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  • 1. P6 Radioactive materials254
  • 2. P6: Radioactive materialsWhy study radioactivematerials? People make jokes about radioactivity. If you have hospital treatment with radiation, they may say you will ‘glow in the dark’. People may worry about radioactivity when they don’t need to. Most of us take electricity for granted. But today’s power stations are old. Should nuclear power stations be built as replacements? Should we research nuclear fusion as a long-term energy solution?What you already know The Science• Some materials are radioactive, and naturally The discovery of emit gamma rays. radioactivity changed ideas about matter and• Gamma rays are ionising radiation. atoms. The nuclear model• Ionising radiation can damage living cells. of the atom helped• Nuclear power stations produce radioactive scientists explain many waste. observations – including radioactivity and the• Contamination by a radioactive material is colour of stars. more dangerous than a short period of irradiation. Ideas aboutFind out about Science• radioactive materials and emissions Physicists’ understanding of radioactivity has• radioactive materials being used to treat enabled them to develop cancer many applications – from• ways of reducing risks from radioactive nuclear power stations materials to cancer detection and treatment. Knowledge of• nuclear power stations and fusion research. radioactivity is essential to develop safe ways of working. 255
  • 3. A Radioactive materials What do these elements have in common? Find out about D radioactive decay D what makes an atom radioactive D types of radiation Radon is a radioactive gas. Radium is a radioactive metal. in the early 1900s, these bulbs were used to make drinking water radioactive. uranium ore – uranium is used as a nuclear fuel in power stations. They are all radioactive. If you test them with a Geiger counter you will hear it click. When radioactivity was first discovered, people did not know that the radiation was ionising and could damage or kill living cells. They thought that it was natural and healthy. Manufacturers this scientist is measuring made all kinds of products using radioactive materials. When the radioactivity of the fruit scientists realised the danger the products were banned. from plants grown with radioactive water. Safety rules for using radioactive materials were introduced. Radioactive elements can be naturally occurring, or they can be man-made. The man-made elements may be produced because they are useful. For example, the radioactive hydrogen in the water molecules is used to water the plants in the photograph. They may be a waste product, like waste from nuclear power stations.256
  • 4. P6: Radioactive mateRialsChanges inside the atomMany elements have more than one type of atom. For example, some carbon atoms are radioactive. In most ways they are identical to other carbon atoms. All can:• be part of coal, diamond, or graphite• be a part of molecules• take point in chemical reactions, for example, burn to form carbon dioxide. a cut diamond sitting on a lump of coal. each of these isRadioactive decay made of carbon atoms. some of the atoms will be radioactive.The main difference is that most carbon atoms do not change. They are stable. Radiation What it isRadioactive carbon atoms randomly give out energetic alpha small, high speedradiation. Each atom does it only once. And what is left particles particle withafterwards is not carbon, but a different element . The process (␣) ϩ chargeis called radioactive decay. It is not a chemical change; it is a beta smaller, higherchange inside the atom. particles speed particle with (␤) Ϫ chargeWhat makes an atom radioactive? gamma high energy radiation electromagneticAtoms have a tiny core called the nucleus. In some atoms, the (␥) radiationnucleus, is unstable. The atom decays to become more stable. It emits energetic radiation and the nucleus changes. This is why the word ‘nuclear’ appears in nuclear reactor, nuclearmedicine, and nuclear weapon.Three types of radiation are emitted, called alpha, beta, and gamma. Questions Summary box 1 how can you test to see if something is radioactive? D Some atoms are 2 Why is ionising radiation dangerous? radioactive. They decay by emitting 3 What are the three different types of radiation from alpha particles or radioactive materials? gamma radiation. A: Radioac tive mateRials 257
  • 5. B Atoms and nuclei How do scientists know about the structure Find out about of atoms? DDmodels of the atom The ‘solar system’ model of the atom dates back to 1910, and DDhow alpha particle an experiment thought up by Ernest Rutherford. Scientists scattering reveals were beginning to understand radioactivity, and were the existence of the experimenting with radiation. Rutherford realised that alpha atomic nucleus particles were smaller than atoms, and so they might be useful tools for investigating the structure of atoms. So he designed a suitable experiment, and it was carried out by his assistants, Hans Geiger and Ernest Marsden. Here is how to do it: • Start with a metal foil. Use gold, because it can be rolled out very thin, to a thickness of just a few atoms. • Direct a source of alpha radiation at the foil. Do this in a vacuum, so that the alpha particles are not absorbed by air. • Watch for flashes of light as the alpha particles strike the detecting material on the screen at the end of the microscope. The ‘solar system’ model of • Work all night, counting the flashes at different angles, to the atom has a nucleus at see how much the alpha radiation is deflected. the centre and electrons whizzing around like miniature planets. gold foil screen microscope alpha source Rutherford’s experiment. An alpha particle striking the detecting material gives a tiny flash of light.258
  • 6. P6: Radioactive materialsResults and interpretation most radiationThis is what Geiger and Marsden observed: alpha radiation only slightly• Most of the alpha particles passed straight through deflected back-scattered the gold foil, deflected by no more than a few degrees. gold foil• A few of the alpha particles were actually reflected back towards the direction from which they had come.And here is what Rutherford said:‘It was as if, on firing a bullet at a sheet of tissue paper,the bullet were to bounce back at you!’In fact, very few alpha particles were back-scattered, butit still needed an explanation. alpha radiation gold nucleusRutherford realised that there must be something withpositive charge repelling the alpha particles becausethey also have positive charge. And it must also have alot of mass, or the alpha particles would just push it outof the way. Only alpha particles passing closeThis ‘something’ is the nucleus of a gold atom. It contains all of to a nucleus are deflected by athe positive charge within the atom, and most of the mass. large amount.Rutherford’s nuclear model is a good example of a scientist usingcreative thinking to develop an explanation of the data.His analysis of his data showed that the nucleus was very tiny,because most alpha particles flew straight past without beingaffected by it. The diameter of the nucleus of an atom isroughly a hundred-thousandth of the diameter of the atom. Questions 1 What charge do the following have: a the atomic nucleus? b alpha radiation? Summary box c electrons? DDThe alpha particle experiment should 2 Put these in order, from least mass to greatest: gold that atoms have a atom, alpha particle, gold nucleus, electron. small massive nucleus with 3 Describe and explain what happened to alpha particles positive charge. that were directed: DDRutherford used a straight towards a gold nucleus creative thinking to b slightly to one side of a gold nucleus develop the nuclear c midway between two nuclei. model explanation. B: Atoms and nuclei 259
  • 7. C Inside the atom Atoms are small – about a ten millionth of a millimetre across. Find out about Their outer layer is made of electrons. Most of their mass is D protons and concentrated in a tiny core, called a nucleus. neutrons D ␣ and ␤ particles The nucleus The tiny nucleus contains two types of particle: protons and neutrons. Carbon-11 and carbon-12 are different forms of carbon. Carbon-12 has 12 particles in the nucleus: six protons and six neutrons. Carbon-11 has 11 particles in the nucleus: six 6p protons and five neutrons. These different forms are called 6p 6n 5n isotopes of carbon. Carbon-11 will give out its radiation whether it is in diamond, coal, or graphite. You can burn it or vaporise it and it will still carbon-12 carbon-11 be radioactive.6p 6p6n 5non-12 carbon-11 carbon-11 has 11 particles in its compared to the nucleus: 6 protons and 5 neutrons. whole atom, the tiny the nucleus of carbon-12 has 6 nucleus is like a protons and 6 neutrons. pinhead in a stadium. Making gold When radioactive platinum decays it turns into a new element – gold. A good way to make money? No. The price of gold is only half the price of platinum. beta radiation 260
  • 8. P6: Radioactive materialsRadioactive changesSome nuclei that are unstable can become more stable byemitting an alpha particle.Other nuclei can become more stable by emitting a betaparticle. These particles come from the nucleus of the atom. ␥ ␣ ␤ It is the nucleus of an atom that makes it radioactive and emits the radiation.The emission of either an alpha or a beta particle from anunstable nucleus produces a nucleus of a different element,called a ‘daughter product’ or ‘decay product’. The daughterproduct may itself be unstable. There may be a series ofchanges, but eventually a stable end-element is formed. Questions 1 Look at these nuclei: A carbon-11 B boron-11 C carbon-12 D nitrogen-12 a Which two are the same element? Summary box b Which ones have the same number of particles in DDAlpha or beta the nucleus? particles are emitted c Do any of them have identical nuclei? by an unstable 2 Put in order of size with the biggest first proton, atom, nucleus. DDThis produces a nucleus, molecule, pinhead. nucleus of a 3 What part of the atom does the radiation come from? different element. C: Inside the Atom 261
  • 9. D Using radioactive isotopes Radioactive isotopes have many uses, but they are quite Find out about rare in Nature – because most of them have decayed – so DDalpha, beta and radioactive isotopes are made in nuclear reactors for use in gamma radiation laboratories and hospitals around the country. DDsterilisation using ionising radiation Alpha, beta or gamma? To decide which radiation to use, scientists consider these properties. Alpha radiation Alpha particles are much heavier than beta particles, and they quickly collide with air molecules and slow down. This means that they are the least penetrating, but also the most strongly ionising radiation. They are stopped most easily. invisible nuclear radiation Beta radiation Beta particles move very fast. They are much smaller than alpha particles so less alpha likely to collide with other particles. beta lead gamma This means they travel further in aluminium air and other materials and are less ionising. paper Uses of ionising radiations are linked to their properties. Gamma radiation Sometimes, the protons and neutrons in the nucleus just rearrange themselves to become more stable. Question When this happens the nucleus emits a photon of electromagnetic radiation called a gamma ray. 1 Which type of radiation: a is the most penetrating? This does not cause a change of element. b is the most ionising? The photons have more energy than most X-ray photons and rarely collide with particles, so the c has the longest radiation is very penetrating. It has only a range in air? very weak ionising effect.262
  • 10. P6: Radioactive mateRialsProperties of ionising radiationradiation range in air stopped by ionisation chargealpha a few cm paper / dead strong ϩ skin cells The logo shows that thebeta 10–15 cm thin aluminium weak Ϫ herbs and spices have been irradiated with gammagamma many thick lead or very weak no charge radiation from Cobalt–60. metres several metres Gamma rays pass through of concrete the glass and kill any bacteria in the jar. Cobalt–60 does not pass in to the jar– thereSterilisation is no contamination.Ionising radiations can kill bacteria. Gamma radiation is used for sterilising surgical instruments and some hygiene products such as tampons. • The products are first sealed from the air and then exposed to the radiation. uses of ionising radiation are• This passes through the sealed packet and kills the bacteria linked to their properties. inside. Food can be treated in the same way. Irradiating food kills bacteria so the food lasts longer. Since 2010, irradiation is permitted in the UK for herbs and spices. The label must show that they have been treated with ionising radiation. This can be better than heating or drying, because it does not affect the taste. Questions 2 a Why seal the packets of surgical instruments before gamma rays kill the bacteria sterilising them? on and inside these test tubes. b does the gamma radiation make them radioactive? explain your answer. 3 smoke detectors used in homes contain a source that Summary box D Alpha, beta, and emits alpha particles. gamma radiations a explain why these are not dangerous in normal use. have the different b What might make them dangerous? properties described above. D Gamma radiation is used to sterilise food and surgical products. D: using Radioac tive isotoPes 263
