earth wire before being unloaded.

Uses of electrostatics Electrostatic precipitators The electrostatic precipitator is a device used in chimneys for removing dust. Spraying Electrostatics can be useful for spraying liquids. For example: spraying paint spraying crops with pesticides and herbicides. Spraying paint They work because like charges repel and unlike charges attract. The spray gun is given a charge. So droplets of point become charged: They have the same charge, so repel each other producing a fine spray. The car body part is has the opposite charge. The paint droplets are attracted to the body part, producing an even coat with little waste. Defibrillators A defibrillator is a machine that can be used by paramedics to stabilise an irregular heartbeat. They work by discharging electric charge. Two paddles with insulated handles are charged from a high voltage supply. They are put in good electrical contact with the patient's chest. It is important that only the patient gets a shock: This is why the paddles have insulating handles The operator and any one nearby stand clear. The defibrillator passes charge through the patient to make the heart contract Higher Tier The metal grids in the electrostatic precipitator are given a high voltage. Depending on the design, the grids may be positively charged or negatively charged dust particles lose electrons if the grids are positively charged dust particles gain electrons if the grids are negatively charged. The charged dust particles then induce a charge on the earthed metal collecting plates and the dust particles are attracted to the plates. Higher Tier The paint gun loses electrons so that it becomes positively charged The paint droplets lose electrons and so also become positively charged The object to be painted gains electrons and so becomes negatively charged The positively charged paint droplets repel each other and are attracted to the negatively charged surface.

Safe electricals Current Resistance Cables and plugs Fuses Electric current is a flow of electric charge. No current can flow if the circuit is broken, for example, when a switch is open Resistance There is a resistance to the flow of an electric current through most conductors. Resistance is measured in ohms, Ω. The resistance in a wire increases (and the current decreases) as: The length of the wire increases The thickness of the wire decreases Cables and plugs Colour Wire Function Blue Neutral Completes the circuit Brown Live Carries the high voltage Green and yellow stripes Earth A safety wire to stop the appliance becoming live To check for a complete circuit, follow a wire coming out of the battery with your finger. You should be able to go out of the battery, through the lamp and back to the battery. Resistors are added into a circuit to reduce the amount of current flowing. The greater the resistance, the lower the current. A variable resistor or rheostat is a device whose resistance can be changed. It can be used to vary the amount of current in a circuit. Fuses The fuse breaks the circuit if a fault in an appliance causes too much current flow. Resistance = voltage ÷ current Resistance is measured in ohms, Ω Voltage (potential difference) is measured in volts, V Current is measured in amperes (amps), A Double insulation Some appliances do not have an earth wire as they have plastic casings Calculating power: Higher Tier You can work out power using this equation: Power = voltage × current Power is measured in watts, W Voltage (potential difference) is measured in volts, V Current is measured in amperes (amps), A

Ultrasound Waves Longitudinal waves Ultrasound All sound is produced by vibrating particles that form longitudinal waves. In this kind of wave the vibrations of the particles are in the same direction as the wave Ultrasound Ultrasound is the name given to sound waves that have frequencies greater than 20,000Hz. It's too high pitched for human hearing, but many animals, such as dogs, cats and bats can hear ultrasound. Ultrasound has many applications in medicine. These include: Looking inside people by scanning the body Breaking down kidney stones and stones elsewhere in the body Measuring the speed of blood flow in the body Terms you need to know are: Amplitude - The maximum distance the particles move from their normal position. The louder a sound is, the more energy it carries and the bigger its amplitude. Wavelength - The distance between one high pressure region (compression) and the next. Frequency - The number of waves produced in one second, measured in hertz, Hz. A higher pitched sound has a higher frequency than a lower pitched sound. Compression - A region of higher pressure where particles are squashed together. Rarefaction - A region of lower pressure where particles are spread out. Ultrasound - Higher tier Ultrasound may be used instead of x-rays for certain scans, such as scan of unborn babies. Compared to x-ray photographs, ultrasound scans: Do not damage living cells Produce images of soft tissue Medical images from ultrasound Ultrasound is sent into the patient's body. Some of the ultrasound is reflected at each boundary between different tissues or organs. Breaking down kidney stones A high powered ultrasound wave is used to break down kidney stones and other stones in the body. The stones vibrate until they shake themselves apart and are then easily passed out of the body via the urethra

