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1. Slide 1: Science Interactive LTD Copyright 2005 Science Interactive LTD Science base multimedia CD-ROM for PC is a collection of 38 units or tools totalling over 1150 PowerPoint slides. Each unit covers a wide range of different delivery and learning styles, offering an exciting way to involve your pupils during lessons or revision sessions. All styles of teaching and learning are supported through use of high quality images, graphics, challenging exercises and questions. Units can be used in the classroom via an interactive whiteboard, data projector or used during individual study via a PC or school network. Science Interactive LTD. PO BOX 50764 LONDON NW6 9AT email: sales@science-interactive.co.uk web: www:science-interactive.co.uk Unit 1: The Digestive System Unit 20: Crude Oil and its Products Unit 2: The Circulatory System Unit 21: Rock Cycle Unit 3: Healthy Body and Immunity Unit 22: Elements, Molecules and Compounds Unit 4: The Respiratory System Unit 23: Ionic and Covalent Compounds Unit 5: Nervous System and the Senses Unit 24: The Halogens, their Uses and Compounds Unit 6: Human Homeostasis Unit 25: The Noble Gases, their Properties and Uses Unit 7: Hormones and the Endocrine System Unit 26: Rates of Reaction Unit 8: Drugs and Bad Body Maintenance Unit 27: Energy Unit 9: Photosynthesis in Green Plants Unit 28: Generating Electricity and its Domestic Use Unit 10: Water Transport in Plants Unit 29: Electricity Unit 11: Flow of Energy and Elements through the Environment Unit 30: Light and the Electromagnetic Spectrum Unit 12: Mitosis and Meiosis Unit 31: Radioactivity Unit 13: Inheritance and Selection Unit 32: Newton's Forces and the Effects of Forces Unit 14: Evolution and Human Impact Unit 33: Earth and Space Unit 15: Genetic Engineering Unit 34: The Earth and Plate Tectonics Unit 16: The Periodic Table and its Elements Unit 35: The Alkaline Earth Metals Unit 17: The Alkali Metals Unit 36: Sound and Hearing Unit 18: Metals and their Properties Unit 37: Natural Forces Unit 19: The Transitional Metals Unit 38: Cells, Tissue, Organs and Organs systems
2. Slide 2: Science Interactive LTD Copyright 2005 Unit 31  Radioactivity 
3. Slide 3: Unit 31: Radioactivity Science Interactive LTD Copyright 2005 Understand: Keywords: Radiation, Beta, Alpha Gamma, Rays, That there are three forms of radiation: alpha, 1. beta and gamma. Particles, Cloud, Chamber, Geiger, Muller, That radioactivity can be detected using different 2. Tube, Penetrating, Rutherford, Atomic, methods. Structure, Proton, Electron, Neutron, Isotopes, That alpha, beta and gamma radiation have 3. Unstable, Emission, Decay, Half life, Sources different properties. & Radioactivity. That their penetrating ability through materials 4. depends on their properties. How Rutherford used radioactivity to determine 5. the atomic structure of elements. That elements have isotopes, many of which are 6. unstable emitting alpha or beta particles or gamma rays when they break apart. How isotopes decay releasing either alpha or 7. beta particles or gamma radiation. That radioactive decay follows a half life. 8. Some of the uses of radioactivity. 9. Click mouse to begin Science Interactive LTD PO BOX 50764 LONDON NW6 9AT web: www.science-interactive.co.uk email: sales@science-interactive.co.uk
4. Slide 4: Science Interactive LTD Copyright 2005 Discovering radioactivity In the late 1800s, a French scientist called Becquerel discovered that some substances like Uranium235 altered p__________ film, even when the film was wrapped in black paper and placed in complete darkness. Becquerel called substances that affected film in this way radioactive. He also discovered that Uranium gives out r_________ at the same rate when hot or cold. Detecting radiation in nuclear power stations or in hospitals is very important so that workers are protected. There are four main ways in which we can detect radioactive emissions. Detecting radioactivity: Word bank: photographic radiation Method Photographic film GM Tube Electroscope Cloud chamber Diagram The photographic film The Geiger-Muller tube In an electroscope, the In a cloud chamber, a Notes shows how some of the is sensitive to radiation. air surrounding the ray from a radioactive film has been darkened A counter shows us how gold leaf is ionised by source causes a line of by emissions from many radioactive the radioactive source. ions on which a thin radioactive substances emissions are given out The gold leaves vapour trail forms. This except in the shadow of per second by becomes charged and is shown as white lines the key. radioactive sources. moves away. in the picture.