  • 11. E Radiation all around Radiation sources Find out about If you switch on a Geiger counter, you will hear it click. It is DDbackground picking up background radiation, which is all around you. radiation Most background radiation comes from natural sources. DDa radioactive gas Natural 84% called radon DDradiation dose 50% radon gas and risk from the ground 9.5% from food and drink 13% gamma rays from 12% 15% the ground and cosmic rays medical buildings How different sources contribute to the average radiation dose in the UK. Source HSE 0.1% nuclear discharges 0.1% products 0.2% fallout 0.2% occupational The UK average annual dose is Artificial 16% 2.5 mSv. Radiation dose Questions Radiation dose measures the possible harm the radiation could do to the body. It is measured in millisieverts (mSv). 1 a In what units is • The UK average dose is 2.5 mSv a year. radiation dose • With a dose of 1000 mSv (400 times larger) three out of a measured? hundred people, on average, develop a cancer. b What is the average radiation dose per Ionising radiation from outer space is called cosmic radiation. year in the UK? • Flying to Australia gives you a dose of 0.1mSv, from cosmic c What percentage of rays. That’s not much if you go on holiday, but it soon adds the average up for flight crews. radiation dose in the UK comes from food and drink? What affects radiation dose? The dose measures the possible harm done by the radiation. It 2 a How big a dose of depends on: radiation do you get • the amount of radiation reaching the body by catching a flight • the type of radiation. Alpha is the most ionising of the three to Australia? radiations. So it can cause the most damage to a cell. The b Where do cosmic same amount of alpha radiation gives a bigger dose than rays come from? beta or gamma radiation.264
  • 12. P6: Radioactive mateRialsThe damage to the body depends on the type of tissue affected. Lung tissue is easily damaged. Radon gas is dangerous because it emits alpha particles. If it is breathed into the lungs then the alpha radiation will be absorbed in the lung tissue.Is there a safe dose?There is no such thing as a safe dose. Just one radon atom might cause a cancer. This is like a person being knocked down by a bus the first time they cross a road. The chance of it happening is low, but it still exists. The lower the dose, the lower the risk. But the risk is never zero.IrradiationIrradiation is when you are exposed to a radiation source outside your body. Alpha irradiation presents a very low risk because alpha particles:• only travel a few centimetres in air• are easily absorbed.Your clothes will stop alpha particles. So will the outer layer of dead cells on your skin. in the 1970s, alice stewart’s research suggested that radiation is more harmfulIrradiation by beta particles is more risky as they to children and to elderly people. she waspenetrate a few centimetres into the body. attacked for her ideas.Most gamma rays pass straight through the body. They have high energy, so if they are absorbed they are dangerous.ContaminationContamination is when a radiation source enters your body, or gets on your skin or clothes. You become Summary boxcontaminated. If you swallow or breathe in any D Radiation dose isradioactive material, your organs will be exposed to affected by:continuous radiation. Sources that emit alpha particles  amount ofare the most dangerous because alpha particles are the radiation  type of radiation.most ionising. Contamination by gamma sources is the D Radiation dose isleast dangerous as most gamma rays will pass straight measured inout of the body. millisieverts (mSv). E: Radiation all aRound 265
  • 13. Radiation protection Health physicists study radiation hazards and give advice to protect against them. They also keep a close eye on people who work with radioactive materials, for example, in hospitals, and industry. These people are called ‘radiation workers’. Employers must ensure that radiation workers receive a radiation dose ‘as low as reasonably achievable’. For example, if better equipment would reduce the risk, and the cost is reasonable, they must buy it. There is guidance to protect hospital patients who receive radiation treatment too. If one hospital uses smaller doses but its results are just as good, then all hospitals are asked to copy them. Working with radiation Manisha is a nuclear medicine technician in a hospital. She prepares radioactive isotope doses and may be exposed to radiation. To keep her dose low she: • uses protective clothing and screens • wears gloves and an apron • wears a personal radiation monitor whenever she is working. staff handle radioactive sources Questions with gloves and forceps. 3 on what two factors does radiation dose depend? 4 explain the difference between irradiation and contamination. 5 explain how each of the precautions manisha takes helps her to keep her radiation dose as low as possible. People working with radiation wear a personal radiation monitor to keep track of their dose.266
  • 14. Living with radon FRadon gasOver 400 years ago, a doctor wrote about the high death rate Find out aboutamongst German silver miners. He thought they were being D radon gaskilled by dust, causing disease. D radiation doseWe now know that radon gas is harmful because it is and riskradioactive. It produces ionising radiation that can damage cells. The silver miners were dying of lung cancer. Radon gas escapes from rocks.Radon and lung cancer Radon is breathed in. The miners are contaminated.Radon seeps into houses in some areas of the UK, as described in the leaflet on the following page. Scientists have done lots of studies to see if a low dose over a long time increases the risk of lung cancer.Scientists measure radon levels in the homes of people with lung cancer and compare them with levels in homes of people silver mines were contaminatedwho have not got lung cancer. One study: with radon gas. the miners• chose women who had lived in the same homes for 20 years breathed it in and suffered.• compared 413 women with lung cancer with 614 without lung cancer• showed a link between radon exposure and lung cancer. the pipe runs beneath the floorSome studies have not shown a link. This may be because: of the house and a small fan sucks the radon from the building.• they had a smaller sample size• it is difficult to measure radon exposure over time, especially if people move. Question 1 a What was the correlation that the doctor observed? b What was i) the factor and ii) the outcome in what happened to the silver miners? F: living With Radon 267
  • 15. A hazard at home Radon gas builds up in enclosed spaces. In some parts of the UK, it seeps into houses. LIVING WITH RADON GOVERNMENT INFORMATION LEAFLET There is radon all around you. It is radioactive and Radon information can be hazardous – especially in high doses. Percentage of homes where Visit www.hpa.org 7 radon levels are too high. or write to: 0–1 5–10 Radon Survey, NRPD Radon gives out a type of ionising radiation called 1–3 10–30 Chilton greater DIDCOT 3–5 alpha radiation. Like all ionising radiations, alpha than 30 OX11 0RQ 6 radiation can damage cells and might start a cancerous growth. Radon is a gas that can build up in enclosed 5 spaces. Some homes are more likely to be contaminated with radon. 4 What about my home? 3 You and your family are at risk if you inhale radon- contaminated air. The map shows the areas where 2 there is most contamination. If you live in one of these areas, get your 1 house tested for radon gas. 4 5 6 2 3 What if the test shows radon? Radon-affected areas in england and Wales. Based Radon comes from the rocks underneath some on measurements made in over 400 000 homes. buildings. It seeps into unprotected houses through the floorboards. If your house Not adapted is contaminated, get it protected. An Adapted approved builder will put in: • a concrete seal to keep the radon radon gas dispersed under your floorboards and • a pump to remove it safely. radon gas in house The risk is real: put in a seal. fan wooden floor wooden floor concrete pipe hardcore sump Radon gas can build up inside your home. sealing the floor and pumping soil out the gas is an effective cure.268
  • 16. P6: Radioactive mateRialsRadon and riskThe risk to miners was high because radon can build up in Questionsenclosed spaces, such as mines. In the atmosphere, the radon 2 there is a risk fromspreads out. In mines the rocks keep producing the gas and it radon gas building upcannot escape. So the radon concentration can be 30 000 times in houses. Which ofhigher than in the atmosphere. these are good ways to reduce the risk?There is a lower concentration in a house. And it is much lower • stop breathingif the windows are open or there are draughts. • wear a special gasOn average, radon makes up half the UK annual radiation maskdose. About 1100 people die each year from its effects. That is • move houseabout 1 in every 50 000 people. Radon is only one hazard. There • adapt the house.are risks with driving to school, sunbathing, swimming, and 3 choose three causes ofeven eating. death from the table on the left. Write downMany risky activities have a benefit. You need to decide a way of reducing thewhether to take the risk. risk from each one.The table shows how the risk of cancer from radon compares 4 Write a letter to a friendwith some other common risks. living in a high-radon area to persuade themCause of death Average number of deaths per year to get their housecancer caused by radon 1100 checked for radon.cancer among workers 4000caused by asbestos Summary boxskin cancer caused by 1400ultraviolet radiation D Ionising radiation can damage livingroad deaths 2500 cells. This may causecancer caused by smoking 35 000 cancer. D Radioactive materialscJd 98 may irradiate orhouse fire 360 contaminate people. D The risk depends onall causes 510 000 the radiation dose. estimated deaths per year in the uK population of 60 million (2008). F: living With Radon 269
  • 17. G Half-life Radioactive decay is random. You can never tell which nucleus Find out about will decay next. Scientists can’t predict whether a particular DDthe half-life of nucleus will decay today or in a thousand years time. But in a radioactive sample of radioactive material there are billions of atoms, so materials they can see a pattern in the decay. The pattern of radioactive decay The amount of radiation from a radioactive material is called its activity. This decreases with time. • At first there are a lot of radioactive atoms. • Each atom gives out radiation as it decays to become more stable. • The activity of the material falls because fewer and fewer radioactive atoms remain. Half-life Technetium-99m is a radioactive element used as a medical tracer. The diagram shows what happens when it is injected into a patient at 9:00 am. am t9 r ta a St 6 hours 6 hours 6 hours later later later Another half have Another half gone This is the sample half of the nuclei decayed – only a have decayed ​ 1 now only __ ​ left 8 of radioactive quarter are left nuclei injected 1 Every six hours about half of the nuclei decay. We say the half-life of technetium-99m is six hours. The half-life is the 1 time it takes for the activity to drop by half. 2 1 4 1 Question 8 0 0 6 12 18 24 1 What fraction of a radioactive material is left after: time (h) a one half-life? b  two half-lives? The decay curve for Technetium-99m.270
  • 18. P6: Radioactive materialsTime Hours since Number of Fraction of original injection half-lives sample remaining9.00 am 0 0 13.00 pm 6 1 ​  1 __ ​ 2 19.00 pm 12 2 ​ __ ​ 4 13.00 am 18 3 ​ __ ​ 8 19.00 am 24 4 ​ __ ​ 16   The radioactive decay of technetium-99m. 100The six-hour half-life makes it a useful medical tracer. It % of radon-220 activitylasts long enough for doctors to get some scans of the decay,but it has almost all gone in a few days. 50Different half-lives 25 12.5All radioactive materials show the same pattern but they can 0 0 1 2 3have different half-lives. The graph on the right shows the time (min)pattern of radioactive decay for radon. The decay curve for radon-220.There is no way of slowing down or speeding up the rate at Isotope Half-lifewhich radioactive materials decay. No chemical reaction ofphysical change makes any difference. Some decay slowly over Iridium-192 74 daysthousands of millions of years. Others decay in milliseconds – Strontium-81 22 minutesless than the blink of an eye. Uranium-235 710 million yearsThe shorter the half-life, the greater the activity for the sameamount of material. Of the four radioactive isotopes listed in Neon-17 0.1 secondsthe table on the right, neon-17 is the most active. Half-lives can be short or long. Question 2 Iodine-123 is used to investigate problems with the Summary box thyroid gland. It is a gamma emitter. DDHalf-life is the time a Explain why it is useful that iodine-123 gives out it takes for the activity of a gamma radiation. radioactive material b Iodine-123 has a half-life of 13 hours. Why would it be to drop by half. a problem if the half-life was: DDRadioactive materials i a lot shorter? have a wide range of ii a lot longer? half-lives. G: Half-life 271