What is radioisotopes Half-life Ionisation Higher tier - Ionsation There are three main types of radiation, called alpha, beta and gamma radiation, which all have different properties. Type of radiation What is it? Alpha particle Two protons and two neutrons – the same as a helium nucleus Beta particle Fast-moving electron Half-life This is how long it takes for half the nuclei of a piece of radioactive material to decay. This is called the half-life of the radioactive isotope. There are two definitions of half-life, but they mean essentially the same thing. Half-life is the time taken for: The number of nuclei of the radioactive isotope in a sample to halve The count rate from a sample containing the radioactive isotope to fall to half its starting level Ionisation Nuclear radiation ionises materials. Ionisation happens when: Particles lose electrons and become positively charged Particles gain electrons and become negatively charged Higher tier - Ionsation Ionisation can be harmful to living cells. Alpha particles are particularly good ionisers. They have a much larger mass, and a greater charge, than beta particles. Higher Tier - Decay Alpha decay Two protons and two neutrons are lost from a nucleus when it emits an alpha particle: The atomic mass number decreases by 4 and the atomic number decreases by 2 A new element is formed that is two places lower in the periodic table than the original element. Beta decay In beta decay a neutron changes into a proton plus an electron. The proton stays in the nucleus, the electron leaves the atom with high energy as a beta particle. The nucleus has one more proton and one less neutron when it emits a beta particle: The atomic mass number stays the same but the atomic number increases by one A new element is formed that is one place higher in the periodic table than the original element.

Use of radioisotope Background radiation Tracers Smoke detectors Background radiation is all around us. Some of it comes from natural sources and some comes from artificial sources. Natural sources Cosmic rays – radiation from space Rocks and soil – some rocks are radioactive and give off radioactive radon gas Living things – plants absorb radioactive materials from the soil and these pass up the food chain Tracers Radioisotopes are used as tracers in industry. These are used for tracking substances.: Find leaks or blockages in underground pipes Find the route of underground pipes Track the dispersal of waste Smoke detectors Smoke detectors alert people to fires. Smoke from the fire is detected by the device, which then gives off an alarm. One type of smoke detector uses americium-241, a source of alpha radiation, to detect smoke Dating rocks Radioactivity can be used to date rocks. Rocks often contain traces of uranium. This is unstable and eventually decays to lead, which is stable. The age of a rock can be calculated if its ratio of uranium to lead is known. The older the rock, the lower its uranium to lead ratio: Young rocks have a high uranium to lead ratio Very old rocks have a low uranium to lead ratio Artificial sources human activity has added to background radiation by creating and using artificial sources of radiation. These include radioactive waste from nuclear power stations, radioactive fallout from nuclear weapons testing medical x-rays. Higher tier Carbon-14 is a radioactive isotope. It is found in the air in carbon dioxide molecules. The amount of carbon-14 in the air has stayed the same for thousands of years. There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain. Once an organism dies, it stops taking in carbon-14. The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.

Treatment Uses of radiation in medicine Sterilising equipment Tracers X-rays, gamma rays and beta particles are all used in medicine to treat internal organs. X-rays are produced by firing electrons at a metal target and gamma rays are emitted by the nucleus of radioactive atoms. Gamma rays are used to kill cancer cells, to sterilise medical equipment and in radioactive tracers. Uses of radiation in medicine Sterilising equipment Gamma rays are high energy electromagnetic waves which are only stopped by thick lead. This means they can easily pass through medical equipment, such as syringes. Tracers Radioactive tracers are used to investigate a patient's body without the need for surgery. Gamma emitters beta emitters are used because gamma rays and beta particles can pass through skin, whereas alpha particles cannot. 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. Tracers and treating cancer - Higher tier Tracers Radioisotopes with short half-lives are chosen to make sure that the tracer does not stay radioactive in the body for long periods. The radioactive tracer is put into the body by one of the following ways: By an injection By ingestion Treating Cancer Gamma rays damage cells whether they are normal or cancerous, so gamma rays must be focused on the tumour. One way of doing this is to use a wide beam of gamma rays, but to rotate the beam around the patient, keeping the tumour at the centre. This concentrates the gamma rays on the cells that need to be killed.