5. Slide 5: Science Interactive LTD Copyright 2005 Sources of radioactivity Radioactive substance and radiation is all around us and is called background radiation. Every single second of the day, our bodies are exposed to low levels of r___________. Sources of radiation can include the food and n_________ in our diet, the rocks we walk over, the air that we breath, the building materials that surround us and from cosmic rays emitted by sources far out in space. In Cornwall, radioactive Radon gas can seep into houses from deep underground. In high risk areas, residents have a higher risk of developing cancer. What are the other causes of cancer in humans e.g. smoking ? Sources of radioactivity: Word bank: radiation nutrients Air Radon gas Diet Cosmic rays Diagram The air we breath adds Radiation from medical Radiation from food and Cosmic rays are Notes about 60% to our X rays and nuclear drink account for about absorbed by our annual radiation dose. medicine accounts for 15% of your annual atmosphere, although it about 15% of your exposure to background still accounts for about Why can we not protect annual exposure to radiation. How does this 10% of annual ourselves from this background radiation. enter the food chain ? exposure. radiation ?
6. Slide 6: Science Interactive LTD Copyright 2005 The Geiger Muller tube The Geiger-Muller tube is the most commonly used detector of radioactivity from gamma, alpha and beta emitters. Inside the GM tube is a thin wire and a gas at very low pressure. Radiation from the radioactive source ionises this gas producing a pulse of electrical c________. This is then amplified to give an audible clicking s_______, each time a ray passes through the tube. It is also counted by a rate-meter which shows the radioactivity in ‘counts per second.’ Inside the Geiger Muller tube: Word bank: current sound GM tube Inside the GM tube Rate - meter Diagram Path of particle Meter Ionised tube Notes The GM tube with all its components including the ionising tube, circuitry, rate-meter and loudspeaker. Radiation from a radioactive source causes a current pulse to flow from the wire which is surrounded by a gas at very low pressure. This is amplified and passed to a rate-meter. A rate-meter allows us to compare how strong various radioactive sources are.
7. Slide 7: Science Interactive LTD Copyright 2005 Types of radioactivity The nature of all three types of radioactivity differs greatly. Alpha particles, for example are positively charged, containing four nucleons; two p_______ and two neutrons. Alpha radiation is easily stopped by paper. Gamma radiation is not affected by a magnetic field and is part of the electromagnetic spectrum. Gamma rays can even penetrate lead metal and thick concrete. Alpha, Beta and Gamma Radioactivity: Word bank: protons Radiation Alpha Beta Gamma Diagram Nature Helium nucleus Negative electron Electromagnetic wave Dangerous Yes Yes Yes Speed 10% speed of light 50% speed of light 100% speed of light Electric fields Yes Yes No Film Film Film Detectors     Cloud chamber  Cloud chamber  Cloud chamber  Gold leaf electroscope  GM Tube  GM Tube Gamma Alpha Thick lead 3mm Aluminium Beta Paper Penetrating ability Stopped Weakened Stopped
8. Slide 8: Science Interactive LTD Copyright 2005 Rutherford’s atomic structure Rutherford performed an experiment where he fired alpha particles at thin gold foil. Detectors were positioned at every angle to find how the a_______ particles were scattered or reflected by the gold atoms. It was discovered that some alpha particles were reflected back to the source – rather like firing a gun at tissue paper and finding some of the bullets bouncing back. He proposed that each atom had a tiny core or n_________ with a mass and a positive charge. This charge repelled the alpha particles. Rutherford's experiment: Word bank: alpha nucleus Rutherford’s experiment Rutherford’s experiment in detail Diagram Most particles are undeflected Alpha particles Gold atoms Notes Before Rutherford’s experiment the nature of the The atom’s ability to scatter alpha particles atom was unknown. It was thought that the mass demonstrated the presence of a nucleus with and charge was spread throughout the atom and a positive charge. The nucleus contains there was no nucleus. 99.99% of the atom’s mass.
