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February 2016 © Copyright The PiXL Club Ltd, 2016 This resource is strictly for the use of member schools for as long as they remain members of The PiXL Club. It may not be copied, sold nor transferred to a third party or used by the school after membership ceases. Until such time it may be freely used within the member school. All opinions and contributions are those of the authors. The contents of this resource are not connected with nor endorsed by any other company, organisation or institution. www.pixl.org.uk The PiXL Club Ltd, Company number 07321607

How to deliver the DDT Booster Administer the short diagnosis test. Mark the test. Work through the therapy slides completing the model questions and answers. Complete the question slides for students to self or peer assess. Administer the final test.

Conduction and convection Edexcel Additional Radioactivity P2.5 P2.6 – Nature of Radioactivity Model Questions A Uranium isotope has an atomic number of 92 and a mass of 236. How many protons and neutrons does it have? If the above isotope loses an alpha particle, what will its new atomic number and mass be? Why is an alpha particle often described as a Helium nucleus? Model Answers 92 protons, 144 neutrons Atomic number = 90, mass = 232 An alpha particle is made of 2 protons and 2 neutrons, the same as the nucleus of a Helium atom. Types of Radioactivity In some types of atom, the nucleus is unstable, and will decay into a more stable atom. This is radioactive decay. When an unstable nucleus decays, there are three ways that it can do so. It may give out:- an alpha particle (we use the symbol α) a beta particle (symbol β) a gamma ray (symbol γ ). Alpha particles are made of 2 protons and 2 neutrons. Beta particles have a charge of minus 1. This means that beta particles are the same as an electron. Gamma rays are waves, not particles. This means that they have no mass and no charge. CLICK to reveal MODEL ANSWER P1.1.3a/P1.1.1

Conduction and convection Edexcel Additional Radioactivity P2.5 P2.6 – Properties of Radioactivity Model Questions Smoke alarms contain an alpha emitting isotope. Why are these alarms not dangerous for household use? An isotope has a count rate of 240cts/min. 30 years later the count rate is 60cts/min. What is the half life of the isotope? Model Answers Alpha particles do not travel far in the air and do not penetrate the skin. 240 to 60 = 3 half lives Half life = 10 years. Different radioactive emissions have different penetrating powers. The rate of radioactive decay can not be changed. A measure of how quickly an isotope decays is measured by its half life. Half life – the time it takes a radio isotope to lose half its radioactivity. The amount of radioactivity emitted is measured using a Geiger Muller tube. This measures count rate e.g. counts per minute (cts/min). http://www.darvill.clara.net/nucrad/types.htm CLICK to reveal MODEL ANSWER P1.1.3a/P1.1.1

Conduction and convection Edexcel Additional Radioactivity P2.5 P2.6 – Half Life Model Questions. 1. Carbon-14 has a half-life of 5 700 years. If an archaeologist discovers that an object has one eighth of the radioactivity due to Carbon-14 that it originally had, how old is the object? Use the graph opposite to calculate the half life of the radioactive isotope. Model Answers One eighth = 3 half lives. 3 x 5700 = 17 100 years old. 40 Counts = 2 days half of this = 20 counts = 4 days. 4 – 2 = 2 days half life. Half life – the time it takes a radio isotope to lose half its radioactivity. Half life can be found from a decay curve graph or by calculation. To calculate half life you need to remember that the sequence progresses: 1 1 1 1 etc 2 4 8 16 CLICK to reveal MODEL ANSWER P1.1.3a/P1.1.1

Conduction and convection Edexcel Additional Radioactivity P2.5 P2.6 – Half Life Uses of radioactivity include smoke alarms, irradiating food, sterilizing equipment, thickness measurement and medical uses. Uses of alpha radiation Ionisation is useful for smoke detectors. Americium ionises the air inside the detector. Smoke absorbs alpha radiation, altering the ionisation and sounding the alarm. Uses of beta radiation Tracers and monitoring the thickness of materials. Doctors use radioactive tracers for medical imaging. Radiation is used in industry in detectors that monitor and control the thickness of materials such as paper, plastic and aluminium. Uses of gamma radiation Gamma radiation is used in the treatment of cancer, testing equipment and sterilising medical instruments. Model Questions. Why is alpha radiation used in smoke detectors? Why is gamma radiation used to treat cancer. Model Answers Alpha particles are efficient ionisers of the air and do not travel far, keeping the used safe. Gamma radiation kills cancer cells. It can also penetrate deep into the body. It also kills healthy cells so low doses from different directions have to be used. CLICK to reveal MODEL ANSWER P1.1.3a/P1.1.1

Conduction and convection Edexcel Additional Radioactivity P2.5 P2.6 – Radioactive safety Model Questions. When treating someone with cancer, gamma radiation is used. Why is this safer than using alpha or beta particles What is “background radiation”? Why is high level waste often stored underwater? Model Answers Gamma is less ionising so is less likely to cause damage to healthy cells. The radiation always present from rocks, water, buildings and some put into the environment by humans. Often nuclear waste which generates a lot of heat. The main danger from radioactivity is the damage it does to the cells in your body. When Alpha or Beta particles pass another atom, they tend to pull electrons off it. We then say that the atom is ionised. The amount of radiation received determines the risk. This is called dose. Waste has to be disposed of carefully. Alpha Least penetrating High ionisation Beta Moderate penetration Moderate ionisation Gamma Highly penetrating Least ionising CLICK to reveal MODEL ANSWER Level of waste Disposal method High Often vitrified, sealed in steel drums and stored underwater Medium Mixed with cement, sealed in drums and stored underground. Low Placed in landfill sites P1.1.3a/P1.1.1

Conduction and convection Edexcel Additional Radioactivity P2.5 P2.6 – Nuclear power Model Questions. What is meant by a “chain reaction”? What are the products of nuclear fission of Uranium 235? Which of the two nuclear processes opposite occurs in the sun? Model Answers An uncontrolled reaction where the products promote the spread of the reaction. Krypton, Barium, neutrons and energy. Nuclear fusion. Nuclear energy relies on the energy released when an isotope is split (fission). This can be shown as a nuclear formula: The three neutrons produced from one disintegration can split another three Uranium atoms, creating a chain reaction. To prevent a chain reaction, Boron rods are inserted between the fuel rods. These soak up excess neutrons. Fusion is the joining of atoms to release energy CLICK to reveal MODEL ANSWER P1.1.3a/P1.1.1

P2.5 P2.6 Radioactivity - Questions What is an isotope? Complete the alpha decay reaction for Uranium235: What is meant by nuclear fission? Iodine 131 has a half life of 8 days. After24 days what fraction of the original radiation will remain? Why do people who work in radioactive environments wear blue badges?

P2.5 P2.6 Radioactivity - Answers What is an isotope? Atoms of the same element but with different atomic masses due to varying numbers of neutrons. Complete the alpha decay reaction for Uranium235: What is meant by nuclear fission? A nuclear reaction where a heavy isotope splits into new elements. Iodine 131 has a half life of 8 days. After24 days what fraction of the original radiation will remain? 24 days = 3 half lives. Three half lives means one eighth will remain. Why do people who work in radioactive environments wear blue badges? The badge detects the radiation dose so warn the wearer when they have reached the maximum safe working dose of radiation. They can then remove themselves from any danger. 4 90

Final test DTT Booster Students now complete the final test. Compare this to what they achieved in the diagnostic test.