  • 19. H Medical imaging and treatment Radioactive materials can cause cancer. But they can also be Find out about used to diagnose and cure many health problems. D different uses of radiation Medical imaging D types of radiation Jo has been feeling unusually tired for some time. Her doctors D benefits and risks decide to investigate whether an infection may have damaged of using radioactive her kidneys when she was younger. materials They plan to give her an injection of DMSA. This is a chemical D limiting radiation that is taken up by normal kidney cells. dose The DMSA has been labelled as radioactive. This means its molecules contain an atom of technetium-99m (Tc-99m), which is radioactive. The Tc-99m gives out its gamma radiation from within the kidneys. Gamma radiation is very penetrating, so nearly all of it escapes from Jo’s body and is picked up by a gamma camera. Jo’s scan shows that she has only a small area of damage. The doctors will take no further action. Glowing in the dark Jo was temporarily contaminated by radioactive technetium. For the next few hours, until her body got rid of the technetium, she was told to: this gamma scan shows • flush the toilet a few times after using it correctly functioning kidneys – the top two white areas. • wash her hands thoroughly • void close physical contact with friends and family. a Is it worth it? There was a small chance that some gamma radiation would damage Jo’s healthy cells. Before the treatment, her mum had to sign a consent form, and the doctors checked that Jo was not pregnant. Exposure to gamma Put mind at rest radiation GAMMA Can treat problem SCAN Jo’s mum weighed the risk against the benefit and felt the investigation was worth it. RISKS BENEFITS 272
  • 20. P6: Radioactive materialsJo’s mum said ‘We felt the risk was very small. It was worthit to find out what was wrong. Even with ordinary medicines,there can be risks. You have to weigh these things up. Nothingis completely safe.’Treatment for thyroid cancer thyroid glandAlf has thyroid cancer. First, he will have surgery to removethe tumour. Then he must have radiotherapy, to kill anycancer cells that may remain. The thyroid gland is located in the front of the neck, below the voice box.A hospital leaflet describes what will happen. Radioiodine treatment You will have to come in to hospital for a few days. You will stay in a single room. You will be given a capsule to swallow, which contains iodine-131. This form of iodine is radioactive. You cannot eat or drink anything else for a couple of hours. • The radioiodine is absorbed in your body. • Radioiodine naturally collects in your thyroid, because this gland uses iodine to make its hormone. Summary box • The radioiodine gives out beta radiation, which is DDRadioactive materials can be absorbed in the thyroid. used to diagnose • Any remaining cancer cells should be killed by the radiation. and treat medical problems. You will have to stay in your room and take some precautions DDThere are benefits for the safety of visitors and staff. You will remain in hospital and risks when using for a few days, until the amount of radioactivity in your body radioactive has fallen sufficiently. materials. Questions 1 Look at the precautions that Jo has to 3 What are the risks and the benefits to Jo take after the scan. Write a few sentences of having the treatment? explaining to Jo why she has to do each 4 Suggest how the risk to Alf’s family and of them. other patients is kept as low as possible. 2 It would be safe to stand next to Jo but 5 Explain why a half-life of eight days is not to kiss her. Use the words ‘irradiation’ more suitable than: and ‘contamination’ to explain why. a eight minutes b eight years H: Medical imaging and treatment 273
  • 21. I Nuclear power Nuclear fission Find out about Radioactive atoms have an unstable nucleus. Some nuclei can D energy from nuclear be made so unstable that they split in two. This process is fission called nuclear fission. D nuclear power smaller nucleus stations ENERGY neutron U-235 nucleus splitting the nucleus of an atom. When the nucleus breaks apart a small amount of the mass of the nucleus is converted to a huge amount of energy. So the products of nuclear fission have a lot of kinetic energy. Each fission reaction produces roughly a million times more energy than when a molecule changes during a chemical reaction. Nuclear weapons during the second World War there was a race to ‘split the atom’ and use the energy in a bomb. on 16 July 1945, in a desert in the usa, a group of scientists tested ‘the gadget’. some thought it would not work. others worried that it might destroy the atmosphere. at 5.29 a.m., it was detonated and filled the skies with light. the bomb vaporized the metal tower supporting it. all desert sand within a distance of 700 m was turned into glass. some of the scientists were worried about the power of the bomb and wanted the project stopped. a few weeks later, the devastating power of a the americans dropped two nuclear bombs on Japan. nuclear weapon. 274
  • 22. P6: Radioactive mateRialsGenerating electricityA nuclear power station uses a nuclear reactor. This is designed to release the energy of at a slow and steady rate. The fission takes place in the nuclear fuel. This makes them extremely hot.A fluid, called a coolant, is pumped through the reactor. The hot fuel rods heat the coolant to around 500 ˚C. It then flows through a heat exchanger in the boiler, turning water into steam. the reactor core is sealed andThe steam is used in the same way as in a coal- or gas-fired shielded. very little radiationpower station. One reason for building nuclear power stations gets out.is to reduce the need for fossil fuels.Nuclear weaponsCountries sometimes build nuclear reactors to make nuclear material for weapons. Nuclear weapons inspectors try to ensure that nuclear power stations are very secure, account for all their waste and are not operated in unstable countries. Questions 1 explain why these countries might decide to build, or not to build, nuclear power stations. a no reserves of gas or coal. b a neighbouring country that has nuclear weapons. c a small land area, and a large population. d a population worried about climate change. e a history of nuclear accidents. When the fuel rods are being 2 suggest how gamma radiation from a nuclear reactor is used they become more contained, so that living things are not irradiated. radioactive because of the waste products. 3 Write down two risks and two benefits of living in a country with nuclear power stations. Summary box D In nuclear fission a nucleus splits, releasing energy. The energy released is much greater than in a chemical reaction. I: nucleaR PoWeR 275
  • 23. J Nuclear waste Nuclear waste in the UK Find out about The Nuclear Decommissioning Agency (NDA) is responsible for D the UK’s nuclear cleaning up nuclear waste. Most of the radioactive waste comes waste from power stations. The rest comes from medical uses, industry D the half-life of and scientific research. In addition to this ‘everyday’ waste, radioactive when power stations are too old to be used anymore the waste materials radioactive materials must be taken away to be stored. The D possible methods of waste is called the UK’s ‘nuclear legacy’. disposal A long-term hazard Radioactive waste has very little effect on the UK’s average background radiation. But it is still hazardous. This is because of contamination. Imagine that some waste leaks into the water supply. This could be taken up by food, which you eat. The radioactive material is now in your stomach, where it can irradiate your internal organs. Some radioactive materials last for thousands of years. They must be kept safe and secure for all that time. high-level radioactive waste is Types of waste hot, so it is stored the nuclear industry deals with three underwater. types of nuclear waste. • High-level waste (hlW). this is ‘spent’ fuel rods. hlW gets hot because it is so radioactive. it has to be stored carefully but it doesn’t last long. and there isn’t very much of it. all the uK’s hlW is kept in a pool of water at sellafield. • Intermediate-level waste (ilW). this is less radioactive than hlW. But the amount of ilW is increasing, as hlW decays to become ilW. • Low-level waste (llW). Protective clothing and medical equipment can be slightly radioactive. it is packed in the control room at a nuclear waste storage drums and dumped in a landfill site plant. People monitor the waste continuously. that has been lined to prevent leaks. 276
  • 24. P6: Radioactive materialsType of waste Volume (m3) Radioactivity 100% remaining in high-level waste percentage of radioactivityLLW 196 000 weakILW 92 500 strong 50%HLW 1730 extremely strong The amount of nuclear waste in store (2007). The problem of what to do with it remains unsolved. 0 50 100 10000Sellafield time in years (note changing scale)Sellafield, in Cumbria, is the biggest nuclear site in High Level Waste decays quickly at first. When its activity falls, itthe UK. Thousands of people work there. Sellafield processes becomes Intermediate Levelnuclear waste and stores it ready for permanent disposal. Waste. ILW stays radioactive for thousands of years.Keeping risks low is very important at Sellafield. They haveplans to maintain production and safety if anything goes wrong.Intermediate-level waste is the biggest technical challenge, When will it be ‘safe’?because it is very long-lived. Currently it is chopped up, mixed We are exposed to somewith concrete, and stored in thousands of large stainless-steel radiation all the timecontainers. This is secure but not permanent. The long-term (background radiation).solution has to be secure and permanent. When the nuclear waste only emits very low levelsThe work of the NDA of radiation, similar to theManaging waste is very expensive. In 2010 the NDA spent background radiation,£28 billion. There have been a number of public consultations it poses little risk. Theabout what to do with the waste. At the time of writing these longer the half-life ofare still going on. The preferred plan at the moment is to store the radioactive material, the longer it will take toit until a safe site can be found to bury it. become ‘safe’. Questions 1 Explain why disposing of ILW needs to be both a secure and b permanent 2 What are the advantages and disadvantages of keeping all the waste together above ground rather than burying it in a deep shaft and sealing it? Summary box DDNuclear waste is 3 A small amount of nuclear fuel produces a lot of energy, radioactive and so in the 1950s scientists thought this would be a cheap must be safely way of generating electricity. Explain why the real cost is stored for thousands much greater than realised at the time. of years. J: Nuclear waste 277
  • 25. K Nuclear fusion In nuclear fusion the nuclei of two small atoms join together Find out about and energy is released. D nuclear fusion The diagram below shows one possible hydrogen fusion D the iter project reaction. Two hydrogen nuclei fuse to make a helium nucleus, and there is a neutron left over. left-over neutron Hydrogen Helium Fusion Hydrogen fusion of two hydrogen nuclei gives helium. The two hydrogen nuclei in the diagram have different numbers of neutrons, but you can tell they are both hydrogen because they have just one proton in the nucleus. Helium is formed. It has two protons. Helium is an unreactive gas. Positive charges repel It is difficult to get the two hydrogen nuclei close enough to fuse, because both nuclei have a positive electric charge. Similar charges repel. The hydrogen nuclei must have enough energy to overcome this force and collide, so that they can fuse. When the nuclei do fuse the new nucleus is more stable, and energy is released. The amount of energy released is very large. hydrogen is fused to helium in The quest for fusion power stations the sun. This is what scientists want to do: • fuse the hydrogen nuclei from water to give helium nuclei • use the energy released by this fusion reaction to generate electricity in power stations.278
  • 26. P6: Radioactive mateRialsThe advantages are:• the fuel is water, so there is plenty and it is cheap The H bomb• nuclear fusion does not produce as much radioactive waste hydrogen bombs, which as nuclear fission. fuse hydrogen, releaseOver the past 70 years there has been a lot of research. hundreds of times more energy than atomicScientists can give hydrogen nuclei enough energy to (fission) bombs. they areovercome the repulsive force. The problem is controlling the triggered using an atomicreaction and keeping it going. bomb to compress theWhen hydrogen is heated to a very high temperature, the hydrogen so that it fuses.atoms lose their electrons and form a cloud of charged particles called a plasma. This is kept from touching the sides of the container by using magnetic fields. The JET project in the UK has researched fusion for many years. So far no reactor has produced more energy than it used.The ITER projectThis is a joint project between China, the European Atomic Energy Community, India, Japan, Korea, Russia and the USA. ITER means ‘the way’ in Latin. Fusion research is very expensive so these countries have joined together to build a research reactor in France. Construction has begun. It will take 10 years to build, and be used for research for 20 years. ITER will investigate how plasmas behave during the hydrogen fusion reaction at 150 million ЊC. One day they hope the planned iteR fusionto build a nuclear fusion power station. reactor. fusion will take place in the doughnut-shaped hole. Questions 1 When two hydrogen nuclei fuse what element is formed? 2 a What is the electric charge on a hydrogen nucleus? b explain whether two hydrogen nuclei attract or repel. 3 What are the advantages of countries working together on the iteR project? Summary box D Nuclear fusion 4 iteR is very expensive. Write a letter to persuade the releases energy. government eitheR: D Hydrogen nuclei a to stay part of iteR or fuse to form helium b to leave iteR to save money. nuclei. K: nucleaR fusion 279