9. Slide 9: Science Interactive LTD Copyright 2005 Atomic structure All atoms consist of three sub-atomic particles, neutrons, p________ and electrons. The simplest atom is hydrogen. Its nucleus contains a single proton with a single positive charge. There is a single electron in orbit of the positive nucleus. Because the charges are equal, but opposite, the atom is n________. It is the attraction between the electron and proton that holds the electron in it’s orbit. Helium has two protons and two uncharged particles called n_______ in its nucleus with two electrons held in orbit. Elements and sub atomic particles: Word bank: protons nucleus neutrons Hydrogen Helium Lithium Oxygen Diagram - - - - - - - + 3+ 8+ - 2+ + - - - - - - 1 4 7 16 H1 He 2 O Li 3 8 Two protons Proton _____________ ? _____________ ? _____________ ? Two electrons Electrons _____________ ? _____________ ? _____________ ? Two neutrons Neutrons _____________ ? _____________ ? _____________ ?
10. Slide 10: Science Interactive LTD Copyright 2005 Understanding isotopes of atoms Some elements like carbon and hydrogen have naturally occurring isotopes. Atoms of isotopes like hydrogen are made up of atoms of different m_______. The number of protons in isotopes of the same element is always identical, but the number of n________ is different. Isotopes of the same element have identical chemical properties, because their e__________ are arranged in the same way. Some isotopes are unstable emitting either alpha, beta or gamma radiation. How could we separate different isotopes of the same element ? Isotopes of atoms: Word bank: masses neutrons electrons Isotope Hydrogen Deuterium Tritium Common radioactive isotopes Diagram Isotope Symbol Radiation type 240 Pu 94 Plutonium240 Alpha 98 Technetium98 Gamma Te 52 Hydrogen Deuterium Tritium Neutrons 0 _____ ? 2 Uranium238 238 Alpha U 92 Protons 1 _____ ? 1 Radium228 Electrons 1 _____ ? 1 Beta 228 Ra 88 Electron 1 _____ ? 1 configuration
11. Slide 11: Science Interactive LTD Copyright 2005 Alpha decay An alpha particle is a helium nucleus with four nucleons: two protons & two neutrons. Pu240 decays by Alpha emission. When it loses an alpha particle its mass number of 240 must decrease by four to 236. Radium’s atomic number of 94 also decreases by two to become 92. Radium has changed by losing an alpha particle to form the new element: Uranium236. Alpha decay: Alpha decay Property Alpha radiation _______________? Diagram Nature Affected by electric _______________? fields Penetration Blocked by paper. Notes Plutonium240 loses a helium Dangerous Yes, if swallowed nucleus, 2 neutrons and 2 protons emitting an alpha Speed 10% speed of light. particle.
12. Slide 12: Science Interactive LTD Copyright 2005 Beta Decay A beta particle is an electron with almost zero mass and a negative charge. Radium228 decays by Beta emission. This is an emission of an electron from the nucleus. One of the neutrons in the nucleus changes into a proton and an electron is emitted. This means that there is an additional p_______ in the nucleus increasing the atomic number by one to 89. The mass number remains unchanged at 240. Radium has changed by one of its neutrons changing to form a proton and by emitting an electron to form the new element: Actinium228. Beta decay: Word bank: proton Beta decay Property Beta radiation _______________ ? Diagram Nature _______________ ? Affected by electric fields Penetration Stopped by 3mm aluminium Notes Dangerous Yes Radium228 decays by losing an electron by a neutron changing into a Speed 50% speed of light. proton.