Fission and Fusion Chain Reaction Higher Tier - Nuclear Fission Nuclear fission is the splitting of atomic nuclei. Nuclear power stations use the fission of uranium-235 to heat water. Fusion is the joining of atomic nuclei. Chain Reaction The fission of uranium can set up a chain reaction that will keep on releasing energy as long as there are uranium nuclei present. If this chain reaction is allowed to get out of control, energy is released very quickly and the result is a nuclear bomb. Nuclear power stations are designed to keep chain reactions under control Higher Tier - Nuclear Fission For fission to happen, the uranium nucleus must be hit by a neutron. When this happens: The nucleus splits into smaller nuclei, Energy is released and Two or three neutrons are released. Fuel produces heat, which is used to boil water to make steam. Steam spins a turbine. Turbine drives a generator and the generator makes electricity. Electricity goes to the transformers to produce the correct voltage. Uranium is a non-renewable energy resource and, like the fossil fuels, it cannot be replaced once it has all been used up. Nuclear fusion Nuclear fission is the splitting of large nuclei into smaller ones, while nuclear fusion is the joining of smaller nuclei to make larger ones. Nuclear fusion happens in stars and fusion bombs Higher Tier – Nuclear Fusion The Sun and other stars use nuclear fusion to release energy. The sequence of nuclear fusion reactions in a star is complex but overall hydrogen nuclei join to form helium nuclei. Cold fusion A group of scientists have claimed that they have achieved ‘cold fusion’ – nuclear fusion at ordinary temperatures and pressures. If it happens, cold fusion could be developed to provide almost limitless and cheap electricity. It would also make the international project to develop a fusion power station using high temperatures and pressures pointless.

Sparks Positive and negative charges Insulating materials Metals are good conductors, which means that electric charges move easily through them. Materials such as plastic, wood, glass and polythene are insulators. This means they do not allow electric charges to move through them. Some insulators can become electrically charged when they're rubbed together. Positive and negative charges Objects can be positively charged, negatively charged or neutral (no charge). A substance that gains electrons becomes charged, while a substance that loses electrons becomes charged. Atoms or molecules that become charged are . When a charged object comes near to another object they will either attract or repel each other If the charges are the same – If the charges are opposite – If one is charged and the other is not – Like charges. Problems with static electricity Static is a nuisance when: Static is dangerous when: Safety measures - Higher tier The chance of receiving an electric shock can also be reduced if:

Sparks Positive and negative charges Insulating materials Metals are good conductors, which means that electric charges move easily through them. Materials such as plastic, wood, glass and polythene are insulators. This means they do not allow electric charges to move through them. Some insulators can become electrically charged when they're rubbed together. Positive and negative charges Objects can be positively charged, negatively charged or neutral (no charge). A substance that gains electrons becomes negatively charged, while a substance that loses electrons becomes positively charged. Atoms or molecules that become charged are ions. When a charged object comes near to another object they will either attract or repel each other If the charges are the same - they repel If the charges are opposite - they attract If one is charged and the other is not - they attract. Like charges repel, and unlike charges attract. Problems with static electricity Static is a nuisance when: Dust and dirt is attracted to insulators such as TV screens and computer monitors Clothes made from synthetic materials often cling to each other and to the body, especially just after they've been in a tumble drier. Static is dangerous when: There are flammable gases or vapours or a high concentration of oxygen. A spark could ignite the gases and cause an explosion You touch something with a large electric charge on it. The charge will flow through your body causing an electric shock. This could cause burns or even stop your heart. Safety measures - Higher tier The chance of receiving an electric shock can also be reduced if: An object that might become charged is earthed by an earth wire In a factory, machinery operators stand on insulating mats or wear shoes with insulating soles. Lorries containing flammable gases, liquids and powders are earthed by an earth wire before being unloaded.

Uses of electrostatics Electrostatic precipitators The electrostatic precipitator is a device used in chimneys for removing dust. Spraying Electrostatics can be useful for spraying liquids. For example: spraying paint spraying crops with pesticides and herbicides. Spraying paint They work because like charges repel and unlike charges attract. The spray gun is given a charge. So droplets of point become charged: They have the same charge, so repel each other producing a fine spray. The car body part is has the opposite charge. The paint droplets are attracted to the body part, producing an even coat with little waste. Defibrillators A defibrillator is a machine that can be used by paramedics to stabilise an irregular heartbeat. They work by discharging electric charge. Two paddles with insulated handles are charged from a high voltage supply. They are put in good electrical contact with the patient's chest. It is important that only the patient gets a shock: This is why the paddles have insulating handles The operator and any one nearby stand clear. The defibrillator passes charge through the patient to make the heart contract Higher Tier The metal grids in the electrostatic precipitator are given a high voltage. Depending on the design, the grids may be positively charged or negatively charged dust particles lose electrons if the grids are positively charged dust particles gain electrons if the grids are negatively charged. The charged dust particles then induce a charge on the earthed metal collecting plates and the dust particles are attracted to the plates. Higher Tier The paint gun loses electrons so that it becomes positively charged The paint droplets lose electrons and so also become positively charged The object to be painted gains electrons and so becomes negatively charged The positively charged paint droplets repel each other and are attracted to the negatively charged surface.