  • 27. ScienceExplanationsOur understanding of radioactivity and the structure of the atom has enabledmany applications, such as nuclear power stations and cancer treatment, to bedeveloped. Knowledge of the way ionising radiation behaves is essential forworking safely and making good risk assessments. ow: You should kn heliu m why some materials are radioactive and emit ionising radiation all the time hydrog how ionising radiation can damage living cells en that atoms have a nucleus made of protons and neutrons and is surrounded by electrons plutonium about the alpha scattering experiment and how it showed that the atom has a small, massive, positively charged nucleus that there are alpha and beta particles and gamma radiation uranium about the different penetration properties of alpha, beta, and gamma radiations  that there is background radiation all around us, mostly from natural sources what radiation dose measures, and what factors affect it foo d the difference between contamination and irradiation how to interpret data on risk related to radiation dose surg ical in struments that radioactive materials randomly emit ionising radiation all the time and that the rate of decay cannot be changed by physical or chemical changes ti o n i r ra d i a that the activity of a radioactive source decreases over time io n what is meant by the half-life of a radioactive isotope m i n at that radioactive sources have a wide range of half-life values nta co about how the half-life of a radioactive source affects the time it takes to become safe about uses of ionising radiation from radioactive materials and the people who work with them that nuclear fuels release energy when the nucleus changes during nuclear fission about the three categories of radioactive waste, and the different methods of disposal nuc lear that hydrogen nuclei can fuse together to form helium if they are brought was te close enough together and this releases energy that the energy released in a nuclear reaction is much greater than that released in a chemical reaction such as burning a similar mass of fuel.280
  • 28. P6: Radioactive mateRials f u sio n g tterin n sio ci n g r i s k fis sca cle r a d i o a c ti ironme l impact rti ve pa nuclei de re d u ca ha e y li f a lp lf- n nta atio ha radi n mea a om particles and gamm env e re a d i n g g r a p h s rang e at of th benefits ata d risk structure ing s us ing n latio ss ts calcu sse s a co beta k? who takes ris is k ive? and m at h s s k i l l s r are they radioact ha b e n e fi alp tio n t ? ra f its ce et ne who be ien lth n f sc pe hea so ce en equ cons why decisions s tre official regulation as a tr RADIOACTIVE ati ca ng nc MATERIALS ace er ste r rilis qu atio es n on ti nn s tha ely us ca saf ot t sc d o utco m es es da an ienc m ma sw e er the ge t o living cells using and handling tion rs a n background radia dose in sieverts to fac ionising radiation ite R pr oject n io fu om t la sio eus re use y fr e a r p o we r s t at i o n cor nn u cl fi s si o n ucl erg ca en en th P6: Radioac tive mateRials 281
  • 29. Ideas about Science In addition to developing an understanding of • identify risks and benefits to individuals and radioactive materials, it is important to appreciate groups. Many medical treatments make use of the risks involved and how we make decisions radioactive isotopes. The risk and the benefit to about using science and technology. When the patient must be weighed up. considering risk, you should be able to: • take into account, in making decisions, who • explain that nothing is completely safe. benefits and who takes the risks, for example, Everything we do has a certain risk. when deciding whether to build a nuclear Background radiation is all around us, so there power station. is always a risk of our cells being harmed by • suggest benefits of activities known to have ionising radiation. But if the dose is low the risk, for example, a scan that involves injecting risk is very small. a radioactive tracer into the body. • list some of the uses of radioactive materials • suggest reasons why people are willing (or and the risks arising from them, both to people reluctant) to take a risk. For example, people working with radioactive sources and to the who are ill may choose to have treatment in the environment. hope that they will be cured. Some people may • describe some of the ways that we reduce refuse treatment if doctors say they must have these risks. it, as they prefer to choose for themselves. • use data to compare and discuss different risks. Compare the risks of living in a high-radon In making decisions about science and technology, area with risks of other activities, for example, you should be able to: smoking tobacco. • identify the groups affected by a decision, and • discuss decisions involving risk. To decide the main benefits and costs for each group, for whether to build a type of nuclear power example, when deciding on a location for a station you would need to take account of the waste-disposal site. chance of contaminating the environment and • explain that different decisions may be made how serious that would be. depending on social and economic factors. Nuclear power stations are built in remote areas where they will affect fewer people. Countries with no other resources for generating electricity may choose to build nuclear power stations. • explain that there is official regulation of some areas of research and application of knowledge. Countries that have nuclear power stations keep account of all the radioactive waste, as this could be processed to produce nuclear weapons. • distinguish questions that can be answered using a scientific approach from those that cannot, for example, ‘Shall we build a nuclear power station at this site?’ If there is no scientific reason why not, the final decision still depends on what society wants to do.282
  • 30. P6: Radioactive mateRials Review Questions1 Copy and complete the sentences about 5 The table shows some of the radioactive radioactivity. Use key words from the module. isotopes that are used in a range of applications. _____________ radiation is produced by radioactive _________________ . The radiation Isotope Radiation Half-life is produced when an _______________ nucleus emitted __________________ . The three types of americium-241 alpha 430 years radiation produced are: _____________ particles, __________________ particles, and carbon-14 beta 5700 years ________________, which is electromagnetic cobalt-60 gamma 5 years radiation. iodine-123 gamma 13 hours iodine-131 beta 8 days2 Rutherford had to develop a new model of the atom to explain the results of the scattering strontium-90 beta 29 years experiment. uranium-235 alpha 700 million a How did he explain the fact that a few years alpha particles were scattered back For each application listed below choose the towards the source? isotope you think most suitable and justify your b Most alpha particles passed straight answer, referring to both the half-life and the through the foil. How did Rutherford radiation emitted. explain this? a calculating the age of rocks3 An isotope has a half-life of 74 days. Its b dating an ancient leather belt activity is measured at 10 000 decays per c monitoring the thickness of paper in a factory second. It emits alpha radiation. d monitoring uptake of iodine by the thyroid a What does a half-life of 74 days mean? e detecting smoke b Why could the isotope not be used to work f sterilising medical equipment out the age of rocks? 6 Nuclear power stations use radioactive 4 What is the difference between nuclear materials to generate electricity. The waste fission and nuclear fusion? from this process is radioactive. Explain how the three different categories of nuclear waste are treated. 7 Describe four sources of background radiation and explain whether each one is natural or man made. P6: Radioac tive mateRials 283
  • 31. Glossary abundant  Abundance measures how common an element is. Silicon is balanced equation  An equation showing the formulae of the reactants abundant in the lithosphere. Nitrogen is abundant in the atmosphere. and products. The equation is balanced when there is the same number of each kind of atom on both sides of the equation. acceleration  The rate of change of an object’s velocity, that is, its change of velocity per second. In situations where the direction of base pairing  The bases in a DNA molecule (A, C, G, T) always bond motion is not important, the change of speed per second tells you the in the same way. A and T always bond together. C and G always acceleration. bond together. acid  A compound that dissolves in water to give a solution with a pH behaviour  Everything an organism does; its response to all the stimuli lower than 7. Acid solutions change the colour of indicators, form around it. salts when they neutralize alkalis, react with carbonates to form beta blockers  Drugs that block the receptor sites for the hormone carbon dioxide, and give off hydrogen when they react with a metal. adrenaline. They inhibit the normal effects of adrenaline on the body. An acid is a compound that contains hydrogen in its formula and beta radiation  One of several types of ionising radiation, produced by produces hydrogen ions when it dissolves in water. the nucleus of an atom in radioactive decay. More penetrating than action at a distance  An interaction between two objects that are not in alpha radiation but less penetrating than gamma radiation. A high- contact, where each exerts a force on the other. Examples include two speed electron. magnets, two electric charges, or two masses (for example, the Earth bioethanol  Ethanol fuel produced by yeast fermentation of plant and the Moon) materials, such as cane sugar and sugar beet. active site  The part of an enzyme that the reacting molecules fit into. biogas  Methane gas produced by the anaerobic digestion of organic active transport  Molecules are moved in or out of a cell using energy. material, such as farm animal manure. This process is used when transport needs to be faster than diffusion, bleach  A chemical that can destroy unwanted colours. Bleaches also kill and when molecules are being moved from a region where they are at bacteria. A common bleach is a solution of chlorine in sodium hydroxide. low concentration to where they are at high concentration. bulk chemicals  Chemicals made by industry on a scale of thousands or activity  The rate at which nuclei in a sample of radioactive material millions of tonnes per year. Examples are sulfuric acid, nitric acid, decay and give out alpha, beta, or gamma radiation. sodium hydroxide, ethanol, and ethanoic acid. actual yield  The mass of the required chemical obtained after burette  A graduated tube with taps or valves used to measure the separating and purifying the product of a chemical reaction. volume of liquids or solutions during quantitative investigations such aerobic respiration  Respiration that uses oxygen. as titrations. air resistance  The force exerted on an object by the air, when it moves carbohydrate  A natural chemical made of carbon, hydrogen, and through it. Its direction is opposite to the direction in which the object oxygen. An example is glucose C6H12O6. Carbohydrates include is moving. sugars, starch, and cellulose. alkali  A compound that dissolves in water to give a solution with a pH 2– carbonate  A compound that contains carbonate ions, CO3 . An example higher than 7. An alkali can be neutralized by an acid to form a salt. is calcium carbonate, CaCO3. Solutions of alkalis contain hydroxide ions. cartilage  Tough, flexible tissue found at the end of bones and in joints. alkali metal  An element in Group 1 of the periodic table. Alkali metals It protects the end of bones from rubbing together and becoming react with water to form alkaline solutions of the metal hydroxide. damaged. alloy  A mixture of metals. Alloys are often more useful than pure metals. catalyst  A chemical that starts or speeds up a chemical reaction but is alpha radiation  The least penetrating type of ionising radiation, not used up in the process. produced by the nucleus of an atom in radioactive decay. A high-speed cell  The basic structural and functional unit of all living things. helium nucleus. cell membrane  Thin layer surrounding the cytoplasm of a cell. It alternating current (a.c.)  