13. Slide 13: Science Interactive LTD Copyright 2005 Gamma emission Gamma rays are waves - they are part of the electromagnetic spectrum like light and radio waves. They have a very short wavelength - smaller than an atom. They can pass through thick sheets of lead. They are very difficult to shield. When a radioactive isotope loses an alpha or beta particle it is left in an excited state. It loses this surplus energy by emitting a gamma ray. Gamma emission: Gamma emission Property Gamma radiation Diagram _______________? Nature Affected by electric fields No, uncharged Penetration Reduced but not stopped by lead or concrete. Notes Plutonium240* is an isotope Dangerous Yes in an excited state that emits excess energy by Speed 100% speed of light. emitting gamma rays.
14. Slide 14: Science Interactive LTD Copyright 2005 Uses of alpha radiation At home, in the kitchen or landing you might have a smoke detector. Inside the smoke detector is a very weak radioactive s_______ containing Americum241 which is an alpha emitter. Like all alpha radiation it causes the ionisation of air inside a detection chamber which in turn generates a small current flow. If smoke particles from a fire enters the air space between the radioactive source and the chamber it causes a reduction in the current. This then triggers an a_______. Why is a gamma source not used in smoke detectors ? Smoke detectors and alpha radiation: Word bank: source alarm Smoke detector Treating thyroid cancer Diagram Scan of a human thyroid following a radioactive dose of an alpha emitter (Iodine131) Notes If you have thyroid cancer, radioactive Smoke caused by fires alters the current flow inside a iodine is injected into the blood and is smoke detector, therefore triggering an alarm. This can absorbed by the thyroid. The alpha radiation provide an essential early warning system for those then destroys the cancer causing cells. How who live in the house, therefore saving many lives. does alpha radiation only destroy local cells in the thyroid ?
15. Slide 15: Science Interactive LTD Copyright 2005 Uses of Beta radiation During the manufacture of aluminium foil and sheet p_____, the thickness of the material can be controlled by using beta radiation. The amount of beta-radiation passing through the thin material is monitored by a Geiger-muller tube. The GM tube is connected to computer circuitry, which controls the amount of p________ exerted by rollers before and after. With thicker materials what kind of source should be used ? (Alpha, Beta or Gamma) Thickness control: Word bank: paper pressure radiation Thickness control of aluminium foil or paper Step Notes Radioactive source (beta) Diagram Beta particles penetrate and are 1 detected by the Geiger-Muller tube. Changes in paper or foil 2 thickness triggers a change in the amount of r________ detected by Paper th GM tube. Rollers The rollers responds and reduce 3 or increase the thickness of the foil or paper. GM tube Foil or paper is of desired 4 thickness. Machinery to control rollers
16. Slide 16: Science Interactive LTD Copyright 2005 Use of Gamma radiation one Gamma radiation is the most useful type of radiation and is used in many applications. It is also the most dangerous form of radiation to work with, because of its ability to penetrate materials including thick l_____ and concrete. The normal source for gamma radiation is Uranium235 a radioactive i_______. How would you monitor the radiation received by workers using gamma radiation ? Uses of gamma radiation: Word bank: lead isotope Use Radiotherapy Checking welds Checking cracks Diagram Notes In some cancers like breast The quality of metal welds Fatigue in metals and their cancer, cancerous cell are can be constantly checked welds can be imaged using irradiated using a gamma using gamma radiation. Film gamma radiation and source. The cells are killed by is used to image the weld. If photographic film. Explain the destructive nature of the the weld is poor, what will how the image is formed and gamma radiation. List the the film show along the weld why is light, beta or alpha possible side effects ? line ? radiation not used ?