Uses of electrostatics Electrostatic precipitators The electrostatic precipitator is Spraying Electrostatics can be useful for spraying liquids. For example: Spraying paint They work because like charges repel and unlike charges attract. Defibrillators A defibrillator is a machine that can be used by paramedics to stabilise an irregular heartbeat. They work by discharging electric charge. Higher Tier Higher Tier

Safe electricals Current Resistance Cables and plugs Fuses Electric current is Resistance There is a resistance to the flow of an electric current through most conductors. Resistance is measured in ohms, Ω. Cables and plugs Colour Wire Function Blue Neutral Completes the circuit Brown Live Carries the high voltage Green and yellow stripes Earth A safety wire to stop the appliance becoming live To check for a complete circuit, follow. Resistors are added into a circuit to . Fuses . Resistance = voltage ÷ current Resistance is measured in Voltage (potential difference) is measured in Current is measured in Double insulation Calculating power: Higher Tier You can work out power using this equation: Power = X Power is measured in watts, W Voltage (potential difference) is measured in volts, V Current is measured in amperes (amps), A

Safe electricals Current Resistance Cables and plugs Fuses Electric current is a flow of electric charge. No current can flow if the circuit is broken, for example, when a switch is open Resistance There is a resistance to the flow of an electric current through most conductors. Resistance is measured in ohms, Ω. The resistance in a wire increases (and the current decreases) as: The length of the wire increases The thickness of the wire decreases Cables and plugs Colour Wire Function Blue Neutral Completes the circuit Brown Live Carries the high voltage Green and yellow stripes Earth A safety wire to stop the appliance becoming live To check for a complete circuit, follow a wire coming out of the battery with your finger. You should be able to go out of the battery, through the lamp and back to the battery. Resistors are added into a circuit to reduce the amount of current flowing. The greater the resistance, the lower the current. A variable resistor or rheostat is a device whose resistance can be changed. It can be used to vary the amount of current in a circuit. Fuses The fuse breaks the circuit if a fault in an appliance causes too much current flow. Resistance = voltage ÷ current Resistance is measured in ohms, Ω Voltage (potential difference) is measured in volts, V Current is measured in amperes (amps), A Double insulation Some appliances do not have an earth wire as they have plastic casings Calculating power: Higher Tier You can work out power using this equation: Power = voltage × current Power is measured in watts, W Voltage (potential difference) is measured in volts, V Current is measured in amperes (amps), A

Ultrasound Waves Longitudinal waves Ultrasound All sound is produced by vibrating particles that form longitudinal waves. In this kind of wave the vibrations of the particles are in the same direction as the wave Ultrasound Ultrasound is the name given to sound waves that have frequencies greater than 20,000Hz. It's too high pitched for human hearing, but many animals, such as dogs, cats and bats can hear ultrasound. Ultrasound has many applications in medicine. These include: Terms you need to know are: Amplitude – Wavelength – Frequency – Compression – Rarefaction - Ultrasound - Higher tier Medical images from ultrasound Breaking down kidney stones

Ultrasound Waves Longitudinal waves Ultrasound All sound is produced by vibrating particles that form longitudinal waves. In this kind of wave the vibrations of the particles are in the same direction as the wave Ultrasound Ultrasound is the name given to sound waves that have frequencies greater than 20,000Hz. It's too high pitched for human hearing, but many animals, such as dogs, cats and bats can hear ultrasound. Ultrasound has many applications in medicine. These include: Looking inside people by scanning the body Breaking down kidney stones and stones elsewhere in the body Measuring the speed of blood flow in the body Terms you need to know are: Amplitude - The maximum distance the particles move from their normal position. The louder a sound is, the more energy it carries and the bigger its amplitude. Wavelength - The distance between one high pressure region (compression) and the next. Frequency - The number of waves produced in one second, measured in hertz, Hz. A higher pitched sound has a higher frequency than a lower pitched sound. Compression - A region of higher pressure where particles are squashed together. Rarefaction - A region of lower pressure where particles are spread out. Ultrasound - Higher tier Ultrasound may be used instead of x-rays for certain scans, such as scan of unborn babies. Compared to x-ray photographs, ultrasound scans: Do not damage living cells Produce images of soft tissue Medical images from ultrasound Ultrasound is sent into the patient's body. Some of the ultrasound is reflected at each boundary between different tissues or organs. Breaking down kidney stones A high powered ultrasound wave is used to break down kidney stones and other stones in the body. The stones vibrate until they shake themselves apart and are then easily passed out of the body via the urethra