An electric current that reverses direction restricts the passage of substances into and out of the cell. many times a second. cell wall  Rigid outer layer of plant cells and bacteria. Alzheimer’s disease  A form of senile dementia caused by irreversible cellulose  The chemical that makes up most of the fibre in food. The degeneration of the brain. human body cannot digest cellulose. amino acids  The small molecules that are joined in long chains to make central nervous system  In mammals the brain and spinal cord. proteins. All the proteins in living things are made from 20 different amino acids joined in different orders. cerebral cortex  The highly folded outer region of the brain, concerned with conscious behaviour. ammeter  A meter that measures the size of an electric current in a circuit. chain reaction  A process in which the products of one nuclear reaction ampere (amp)  The unit of electric current. cause further nuclear reactions to happen, so that more and more anaerobic respiration  Respiration that does not use oxygen. reactions occur and more and more product is formed. Depending on antibodies  A group of proteins made by white blood cells to fight how this process is controlled, it can be used in nuclear weapons or dangerous microorganisms. A different antibody is needed to fight each the nuclear reactors in power stations. different type of microorganism. Antibodies bind to the surface of the charged  Carrying an electric charge. Some objects (such as electrons microorganism, which triggers other white blood cells to digest them. and protons) are permanently charged. A plastic object can be charged atmosphere  The layer of gases that surrounds the Earth. by rubbing it. This transfers electrons to or from it. attract  Pull towards. chemical change/reaction  A change that forms a new chemical. attractive forces (between molecules)  Forces that try to pull chemical equation  A summary of a chemical reaction showing the molecules together. Attractions between molecules are weak. reactants and products with their physical states (see balanced Molecular chemicals have low melting points and boiling points chemical equation). because the molecules are easy to separate. chemical industry  The industry that converts raw materials such as auxin  A plant hormone that affects plant growth and development. For crude oil, natural gas, and minerals into useful products such as example, auxin stimulates growth of roots in cuttings. pharmaceuticals, fertilisers, paints, and dyes. average speed  The distance moved by an object divided by the time chemical properties  A chemical property describes how an element or taken for this to happen. compound interacts with other chemicals, for example, the reactivity of a metal with water. axon  A long, thin extension of the cytoplasm of a neuron. The axon carries electrical impulses very quickly. chemical species  The different chemical forms that an element can take, for example, chlorine has three chemical species: atom, background radiation  The low-level radiation, mostly from natural molecule, and ion. Each of these forms has distinct properties. sources, that everyone is exposed to all the time, everywhere. chlorophyll  A green pigment found in chloroplasts. Chlorophyll absorbs bacterium (plural bacteria)  One type of single-celled microorganism. energy from sunlight for photosynthesis. They do not have a nucleus. Some bacteria may cause disease.284
  • 32. chloroplast  An organelle found in some plant cells where distance–time graph  A useful way of summarising the motion of an photosynthesis takes place. object by showing how far it has moved from its starting point at everychromosome  Long, thin, threadlike structures in the nucleus of a cell instant during its journey. made from a molecule of DNA. Chromosomes carry the genes. distance–time graph  A graph showing the distance an object movesclone  A new cell or individual made by asexual reproduction. A clone along its path at each moment during its journey. has the same genes as its parent. double helix  The shape of the DNA molecule, with two strands twistedcollision theory  The theory that reactions happen when molecules together in a spiral. collide. The theory helps to explain the factors that affect the rates of driving force  The force pushing something forward, for example, a chemical change. Not all collisions between molecules lead to reaction. bicycle.commutator  An device for changing the direction of the electric current Ecstasy  A recreational drug that increases the concentration of through the coil of a motor every half turn. It consists of a ring serotonin at the synapses in the brain, giving pleasurable feelings. divided into two halves (a split ring) with two contacts (brushes) Long-term effects may include destruction of the synapses. touching the two halves. effector  The part of a control system that brings about a change to theconcentrated solution  The concentration of a solution depends on how system. much dissolved chemical (solute) there is compared with the solvent. electric charge  A fundamental property of matter. Electrons and A concentrated solution contains a high level of solute to solvent. protons are charged particles. Objects become charged when electronsconcentration  The quantity of a chemical dissolved in a stated volume are transferred to or from them, for example, by rubbing. of solution. Concentrations can be measured in grams per litre. electric circuit  A closed loop of conductors connected between theconditioned reflex  A reflex where the response is associated with a positive and negative terminals of a battery or power supply. secondary stimulus, for example, a dog salivates when it hears a bell electric current  A flow of charges around an electric circuit. because it has associated the bell with food. electric field  A region where an electric charge experiences a force.conditioning  Reinforcement of behaviour associated with conditioned There is an electric field around any electric charge. reflexes. electrode  A conductor made of a metal or graphite through which aconscious  To have awareness of surroundings and sensations. current enters or leaves a chemical during electrolysis. Electrons flowconsciousness  The part of the human brain concerned with thought into the negative electrode (cathode) and out of the positive electrode and decision making. (anode).conservation of energy  The fundamental idea that the total amount of electrolysis  Splitting up a chemical into its elements by passing an energy in the universe is constant, and never increases or decreases. electric current through it. So if something loses energy, one or more other things must have electrolyte  A chemical that can be split up by an electric current when gained the same amount of energy. molten or in solution is the electrolyte. Ionic compounds arecontamination (radioactive)  Having a radioactive material inside the electrolytes. body, or having it on the skin or clothes. electromagnetic induction  The name of the process in which acontrol rod  In a nuclear reactor, rods made of a special material that potential difference (and hence often an electric current) is generated absorbs neutrons are raised and lowered to control the rate of fission in a wire, when it is in a changing magnetic field. reactions. electron  A tiny, negatively charged particle, which is part of an atom.coolant  In a nuclear reactor, the liquid or gas that circulates through the Electrons are found outside the nucleus. Electrons have negligible core and transfers heat to the boiler. mass and one unit of charge.corrosive  A corrosive chemical may destroy living tissue on contact. electron arrangement  The number and arrangement of electrons in ancounter-force  A force in the opposite direction to something’s motion. atom of an element.covalent bonding  Strong attractive forces that hold atoms together in electrostatic attraction  The force of attraction between objects with molecules. Covalent bonds form between atoms of non-metallic elements. opposite electric charges.crust (of the Earth)  The outer layer of the lithosphere. embryonic stem cell  Unspecialised cell in the very early embryo that can divide to form any type of cell, or even a whole new individual. Incrystalline  A material with molecules, atoms, or ions lined up in a human embryos the cells are identical and unspecialised up to the regular way as in a crystal. eight-cell stage.cutting  A shoot or leaf taken from a plant, to be grown into a new plant. end point  The point during a titration at which the reaction is justcytoplasm  Gel enclosed by the cell membrane that contains the cell complete. For example, in an acid–alkali titration, the end point is organelles such as mitochondria. reached when the indicator changes colour. This happens whendecommissioning  Taking a power station out of service at the end of its exactly the right amount of acid has been added to react with all the lifetime, dismantling it, and disposing of the waste safely. alkali present at the start.denatured  A change in the usual nature of something. When enzymes endothermic  An endothermic process takes in energy from its are denatured by heat, their structure, including the shape of the surroundings. active site, is altered. energy level  The electrons in an atom have different energies and aredevelopment  How an organism changes as it grows and matures. As a arranged at distinct energy levels. zygote develops, it forms more and more cells. These are organised energy-level diagram  A diagram to show the difference in energy into different tissues and organs. between the reactants and the products of a reaction.diamond  A gemstone. A form of carbon. It has a giant covalent structure enzyme  A protein that catalyses (speeds up) chemical reactions in living and is very hard. things.diatomic  A molecule with two atoms, for example, N2, O2, and Cl2 ethanol  Waste product from anaerobic respiration in plants and yeast.diffusion  Movement of molecules from a region of high concentration to exothermic  An exothermic process gives out energy to its surroundings. a region of lower concentration. extraction (of metals)  The process of obtaining a metal from a mineraldilute  The concentration of a solution depends on how much dissolved by chemical reduction or electrolysis. It is often necessary to chemical (solute) there is compared with the solvent. A dilute solution concentrate the ore before extracting the metal. contains a low level of solute to solvent. fatty sheath  Fat wrapped around the outside of an axon to insulatedirect current (d.c.)  An electric current that stays in the same neurons from each other. direction. feral  Untamed, wild.displacement reaction  A more reactive halogen will displace a less fermentation   Chemical reactions in living organisms that release reactive halogen, for example, chlorine will displace bromide ions to energy from organic chemicals, such as yeast producing alcohol from form bromine and chloride ions. the sugar in grapes.dissolve  Some chemicals dissolve in liquids (solvents). Salt and sugar, fermenter  A large vessel in which microorganisms are grown to make a for example, dissolve in water. useful product.distance  The length of the path along which an object moves. 285
  • 33. fetus   A developing human embryo is referred to as a fetus once it hormone  A chemical messenger secreted by specialised cells in animals reaches eight weeks after fertilization. A fetus already has all the main and plants. Hormones bring about changes in cells or tissues in organs that it will have at birth. different parts of the animal or plant. fine chemicals  Chemicals made by industry in smaller quantities than hydrogen ion  A hydrogen atom that has lost one electron. The symbol bulk chemicals. Fine chemicals are used in products such as food for a hydrogen ion is H+. Acids produce aqueous hydrogen ions, additives, medicines, and pesticides. H+(aq), when dissolved in water. flame colour  A colour produced when a chemical is held in a flame. hydrosphere  All the water on Earth. This includes oceans, lakes, rivers, Some elements and their compounds give characteristic colours. underground reservoirs, and rainwater. Sodium and sodium compounds, for example, give bright yellow hydroxide ion  A negative ion, OH–. Alkalis give aqueous hydroxide ions flames. when they dissolve in water. food chain  In the food industry this covers all the stages from where in parallel  A way of connecting electric components that makes a food grows, through harvesting, processing, preservation, and cooking branch (or branches) in the circuit so that charges can flow around to being eaten. more than one loop. force  A push or a pull experienced by an object when it interacts with in series  A way of connecting electric components so that they are all in another. A force is needed to change the motion of an object. a single loop. The charges pass through them all in turn. formulae (chemical)  A way of describing a chemical that uses symbols indicator  A chemical that shows whether a solution is acidic or alkaline. for atoms. A formula gives information about the numbers of different For example, litmus turns blue in alkalis and red in acids. Universal types of atom in the chemical. The formula of sulfuric acid, for indicator has a range of colours that show the pH of a