17. Slide 17: Science Interactive LTD Copyright 2005 Use of Gamma radiation two Gamma rays from excited radioactive isotopes can be used to destroy m_______ including bacteria, present on the surfaces of foods like fruits and medical equipment. Food can be packaged and then irradiated, prolonging the shelf life of the food. This is completely safe as gamma rays cannot be absorbed into the fruit, but it can alter the taste of the food. Gamma rays are used by hospitals to s_________ heat sensitive products like blood and plastics. Why is the irradiation of fruit like strawberries currently not popular with the public ? Gamma rays and sterilisation: Word bank: microbes sterilise Blood Irradiated fruit Non-irradiated fruit Medical equipment Diagram Human blood products Fruit like strawberries Untreated fruit have a Plastics and surgical Notes are irradiated using are irradiated using short shelf life because tools are sterilised before gamma rays before gamma rays. This gives their surface is home to use during operations. transfusion into another them a longer shelf life, many surface microbes They cannot be steam patient. This destroys lasting up to seven days particularly bacteria sterilised because they any viruses. on supermarket shelves. which spoil the fruit. are heat sensitive.
18. Slide 18: Science Interactive LTD Copyright 2005 Use of Gamma radiation three In some cancers like breast cancer, cancerous cell are irradiated using a gamma source. The cells are killed by the destructive nature of the g_______ radiation. Furthermore, where surgery is impossible, radiotherapy can be used, although the success rate is not high. Killing all the cancerous c_____ whilst leaving healthy ones intact is very difficult, even for the most skilled surgeons. The survival rate for brain cancer remains low despite using radiotherapy. Explain why cancers are difficult to treat ? Irradiation using gamma rays: Word bank: gamma cells Locating the cancer Using radiotherapy to kill tumours Diagram Notes Here the brain cancer is Where surgery is impossible for example many brain tumours located using 3D imaging cannot be removed because of the surrounding tissue, techniques like MRI, CAT radiotherapy is the only option. The pictures above show how scans or more traditional X- using gamma rays, the cancer shrinks and then completely rays. disappears. What are the side effects of radiotherapy ?
19. Slide 19: Science Interactive LTD Copyright 2005 Radioactive Half-lives one Unstable isotopes like Uranium235 and Plutonium240 decay by emitting either alpha, beta or gamma radiation, forming new e__________ over time. The time taken for half the atoms to decay is called the half life of the substance. Half-lives of different isotopes vary, from fractions of a single second to many millions of years. Plutonium240 has a relatively short half life of 6500 years. Uranium235 has a relatively long half life of approximately 700 million years. Half-lives of radioactive isotopes: Word bank: elements Half lives Sodium24decay pattern Sodium24 half lives Diagram 1st half life 2nd half life 3rd half life Notes All atoms present are of the original Some radioisotopes have relatively short half lives. Sodium24 has a isotope e.g PU240. By the end of the half life of around fifteen hours Determine from the graph ? After a first half life only 50% of all atoms second half life, the activity has halved again, so that only 1/4 of the are the original isotope. By the end atoms survive. After 3 half lives, the number of radioactive atoms of the second half life only 25% of has halved again and only 1/8th survive. What fraction survives after the atoms are the original isotope. 4 & 5 half lives ?
20. Slide 20: Science Interactive LTD Copyright 2005 Inside a nuclear power station Electrical energy can be produced using nuclear energy. Increasingly, nuclear energy is used as an alternative to the combustion of fossil fuels including c______ oil and natural gas. This is partly because they are a finite resource and currently contribute to global warming because of c___________ dioxide emissions. A nuclear reactor uses Uraniun235 as a fuel source. These Uranium rods glow white hot, in turn heating water, producing s_______, which drives a turbine and generates e__________. Name three renewable ways of generating electricity ? Nuclear energy: Word bank: crude carbon steam electricity Power station Radioactive core Electricity Radioactive waste Diagram Notes A nuclear power station About 8% of our One problem is the Uranium235 rods glow with a characteristic electrical energy is radioactive waste and its white hot and heat water dome housing the produced using nuclear safe storage. It has to be turning it into steam. radioactive core. They fuels. In future years stored for up to 10,000 This drive the turbine are very expensive to this will rise as fossil years safely away from generators producing build and decommission. fuels decrease. humans. electricity.