What is radioisotopes Ionisation Higher tier – Ionsation There are three main types of radiation, called alpha, beta and gamma radiation, which all have different properties. Type of radiation What is it? Alpha particle Two protons and two neutrons – the same as a helium nucleus Beta particle Fast-moving electron There are two definitions of half-life, but they mean essentially the same thing. Half-life is the time taken for: Ionisation Nuclear radiation ionises materials. Ionisation happens when: Higher tier – Ionsation Higher Tier - Decay Alpha decay Beta decay

What is radioisotopes Half-life Ionisation Higher tier - Ionsation There are three main types of radiation, called alpha, beta and gamma radiation, which all have different properties. Type of radiation What is it? Alpha particle Two protons and two neutrons – the same as a helium nucleus Beta particle Fast-moving electron Half-life This is how long it takes for half the nuclei of a piece of radioactive material to decay. This is called the half-life of the radioactive isotope. There are two definitions of half-life, but they mean essentially the same thing. Half-life is the time taken for: The number of nuclei of the radioactive isotope in a sample to halve The count rate from a sample containing the radioactive isotope to fall to half its starting level Ionisation Nuclear radiation ionises materials. Ionisation happens when: Particles lose electrons and become positively charged Particles gain electrons and become negatively charged Higher tier - Ionsation Ionisation can be harmful to living cells. Alpha particles are particularly good ionisers. They have a much larger mass, and a greater charge, than beta particles. Higher Tier - Decay Alpha decay Two protons and two neutrons are lost from a nucleus when it emits an alpha particle: The atomic mass number decreases by 4 and the atomic number decreases by 2 A new element is formed that is two places lower in the periodic table than the original element. Beta decay In beta decay a neutron changes into a proton plus an electron. The proton stays in the nucleus, the electron leaves the atom with high energy as a beta particle. The nucleus has one more proton and one less neutron when it emits a beta particle: The atomic mass number stays the same but the atomic number increases by one A new element is formed that is one place higher in the periodic table than the original element.

Use of radioisotope Background radiation Tracers Smoke detectors Background radiation is all around us. Some of it comes from natural sources and some comes from artificial sources. Natural sources Tracers Smoke detectors Dating rocks Artificial sources human activity has added to background radiation by creating and using artificial sources of radiation. These include Higher tier

Use of radioisotope Background radiation Tracers Smoke detectors Background radiation is all around us. Some of it comes from natural sources and some comes from artificial sources. Natural sources Cosmic rays – radiation from space Rocks and soil – some rocks are radioactive and give off radioactive radon gas Living things – plants absorb radioactive materials from the soil and these pass up the food chain Tracers Radioisotopes are used as tracers in industry. These are used for tracking substances.: Find leaks or blockages in underground pipes Find the route of underground pipes Track the dispersal of waste Smoke detectors Smoke detectors alert people to fires. Smoke from the fire is detected by the device, which then gives off an alarm. One type of smoke detector uses americium-241, a source of alpha radiation, to detect smoke Dating rocks Radioactivity can be used to date rocks. Rocks often contain traces of uranium. This is unstable and eventually decays to lead, which is stable. The age of a rock can be calculated if its ratio of uranium to lead is known. The older the rock, the lower its uranium to lead ratio: Young rocks have a high uranium to lead ratio Very old rocks have a low uranium to lead ratio Artificial sources human activity has added to background radiation by creating and using artificial sources of radiation. These include radioactive waste from nuclear power stations, radioactive fallout from nuclear weapons testing medical x-rays. Higher tier Carbon-14 is a radioactive isotope. It is found in the air in carbon dioxide molecules. The amount of carbon-14 in the air has stayed the same for thousands of years. There is a small amount of radioactive carbon-14 in all living organisms because it enters the food chain. Once an organism dies, it stops taking in carbon-14. The carbon-14 it contained at the time of death decays over a long period of time, and the radioactivity of the material decreases.