solution. example, is H2SO4. innate  Inborn, inherited from parents via genes. friction  The force exerted on an object due to the interaction between it and another object that it is sliding over. It is caused by the roughness insoluble  Does not form a solution (dissolve) in water or other solutes. of both surfaces at a microscopic level. instantaneous speed  The speed of an object at a particular instant. In fuel rod  A container for nuclear fuel, which enables fuel to be inserted practice, its average speed over a very short time interval. into, and removed from, a nuclear reactor while it is operating. interaction  What happens when two objects collide, or influence each gametes  The sex cells that fuse to form a zygote. In humans, the male other at a distance. When two objects interact, each experiences a gamete is the sperm and the female gamete is the egg. force. gamma radiation (gamma rays)  The most penetrating type of ionising interaction pair  Two forces that arise from the same interaction. They are radiation, produced by the nucleus of an atom in radioactive decay. equal in size and opposite in direction, and each acts on a different object. The most energetic part of the electromagnetic spectrum. intermediate-level waste  A category of nuclear waste that is generally gas exchange  The exchange of oxygen and carbon dioxide that takes short-lived but requires some shielding to protect living organisms, for place in the lungs. example contaminated materials that result from decommissioning a nuclear reactor. gene  A section of DNA giving the instructions for a cell about how to make one kind of protein. involuntary  An automatic response made by the body without conscious thought. gene switching  Genes in the nucleus of a cell switch off and are inactive when a cell becomes specialised. Only genes that the cell needs to ion  An electrically charged atom or group of atoms. carry out its particular job stay active. ionic bonding  Very strong attractive forces that hold the ions together generator  A device that uses motion to generate electricity. It consists of in an ionic compound. The forces come from the attraction between a coil that rotates in a magnetic field. This produces a potential positively and negatively charged ions. difference across the ends of the coil, which can then be used to ionic compounds  Compounds formed by the combination of a metal provide an electric current. and a non-metal. They contain positively charged metal ions and genetic  Factors that are affected by an organism’s genes. negatively charged non-metal ions. genetic variation  Differences between individuals caused by differences ionic equation  An ionic equation describes a chemical change by in their genes. Gametes show genetic variation – they all have showing only the reacting ions in solution. different genes. ionising  Able to remove electrons from atoms, producing ions. giant covalent structure  A giant, three-dimensional arrangement of ionising radiation  Radiation with photons of sufficient energy to atoms that are held together by covalent bonds. Silicon dioxide and remove electrons from atoms in its path. Ionising radiation, such as diamond have giant covalent structures. ultraviolet, X-rays, and gamma rays, can damage living cells. giant ionic lattice  The structure of solid ionic compounds. There are no irradiation  Being exposed to radiation from an external source. individual molecules, but millions of oppositely charged ions packed isotope  Atoms of the same element that have different mass numbers closely together in a regular, three-dimensional arrangement. because they have difference numbers of neutrons in the nucleus. glands  Parts of the body that make enzymes, hormones, and other kinetic energy  The energy that something has owing to its motion. secretions in the body, for example, sweat glands. lactic acid  Waste product from anaerobic respiration in animals. glucose  Sugar produced during photosynthesis. learn  To gain new knowledge or skills. graphite  A form of carbon. It has a giant covalent structure. It is unusual for a non-metal in that it conducts electricity. life cycle  The stages an organism goes through as it matures, develops, and reproduces. gravitational potential energy  The energy stored when an object is raised to a higher point in the Earth’s gravitational field. light intensity  The amount of light reaching a given area. group  Each column in the periodic table is a group of similar elements. light meter  Device for measuring light intensity. habitat  The place where an organism lives. light-dependent resistor (LDR)  An electric circuit component whose resistance varies depending on the brightness of light falling on it. haemoglobin  The protein molecule in red blood cells. Haemoglobin binds to oxygen and carries it around the body. It also gives blood its limiting factor  The factor that prevents the rate of photosynthesis from red colour. increasing at a particular time. This may be light intensity, temperature, carbon dioxide concentration, or water availability. half-life  The time taken for the amount of a radioactive element in a sample to fall to half its original value. line spectrum  A spectrum made up of a series of lines. Each element has its own characteristic line spectrum. halogens  The family name of the Group 7 elements. lithosphere  The rigid outer layer of the Earth, made up of the crust and harmful  A harmful chemical is one that may cause damage to health if the part of mantle just below it. swallowed, breathed in, or absorbed through the skin. lock-and-key model  In chemical reactions catalysed by enzymes, high-level waste  A category of nuclear waste that is highly radioactive molecules taking part in the reaction fit exactly into the enzyme’s and hot. Produced in nuclear reactors and nuclear-weapons active site. The active site will not fit other molecules – it is specific. processing. This is like a key fitting into a lock.286
  • 34. long-term memory  The part of the memory that stores information for neutralization reaction  A reaction in which an acid reacts with an a long period, or permanently. alkali to form a salt. During neutralization reactions, the hydrogenlow-level waste  A category of nuclear waste that contains small ions in the acid solution react with hydroxide ions in the alkaline amounts of short-lived radioactivity, for example, paper, rags, tools, solution to make water molecules. clothing, and filters from hospitals and industry. neutrons  An uncharged particle found in the nucleus of atoms. Themagnetic field  The region around a magnet, or a wire carrying an relative mass of a neutron is 1. electric current, in which magnetic effects can be detected. For newborn reflexes  Reflexes to particular stimuli that usually occur only example, another small magnet in this region will experience a force for a short time in newborn babies. and may tend to move. nitrate ions  An ion is an electrically charged atom or group of atoms.mantle  The layer of rock between the crust and the outer core of the The nitrate ion has a negative charge, NO3–. Earth. It is approximately 2900 km thick. non-ionising radiation  Radiation with photons that do not have enoughmeiosis  Cell division that halves the number of chromosomes to energy to ionize molecules. produce gametes. The four new cells are genetically different from nuclear fission  The process in which a nucleus of uranium-235 breaks each other and from the parent cell. apart, releasing energy, when it absorbs a neutron.memory  The storage and retrieval of information by the brain. nuclear fuel  In a nuclear reactor, each uranium atom in a fuel rodmeristem cells  Unspecialised cells in plants that can develop into any undergoes fission and releases energy when hit by a neutron. kind of specialised cell. nuclear fusion  The process in which two small nuclei combine to form ametal  Elements on the left side of the periodic table. Metals have larger one, releasing energy. An example is hydrogen combining to characteristic properties: they are shiny when polished and they form helium. This happens in stars, including the Sun. conduct electricity. Some metals react with acids to give salts and nucleus (atom)  The tiny central part of an atom (made up of protons hydrogen. Metals are present as positive ions in salts. and neutrons). Most of the mass of an atom is concentrated in itsmetal hydroxide  A compound consisting of metal positive ions and nucleus. hydroxide ions. Examples are sodium hydroxide, NaOH, and nucleus (cell)  Organelle that contains the chromosomes cells of plants, magnesium hydroxide, Mg(OH)2. animals, fungi, and some microorganisms.metal oxide  A compound of a metal with oxygen. ohm  The unit of electrical resistance. Symbol Ω.metallic bonding  Very strong attractive forces that hold metal atoms Ohm’s law  The result that the current, I, through a resistor, R, is together in a solid metal. The metal atoms lose their outer electrons proportional to the voltage, V, across the resistor, provided its and form positive ions. The electrons drift freely around the lattice of temperature remains the same. Ohm’s law does not apply to all positive metal ions and hold the ions together. conductors.mineral  A naturally occurring element or compound in the Earth’s optimum temperature  The temperature at which enzymes work fastest. lithosphere. ore  A natural mineral that contains enough valuable minerals to make itmitochondrion (plural mitochondria)  An organelle in animal and profitable to mine. plant cells where respiration takes place. organelles  The specialised parts of a cell, such as the nucleus andmitosis  Cell division that makes two new cells identical to each other mitochondria. Chloroplasts are organelles that occur only in plant cells. and to the parent cell. organs  Parts of a plant or animal made up of different tissues.models of memory  Explanations for how memory is structured in the brain. osmosis  The diffusion of water across a partially permeable membrane.molecular models  Models to show the arrangement of atoms in oxidation  A reaction that adds oxygen to a chemical. molecules, and the bonds between the atoms. oxide  A compound of an element with oxygen.molecule  A group of atoms joined together. Most non-metals consist of pancreas  An organ in the body that produces some hormones and molecules. Most compounds of non-metals with other non-metals are digestive enzymes. The hormone insulin is made here. also molecular. partially permeable membrane  A membrane that acts as a barrier tomolten  A chemical in the liquid state. A chemical is molten when the some molecules but allows others to diffuse through freely. temperature is above is melting point but below its boiling point. pathway  A series of connected neurones that allow nerve impulses tomomentum (plural momenta)  A property of any moving object. Equal travel along a particular route very quickly. to mass multiplied by velocity. percentage yield  A measure of the efficiency of a chemical synthesis.motor  A device that uses an electric current to produce continuous period  In the context of chemistry, a row in the periodic table. motion. periodic  In chemistry, a repeating pattern in the properties of elements.motor neuron  A neuron that carries nerve impulses from the brain or In the periodic table one pattern is that each period starts with metals spinal cord to an effector. on the left and ends with non-metals on the right.mRNA  Messenger RNA, a chemical involved in making proteins in cells. peripheral nervous system  The network of nerves connecting the The mRNA molecule is similar to DNA but single stranded. It carries central nervous system to the rest of the body. the genetic code from the DNA molecule out of the nucleus into the cytoplasm. pH scale  A number scale that shows the acidity or alkalinity of a solution in water.multi-store model  One explanation for how the human memory works. phloem  A plant tissue that transports sugar throughout a plant.muscles  Muscles move parts of the skeleton for movement. There is also muscle tissue in other parts of the body, for example, in the walls of photons  Tiny ‘packets’ of electromagnetic radiation. All electromagnetic arteries. waves are emitted and absorbed as photons. The energy of a photon is proportional to the frequency of the radiation.negative  A label used to name one type of charge or one terminal of a battery. It is the opposite of positive. photosynthesis  The process in green plants that uses energy from sunlight to convert carbon dioxide and water into the sugar glucose.negative ion  An ion that has a negative charge (an anion). phototropism  The bending of growing plant shoots towards the light.nerve cell  A cell in the nervous system that transmits electrical signals to allow communication within the body. physical properties  Properties of elements and compounds such as melting point, density, and electrical conductivity. These arenerve impulses  Electrical signals carried by neurons (nerve cells). properties that do not involve one chemical turning into another.nervous system  Tissues and organs that control the body’s responses to pilot plant  A small-scale chemical processing facility. A pilot plant is stimuli. In a mammal it is made up of the central nervous system and used to test processes before scaling up to full-scale production. peripheral nervous system. plant  A chemical plant is an industrial facility used to manufactureneuron  Nerve cell. chemicals.neuroscientist  A scientist who studies how the brain and nerves plasma  A collection of electrons and nuclei that can be formed when a function. gas has so much energy that its atoms are fully ionised. 287