21. Slide 21: Science Interactive LTD Copyright 2005 Generating electricity using nuclear power Using fossil fuels to produce electricity adds to acid rain and global warming. They are also non – renewable f_______ making it necessary to find alternative energy sources. A nuclear power station uses radioactive substances like Uranium as a fuel. As Uranium decays, huge amounts of energy is released which is then used to heat steam and drive t________ generators. Nuclear fuels are a highly concentrated energy source, with large nuclear power stations only requiring about 10 kg of nuclear fuel per day. The only problem is that radioactive waste materials need to be safely stored for many thousands of years. Generating and supplying electricity: Word bank: fuels turbine Diagram Nuclear power station Transformer 1 Overhead cables 400,000V Steam Fuel rods Generator 240V Turbine 33,000V Containment building Transformer 2 Transformer 3 Customer Steam produced from the energy given out during the radioactive decay of Uranium235 drives the Notes turbine and generator. A current is induced in the cables. Using nuclear fuels, although expensive does not produce any greenhouse gases like carbon dioxide or acid rain producing gases like sulphur dioxide. Radioactive waste and high decommissioning costs still limit their use here.
22. Slide 22: Science Interactive LTD Copyright 2005 Nuclear energy Generating electricity using nuclear energy raises a number of issues. Furthermore using isotopes like Uranium235 for nuclear w_______ and dealing with radioactive waste enjoys little support in Britain. There are many reasons ‘for and against’ using nuclear energy and Uranium235. The biggest argument for, includes reducing our use of f_______ fuels and that only a small percentage of background radiation comes from the nuclear power industry. List three reasons against using nuclear fuels for generating electricity ? Nuclear energy: Word bank: weapons fossil Nuclear weaponry Nagasaki Radiation sickness Three-mile island Diagram During testing of In Japan, during WWII, Receiving high doses Three-mile island in the Notes nuclear weapons and America dropped two from gamma radiation US was a nuclear power warheads, US soldiers ‘Atom bombs’ on can lead to death and station. A coolant failure were asked to ‘witness’ Japan. The photograph radiation sickness. led to a ‘meltdown’ and the bombs close to the shows Nagasaki in After the initial death an explosion in the testing site. Many have complete ruins just toll in Japan up to reactor. The radioactive since died prematurely hours after the bomb 500,000 people died cloud affected a huge from various cancers. dropped. within 10 years. area.
23. Slide 23: Science Interactive LTD Copyright 2005 Radioactive dating one As time moves forward, the amount of radioactive Uranium235 has gradually decreased in the Earth’s rocks, changing slowly into stable lead. Because we know the h_____ life of Uranium235 (700 million years), by measuring the ratio of Uranium235 and lead in a rock sample, we can determine its a_____. Geologists use these methods to age rock samples from Earth, as well as meteorites from other planets including Mars. Using this method, scientists have dated the age of Earth and Mars at about 4.5 billion years. Radioactive dating: Word bank: half age Uranium235 decay to lead206 Earth’s age Diagram alpha beta gamma 700 million years Uranium235 Lead206 The age of the Earth is Notes Uranium235 transmutes or changes through 14 different isotopes around 4.5 billion years. finally producing stable lead, with a half life of 700 million years. We know this because of Decay sequence: radio dating of rocks. Uranium236 Thorium234 Protactinium234 Uranium234 Created at the same times as Mars and probably the Thorium230 Radium226 Radon222 Polonium218 Lead214 other seven planets. Bismuth210 Polonium210 Lead206.