Treatment Uses of radiation in medicine Sterilising equipment Tracers X-rays, gamma rays and beta particles are all used in medicine to treat internal organs. X-rays are produced by firing electrons at a metal target and gamma rays are emitted by the nucleus of radioactive atoms. Gamma rays are used to kill cancer cells, to sterilise medical equipment and in radioactive tracers. Uses of radiation in medicine Sterilising equipment . Tracers Tracers and treating cancer - Higher tier Tracers Treating Cancer

Treatment Uses of radiation in medicine Sterilising equipment Tracers X-rays, gamma rays and beta particles are all used in medicine to treat internal organs. X-rays are produced by firing electrons at a metal target and gamma rays are emitted by the nucleus of radioactive atoms. Gamma rays are used to kill cancer cells, to sterilise medical equipment and in radioactive tracers. Uses of radiation in medicine Sterilising equipment Gamma rays are high energy electromagnetic waves which are only stopped by thick lead. This means they can easily pass through medical equipment, such as syringes. Tracers Radioactive tracers are used to investigate a patient's body without the need for surgery. Gamma emitters beta emitters are used because gamma rays and beta particles can pass through skin, whereas alpha particles cannot. 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. Tracers and treating cancer - Higher tier Tracers Radioisotopes with short half-lives are chosen to make sure that the tracer does not stay radioactive in the body for long periods. The radioactive tracer is put into the body by one of the following ways: By an injection By ingestion Treating Cancer Gamma rays damage cells whether they are normal or cancerous, so gamma rays must be focused on the tumour. One way of doing this is to use a wide beam of gamma rays, but to rotate the beam around the patient, keeping the tumour at the centre. This concentrates the gamma rays on the cells that need to be killed.

Fission and Fusion Chain Reaction Higher Tier - Nuclear Fission Nuclear fission is the splitting of atomic nuclei. Nuclear power stations use the fission of uranium-235 to heat water. Fusion is the joining of atomic nuclei. Chain Reaction Higher Tier - Nuclear Fission 1. 2. 3. 4. Uranium is a energy resource and, like the fossil fuels, it cannot be replaced once it has all been used up. Nuclear fusion Higher Tier – Nuclear Fusion Cold fusion A group of scientists have claimed that they have achieved ‘cold fusion’ – nuclear fusion at ordinary temperatures and pressures. If it happens, cold fusion could be developed to provide almost limitless and cheap electricity. It would also make the international project to develop a fusion power station using high temperatures and pressures pointless.

Fission and Fusion Chain Reaction Higher Tier - Nuclear Fission Nuclear fission is the splitting of atomic nuclei. Nuclear power stations use the fission of uranium-235 to heat water. Fusion is the joining of atomic nuclei. Chain Reaction The fission of uranium can set up a chain reaction that will keep on releasing energy as long as there are uranium nuclei present. If this chain reaction is allowed to get out of control, energy is released very quickly and the result is a nuclear bomb. Nuclear power stations are designed to keep chain reactions under control Higher Tier - Nuclear Fission For fission to happen, the uranium nucleus must be hit by a neutron. When this happens: The nucleus splits into smaller nuclei, Energy is released and Two or three neutrons are released. Fuel produces heat, which is used to boil water to make steam. Steam spins a turbine. Turbine drives a generator and the generator makes electricity. Electricity goes to the transformers to produce the correct voltage. Uranium is a non-renewable energy resource and, like the fossil fuels, it cannot be replaced once it has all been used up. Nuclear fusion Nuclear fission is the splitting of large nuclei into smaller ones, while nuclear fusion is the joining of smaller nuclei to make larger ones. Nuclear fusion happens in stars and fusion bombs Higher Tier – Nuclear Fusion The Sun and other stars use nuclear fusion to release energy. The sequence of nuclear fusion reactions in a star is complex but overall hydrogen nuclei join to form helium nuclei. Cold fusion A group of scientists have claimed that they have achieved ‘cold fusion’ – nuclear fusion at ordinary temperatures and pressures. If it happens, cold fusion could be developed to provide almost limitless and cheap electricity. It would also make the international project to develop a fusion power station using high temperatures and pressures pointless.