  • 35. polymer  A material made up of very long molecules. The molecules are red blood cells  Blood cells containing haemoglobin, which binds to long chains of smaller molecules. oxygen so that it can be carried around the body by the bloodstream. positive  A label used to name one type of charge, or one terminal of a reducing agent  A chemical that removes oxygen from another battery. It is the opposite of negative. chemical. For example, carbon acts as a reducing agent when it positive ion  Ions that have a positive charge (cations). removes oxygen from a metal oxide. The carbon is oxidized to carbon monoxide during this process. potential difference (p.d.)  The difference in potential energy (for each unit of charge flowing) between any two points in an electric circuit. reduction  A reaction that removes oxygen from a chemical. power  In an electric circuit, the rate at which work is done by the battery reflex arc  A neuron pathway that brings about a reflex response. or power supply on the components in a circuit. Power is equal to A reflex arc involves a sensory neuron, connecting neurons in the current × voltage. brain or spinal cord, and a motor neuron. precipitate  An insoluble solid formed on mixing two solutions. Silver relative atomic mass  The mass of an atom of an element compared to bromide forms as a precipitate on mixing solutions of silver nitrate the mass of an atom of carbon. The relative atomic mass of carbon is and potassium bromide. defined as 12. proportional  Two variables are proportional if there is a constant ratio relative formula mass  The combined relative atomic masses of all the between them. atoms in a formula. To find the relative formula mass of a chemical, you just add up the relative atomic masses of the atoms in the protein  Chemicals in living things that are polymers made by joining formula. together amino acids. relay neuron  A neuron that carries the impulses from the sensory proton  Tiny particle present in the nuclei of atoms. Protons are neuron to the motor neuron. positively charged (+1). repel  Push apart. proton number  The number of protons in the nucleus of an atom (also called the atomic number). In an uncharged atom this also gives the repetition  Act of repeating. number of electrons. repetition of information  Saying or writing the same thing several Prozac  A brand name for an antidepressant drug. It increases the times. concentration of serotonin at the synapses in the brain. resistance  The resistance of a component in an electric circuit indicates pupil reflex  The reaction of the muscles in the pupil to light. The pupil how easy or difficult it is to move charges through it. contracts in bright light and relaxes in dim light. respiration  A series of chemical reactions in cells that release energy quadrat  A square grid of a known area that is used to survey plants in a for the cell to use. location. Quadrats come in different sizes up to 1 m2. The size of response  Action or behaviour that is caused by a stimulus. quadrat that is chosen depends on the size of the plants and also the resultant force  The sum, taking their directions into account, of all the area that needs to be surveyed. forces acting on an object. radiation  A flow of information and energy from a source. Light and retina  Light-sensitive layer at the back of the eye. The retina detects infrared are examples. Radiation spreads out from its source, and may light by converting light into nerve impulses. be absorbed or reflected by objects in its path. It may also go (be transmitted) through them. retrieval of information  Collecting information from a particular source. radiation dose  A measure, in millisieverts, of the possible harm done to your body, which takes into account both the amount and type of ribosomes  Organelles in cells. Amino acids are joined together to form radiation you are exposed to. proteins in the ribosomes. radioactive  Used to describe a material, atom, or element that produces risk  The probability of an outcome that is seen as undesirable, alpha, beta, or gamma radiation. associated with some behaviour or process. radioactive dating  Estimating the age of an object such as a rock by risk assessment  A check on the hazards involved in a scientific measuring its radioactivity. Activity falls with time, in a way that is procedure. A full assessment includes the steps to be taken to avoid or well understood. reduce the risks from the hazards identified. radioactive decay  The spontaneous change in an unstable element, rock  A naturally occurring solid, made up of one or more minerals. giving out alpha, beta, or gamma radiation. Alpha and beta emission root hair cell  Microscopic cell that increases the surface area for result in a new element. absorption of minerals and water by plant roots. radiotherapy  Using radiation to treat a patient. rooting powder  A product used in gardening containing plant random  Of no predictable pattern. hormones. Rooting powder encourages a cutting to form roots. rate of photosynthesis  Rate at which green plants convert carbon salt  An ionic compound formed when an acid neutralizes an alkali or dioxide and water to glucose in the presence of light. when a metal reacts with a non-metal. rate of reaction  A measure of how quickly a reaction happens. Rates sample  Small part of something that is likely to represent the whole. can be measured by following the disappearance of a reactant or the scale up  To redesign a synthesis to produce a chemical in larger formation of a product. amounts. A process might be scaled up first from a laboratory method reactants  The chemicals on the left-hand side of an equation. These to a pilot plant, then from a pilot plant to a full-scale industrial chemicals react to form the products. process. reacting mass  The masses of chemicals that react together, and the sensory neuron  A neuron that carries nerve impulses from a receptor masses of products that are formed. Reacting masses are calculated to the brain or spinal cord. from the balanced symbol equation using relative atomic masses and serotonin  A chemical released at one type of synapse in the brain, relative formula masses. resulting in feelings of pleasure. reaction (of a surface)  The force exerted by a hard surface on an object shell  A region in space (around the nucleus of an atom) where there can that presses on it. be electrons. reactive metal  A metal with a strong tendency to react with chemicals short-term memory  The part of the memory that stores information for such as oxygen, water, and acids. The more reactive a metal, the more a short time. strongly it joins with other elements such as oxygen. So reactive simple reflex  An automatic response made by an animal to a stimulus. metals are hard to extract from their ores. slope  The slope of a graph is a measure of its steepness. receptor  The part of a control system that detects changes in the system and passes this information to the processing centre. small molecules  Particles of chemicals that consist of small numbers of atoms bonded together. Chemicals made up of one or more non- receptor molecule  A protein (often embedded in a cell membrane) that metallic elements and that have low boiling and melting points consist exactly fits with a specific molecule, bringing about a reaction in the of small molecules. cell. social behaviour  Behaviour that takes place between members of the recycling  A range of methods for making new materials from materials same species, including humans. that have already been used.288
  • 36. specialised  A specialised cell is adapted for a particular job. titration  An analytical technique used to find the exact volumes ofspectroscopy  The use of instruments to produce and analyse spectra. solutions that react with each other. Chemists use spectroscopy to study the composition, structure, and toxic  A chemical that may lead to serious health risks, or even death, if bonding of elements and compounds. breathed in, swallowed, or taken in through the skin.starch  A type of carbohydrate found in bread, potatoes, and rice. Plants transect  A straight line that runs through a location. Data on plant and produce starch to store the energy food they make by photosynthesis. animal distribution is recorded at regular intervals along the line. Starch molecules are a long chain of glucose molecules. transformer  An electrical device consisting of two coils of wire woundstarch grains  Microscopic granules of starch forming an energy store on an iron core. An alternating current in one coil causes an ever- in plant cells. changing magnetic field that induces an alternating current in thestatic electricity  Electric charge that is not moving around a circuit but other. Used to ‘step’ voltage up or down to the level required. has built up on an object such as a comb or a rubbed balloon. transmitter substance  Chemical that bridges the gap between twostem cell  Unspecialised animal cell that can divide and develop into neurons. specialised cells. trend  A description of the way a property increases or decreases along asterilisation  The process of making something free from live bacteria series of elements or compounds, which is often applied to the and other microorganisms. elements (or their compounds) in a group or period.stimulus  A change in the environment that causes a response. triplet code  A sequence of three bases coding for a particular amino acid in the genetic code.stomata  Tiny holes in the underside of a leaf that allow carbon dioxide into the leaf and water and oxygen out of the leaf. unspecialised  Cells that have not yet developed into one particular type of cell.strong (nuclear) force  A fundamental force of nature that acts inside atomic nuclei. unstable  The nucleus in radioactive isotopes is not stable. It is liable to change, emitting one of several types of radiation. If it emits alpha orstructural proteins  Proteins that are used to build cells. beta radiation, a new element is formed.subatomic particles  The particles that make up atoms. Protons, velocity  The speed of an object in a given direction. Unlike speed, which neutrons, and electrons are subatomic particles. only has a size, velocity also has a direction.surface area (of a solid chemical)  The area of a solid in contact with velocity–time graph  A useful way of summarising the motion of an other reactants that are liquids or gases. object by showing its velocity at every instant during its journey.sustainable  Able to continue over long periods of time. voltage  The voltage marked on a battery or power supply is a measuresynapse  A tiny gap between neurons that transmits nerve impulses from of the ‘push’ it exerts on charges in an electric circuit. The ‘voltage’ one neuron to another by means of chemicals diffusing across the gap. between two points in a circuit means the ‘potential difference’tarnish  When the surface of a metal becomes dull or discoloured between these points. because it has reacted with the oxygen in the air. voltmeter  An instrument for measuring the potential differencetheoretical yield  The amount of product that would be obtained in a between two points in an electric circuit. reaction if all the reactants were converted to products exactly as work  Work is done whenever a force makes something move. The described by the balanced chemical equation. amount of work is force multiplied by distance moved in the directiontherapeutic cloning  Growing new tissues and organs from cloning of the force. This is equal to the amount of energy transferred. embryonic stem cells. The new tissues and organs are used to treat working memory  The system in the brain responsible for holding and people who are ill or injured. manipulating information needed to carry out tasks.thermistor  An electric circuit component whose resistance changes xylem  Plant tissue that transports water through a plant. markedly with its temperature. It can therefore be used to measure yeast  Single-celled fungus used in brewing and baking. temperature. yield  The crop yield is the amount of crop that can be grown per area oftissue  Group of specialised cells of the same type working together to do land. a particular job. zygote  The cell made when a sperm cell fertilises an egg cell in sexualtissue fluid  Plasma that is forced out of the blood as it passes through a reproduction. capillary network. Tissue fluid carries dissolved chemicals from the blood to cells. 289