24. Slide 24: Science Interactive LTD Copyright 2005 Radioactive dating two All living organism contain carbon. Most of the c________ in your body and tissues is stable carbon12. Another form or isotope of carbon is carbon14 with a half life of 5700 years. While the amount of carbon14 in the living human body remains constant, after your death, the amount of carbon14 decreases by half every 5700 years. Using this method we can find the time of d_______ for organisms up to 60,000 years ago. Why is the carbon14 method not suitable for dating rocks ? Radiocarbon dating: Word bank: carbon death Carbon14 The Shroud of Turin Dating cloth Diagram - - - - - - Carbon 14 Notes Carbon14 is an unstable Using the Carbon-14 method, the age of Other organic materials form of carbon with a the ‘Shroud of Turin’ a cloth believed to like cloth and remains of half life of 5700 years. It have wrapped the body of Jesus around dead organisms can be is present in the 33 AD was proved to be a fake, dated at dated using this method. atmosphere (in CO2) only 600 years old.
25. Slide 25: Science Interactive LTD Copyright 2005 Radioactive dating three All living organisms contain carbon. Very small amount of the carbon found in plant and animal tissues is the unstable isotope, carbon14. The levels of carbon14 remain constant during an organism’s life. When an o_________ dies, the unstable carbon14 begins to decrease with half the unstable atoms remaining after 5700 years. Comparing the ratio of carbon14 to carbon12 can give scientists an accurate age of a fossil. Another advantage is that you only require a very small sample for t_________. Why is this important when you are dating valuable artefacts like the ‘Shroud of Turin.’ Carbon dating: Word bank: organism testing Living organism Fossil Key Diagram Carbon 14 Carbon 12 Carbon14: Carbon12 Notes: The amount of carbon14 begins to reduce from death onwards. Comparing the ratio of unstable carbon14 to stable carbon12 gives us an accurate age of fossil or material.
26. Slide 26: Science Interactive LTD Copyright 2005 Extension questions and homework 1: Define the following terms: Radiation, Beta, Alpha, Gamma, Proton, Electron, Neutron, Isotopes, Unstable, Emission, Decay, Half-life, Radioactivity. 2: Look at the three pictures. Complete the table. Picture Application Type of radioactivity used Explanation One Radiotherapy Two Sterilisation Three Smoke alarm 3: Answer the following: a) Most of the carbon in your body and tissue is carbon12 (C12 ) Draw a dot and cross of this atom. b) Another form or isotope of carbon is carbon14 (C14 ) with a half life of 5700 years. What fraction of carbon14 is left after 2825 years. c) While the amount of carbon14 in the human body when you are alive remains constant, after your death, the carbon14 decays with a half life of 5700 years. Imagine your bones gives a reading of 70 mSV-1 using a Geiger- muller tube and an fossilised bone gives a reading of 20 mSV-1. What is the age of the old bone.
27. Slide 27: Science Interactive LTD Copyright 2005 4: Look at the information in the table below. It shows the decay of radium over time. Time (year) 2000 2800 3600 4400 5200 6000 6800 7600 8400 Mass (g) 100 50 ? 12.5 ? ? ? ? ? a) Complete the table for mass of radium. b) Plot time (x) against mass left on graph paper. c) Work out when you would have 30 g and 10 g of radioactive radium in the lab. d) Draw a decay scheme for radium. e) Mark each half life on the x axis. 5: a) Give two different uses of alpha, beta and gamma radiation. b) Strontium90 has a half life of 28 years. It is a beta emitter and may be absorbed by human bone tissue. How much time would pass before the activity falls to 1/32nd of its original value. c) Explain why workers at a nuclear factory wear badges containing unexposed photographic film that is checked every week. 6: Complete the following table: Item Nature Charge Sources Alpha particle Beta particle Gamma ray Internet: Go to google.co.uk and find out about carbon dating and the Shroud of Turin. Explain how scientists disproved the theory that this was the piece of cloth that wrapped Jesus' body after his death.