  • 37. Index abundant elements 146 babies 108, 198, 199 children 213 direct current (d.c.) 187 acceleration 85, 88 background radiation 264 chloride 145, 147 displacement reactions 53 acids 228­­–233 bacteria 16, 17, 20, 36, 37, 39, chlorine 49, 52, 53, 61, 62, 64, dissolved compounds 140, action-at-a-distance forces 263 65, 68, 69 147 77 balanced forces 82 chlorophyll 22 distance–time graphs 86, 87 active sites 18 ball-and-stick models 139 chloroplasts 22, 26, 34 distillation 38 active working memory 218, balloons 78 chromosomes 114–117, 119, disturbed habitats 33 219 base pairing 120, 121 126 division of cells 116, 117, 119 activity (radioactive decay) batteries 172–174, 178, 180, circuits, electric 169–183 DMSA chemical 272 270 181, 185 clones 108, 111, 128 DNA (deoxyribonucleic adaptations 32, 33 behaviour 196–198, 206, closed loop circuits 169 acid) 37, 108, 114–116, adenine (A) 120, 121 208–211 coils 184–187, 188 120–123, 125,126 adult stem cells 129 beta radiation 257, 261, 262 collision theory 242, 243 double helical structures aerobic respiration 34 bicycles 94, 95 combs 166 121 air bags 92 biofuel 38, 39 commutators 185 air resistance 83 blood cells 114 compasses 184 Earth 136–142, 146, 147, alcohol 37, 38 body temperature 19, 20 complex behaviour 197, 206, 150–155 alkali metals 48, 49 Bohr, Niels 58 210 eclipses 55 alkalis 228–230, 232 boiling points 140 compounds, ionic theory 65 Ecstasy 205 alpha radiation 257–259, 261, bonding 138, 139, 147, 156, 157 concentrated solutions 27 effectors 201–203, 206 262, 264, 265, 268 brain 194, 195, 206, 207 concentration 240, 241 egg cells 114, 118, 119, 128 alternating current (a.c.) branching of electric conditioning 208, 209 electrical power 182, 183 187 circuits 172 conduction 156 electricity 63–65, 140, 155, aluminium 146, 154, 155, 158, bromide 145 consciousness 206 156, 186–189 159 bromine 52, 53, 61 conservation of energy 99 circuits 164, 165 Alzheimer’s disease 214 building blocks 107 contact forces 77 ionic compounds 147 amino acids 18, 28, 122 bulk chemicals 226 contamination 265 motors 185 ammeters 171 Bunsen burner 54 conventional current 170 nuclear power 275 amoeba 196 burettes 235 coolants 275 electrodes 63, 154, 155 anaerobic respiration 36–39 copper 152, 157 electrolysis 63–65, 154, 155 animals 16, 34, 36, 208, 209, calcite 146 copying of DNA 121 electrolytes 154, 155 211 calcium carbonate 143 core of Earth 136 electromagnetic induction antibodies 124 calcium chloride 244 corrosive substances 52 186 argon 138 calcium fluoride 52 covalent bonds/structures electromagnets 184 asexual reproduction 117 cancer 129, 267, 269, 273 138, 148, 149 electrons 57–61, 148, 149, 167, atmosphere 136–139 carbohydrates 22, 23, 27 crumple zones 91, 92 168, 170 atoms carbon 137, 152 crust of Earth 136 elements 46–49, 137, 138, 146 carbon minerals 148, 149 carbon dioxide (CO2) 31, crystals 49, 62, 64, 65, 146, electrons 60, 61 chemical species 68 37–39, 138–140 147, 149, 155 halogens 52, 53 Earth 138, 139 carbon minerals 148, 149 curare (toxin) 205 ionic theory 65 electric charge 168 carbonates 143, 145, 231 current 168, 169–181 radioactive materials 256 electrons 58, 59 cars 38, 79, 85, 91–93 cuttings 111 embryos 108, 126, 127 halogens 52 catalysts 17–19, 240–242 cytoplasm 26, 34, 37, 123 endothermic reactions 236, ionic theory 66, 67 cells 16, 23, 26, 107–111, cytosine (C) 120, 121 237 masses 46, 153 114–119, 124–129 energy 16, 58, 96–99, 274, 275, nuclear fission 274, 275 cellulose 23 Dalton, John 56 278, 279 nuclear fusion 278, 279 central nervous system Darwin, Charles 113 body temperature 19 radioactive materials (CNS) 202, 203 daughter products 261 chemical reactions 236, 257–261, 270, 271 cerebral cortex 206 Davy, Humphry 64 237 structure 56, 57, 66, 67 CFCs (chlorofluorocarbons) decay (radioactive) 257, 261, metal extraction 151 ATP (adenosine 68 270 photosynthesis 23 triphosphate) molecules change of momentum 90 denaturation 20 respiration 34–37 35 charge 166–168, 278 development 104, 105 environment 32, 33, 134, 135, attractive forces 138, 166, chemicals 49–51, 134, 135, dialysis 244 151, 159 167 224–227 diamond 148, 149, 257 enzymes 17–19, 20–23, 122, auxins 111 energy 236, 237 diatomic molecules 52, 68 124, 126 average speed 84 patterns 44, 45 diffusion, plants 24–27, 30 epilepsy 207 axons 203–205 species 68, 69 dilute solutions 27 equations 50, 51, 90290
  • 38. Escherichia coli 196 glands 201 isotopes 262, 263, 266, methane 39ethanoic acid 242 glucose 22, 23, 27 270–273 mind 194, 195ethanol 37, 38 gold 146, 150 ITER nuclear fusion project minerals 28, 146, 148–150ethics 211 grafting procedures 128 279 mining 158excretion 16 graphite 148, 149 mitochondria 34, 37, 116exothermic reactions 236, grasping reflexes 198 jet engines 78 mitosis 116, 117 237 gravitational potential joules (J) 97 molecules 50, 52, 138, 139explosions 238 energy 97–99 molten salts 63extraction of metals 150–152, gravity 77, 83, 88 kinetic energy 96, 98 momentum 89–91, 94 154, 159 greenhouses 29, 31 knee jerk reflexes 198 motion 16, 74, 75, 94, 95eye 200, 202 groups (periodic table) 47, 61 motor neurons 202, 203 growth 16, 23, 104, 105 lactic acid 36 motors 184, 185Faraday, Michael 64 guanine (G) 120, 121 laws of motion 94, 95 movement 16, 74, 75fatty axon sheaths 203 learning 208–211, 212, 213 multistore memory modelsfeldspar (mineral) 146 habitats 32, 33 leaves 25–27 217female gametes 114, 118, Hadron Collider 57 leukaemia 129 muscles 201 119, 128 haematite 146 life processes 14, 15fermentation/fermenters hair cells 126 light intensity 29–31 National Grid 189 17, 38, 39 half-life 270, 271 light-dependent resistors natural environment 134,fetus 108 halogens 52, 53, 67–69 (LDRs) 176 135filament lamps 176 harmful substances 52 lightning 166 negative electric charge 166,fine chemicals 226 hazards 265, 266, 276, 277 limestone 143, 146, 231, 234 167fireworks 76 Health Protection Agency limiting factors 31 negative ions 65, 67flame colour 54 (HPA) 265, 266 line spectra 54, 55, 58 nerve cells 107, 203flies 106, 197 heating 174 liquids 51 nerve impulses 201–205fluorine 52, 53, 61 helium 54, 55, 278, 279 lithium 48, 49, 54, 61 nerve pathways 212, 213fluorite 52 high-level waste (HLW) 276, lithosphere 136, 137, 146, nerves 203food 16, 19 277 147, 150–155 nervous system 201–203football 90 hormones 201 living things 16, 17 neurons 202–205, 212, 13forces 88–90, 94, 95, 138, 166, human simple reflexes lock-and-key models 18 neutralisation reactions 167, 278 198–201 long-term memory 214, 218 232, 233 friction 80, 81 hydrogen 50, 51, 58, 138, 139, Low-Level Waste (LLW) 276 neutrons 57, 260 magnets 184 232, 238, 278, 279 lubricants 149 newborn reflexes 198, 199 motion 76, 77 hydrosphere 136, 137, lung cancer 267, 269 newts 110formula mass 140, 153, 248 140–142 nitrate ions 28formulae 51 hydroxides 144, 231, 232 magnesium chloride 141 nitrogen 28, 137, 138, 140freefall 83, 88 magnesium sulfate 244–247 non-metalsfriction 80, 81, 94 imaging techniques 207, 211, magnetic resonance chemical species 62–65,fuel 38, 39 272 imaging (MRI) 207, 211 67–69, 141–147functional magnetic impulses 112, 113, 206 magnets 77, 184, 186, 187 Earth 138 resonance imaging indicators 230 mains electricity 188 halogens 52, 53 (fMRI) 207 industry (chemical) 226, male gametes 114, 118, 119 periodic table 47fungi 37 227, 242 malleable metal properties Nuclear Decommissioning information 216, 217, 218 156 Agency (NDA) 276, 277gametes 114, 118, 119, 128 inheritance 120, 121 mantle of Earth 136 nuclear fission 274, 275gamma radiation 257, 262, innate behaviour 198 mass 248, 249 nuclear fusion 278, 279 263, 272 insoluble carbohydrates 27 MDMA (Ecstasy) 205 nuclear power 274, 275gases 24–27, 30, 51, 63, 68 instantaneous speed 85 medical imaging 207, 211, 272 nuclear waste 276, 277 Earth 138 interactions 76–79 meiosis 119 nuclear weapons 274, 275 fuel 39 intermediate-level waste melted ionic solids 147 nuclei 34, 56, 57, 114, 115 radioactive materials (ILW) 277 melting points 156 plant cells 26 267 involuntary reflexes 196–201 membranes 26, 34, 37 radioactive materials reaction rates 238, 239 iodide 145 memory 210, 214–219 257–261, 270, 271, 274,generators 168, 186, 188, 189 iodine 52, 53, 61, 273 Mendel, Gregor 120, 121 275, 278, 279genes 114, 115, 125–127 ionising radiation 256, 263, Mendeleev, Dmitri 46 ‘Nun Study’ (brain) 214genetic switches 125–127 267 meristem cells 109, 111 nutrition 16genetic variation 119 ions 28, 64–67, 146, 147, 155 messenger RNA (mRNA) 123germanium 46 chemical species 69 metals 46–49, 62–66, 141–147, Ohm’s law 175, 176giant covalent structures salts 141–145, 232, 233 150–159 orbits 58 148, 149 iron 152 acids 230, 231 ores 146, 150–152, 154, 158,giant ionic lattices 147 iron sulfide 62 chemical species 69 159giant sequoia tree 109 irradiation 263, 265 halogens 53 organelles 22, 26, 34, 37, 116 291
  • 39. organs 107, 200–202, 206 radioiodine treatment 273 sequoia tree 109 technetium-99m ovaries 118 radiotherapy 273 series circuits 171, 178, 180 (radioactive tracer) oxides 150, 231 radon 267–269, 271 sex cells 114, 118, 119, 128 270–273 oxygen 22, 34, 35, 50, 51, random quadrat placement sexual reproduction 118, 119 temperature 19–21, 29, 240, 137–140, 146 33 shells 58, 60, 61 241 ozone layer 68 rate of photosynthesis 29–31 short-term memory 214, 216 testes 118 reactants 50 silica 146 testing water 142 parallel circuits 172, 178, 181 reacting masses 248, 249 silicon 146 theoretical yield 249 pathways (neurons) 212, 213 reaction rates 20, 21, 238–241 silicon dioxide 149 therapeutic cloning 128 Pavlov’s experiments 208 reaction of surfaces 82, 83 simple behaviour 206 thermistors 176, 177 Penfield, Wilder 207 reactions (neutralisation) simple reflexes 196–201, 202 thymine (T) 120, 121 percentage yield 249 232, 233 skin stem cells 128 thyroid cancer 273 periodic table 46–49, 52, 53, reactive metals 150, 154 slope 86 tissues 107 60, 61 receptors 200, 202, 203, 206 slowing down 95 titrations 234, 235 periods (periodic table) 47, 60 recycling 159 small molecules 138 toxic substances 52, 68, 205 peripheral nervous system red blood cells 114 social behaviour 210 transects (samples) 33 203 reduction reactions 150–152 sodium 48, 49, 59, 61, 62, 64, transferring energy 96 pH 21, 230 reflex arcs 202 65, 69 transformers 188, 189 phloem 26, 107 reflexes 196–201, 208, 209 sodium chloride 62, 64, 65, treatment (medical) 272, 273 photosynthesis 16, 22, 23, 25, rehearsal-based memory 218 69, 141, 142, 146, 147 trends (chemical 26, 29–31 relative atomic mass 46, 153 sodium hydroxide 144 properties) 49 phototropism 112, 113 relative formula mass 153, sodium sulfate 141 physical properties (alkali 248 soil minerals 28 ultraviolet (UV) radiation metals) 49 relay neurons 202 ‘solar system’ models 258 68 pigment 22 repetition-based learning solids 51 undisturbed habitats 33 plant (chemical industry) 213, 218 solubility 27, 142, 143 unspecialised cells 110 226 reproduction 16, 117–119 solution salts 63 unstable nuclei 257 plants 16, 17, 22–36, 107, repulsive forces 166, 167, 278 specialised cells 107, 110, uracil (U) 123 109–113, 117 resistance 83, 173–177, 181 124–127, 203 plasma 279 resistors 174, 176–178, 181 spectra 54, 55, 58 vacuoles 26 plastics 166 respiration 16, 23, 34–37, 126 spectroscopy 54, 55 van de Graaff generators polymers 35 responses to stimuli 16, 196 speed 84, 85, 98 168 positive charge 166, 167, 278 retrieval of information 216, speed–time graphs 87, 88 variable resistors 176, 177 positive ions 65, 66 217 sperm cells 114, 118, 119 velocity 85 potassium 48, 49, 61 ribosomes 123 spheres of Earth 136–142, see also speed potassium chloride 141 risk 93, 245, 265, 266, 269, 146, 147, 150–155 voltage 173, 179, 186–189 potential difference (p.d.) 276, 277 starch molecules 23, 27 voltmeters 179 179–181 RNA (ribonucleic acid) 123 startle reflexes 199 potential dividers 180 rockets 78 state symbols 51 walking palm tree 112 potential energy 97–99 rocks 137, 143, 146 static electricity 167 walls 83 power, electrical 182, 183 root hair cells 28 steel 159 waste 16, 39, 276, 277 power stations 188, 189, 274, rooting powder 111 stem cells 108, 110, 128, 129 water 30, 48, 137, 138, 275, 278, 279 rooting reflexes 199 stepping reflexes 198 140–143, 147 precipitates 143–145 rubbing (charge) 166 sterilisation (radioactive chemical equations 50, products 50, 246, 247 Rutherford, Ernest 258, 259 materials) 263 51 proteins 18–23, 28, 122–127 stimuli 16, 196, 200–204, 212, diffusion 24, 25 proton numbers 57, 60 safety 91–93, 265, 266, 276, 213 watts (W) 182 protons 57, 260 277 stomata 26, 27, 30 weather 141, 166 pupil reflexes 198 salivary gland cells 126 strong metal properties 156 work 96–99, 183 purity (chemical) 234, 235, salts 49, 62–65, 140–147, structural proteins 124 working memory 218, 19 246, 247 230–233 sucking reflexes 199 pyrite 62, 146 samples 32, 33 sulphates 145 xylem 26, 107 sea water 141, 146 Sun 55, 278 quadrats 32, 33 seat belts 92 surface areas 240, 241, 243 yeast cells 37, 38, 117 quartz 146 sedimentary rocks 143 surface reactions 82, 83 yield 29, 247, 249 Sellafield (reprocessing survival in nature 196, 197 radiation, chemical species site) 277 sustainability 38 zinc 152 68 sense organs 200, 202, 206 swimming reflexes 199 zinc chloride 63 radiation dose 264, 265 senses 16 synapses 204, 205 zinc ions 144 radioactive decay 257, 270 ‘sensory homunculus’ 206 zygotes 108, 118, 119 radioactive materials 254, sensory memory storage 215 tables 82, 83 255 sensory neurons 202 tarnish (metals) 48292
  • 40. AppendicesUseful relationships, units, and data C6 Chemical synthesis actual yieldRelationships percentage yield 5​ ________________ ​ 3 100%       theoretical yieldYou will need to be able to carry out calculationsusing these mathematical relationships. P6 Radioactive materials Einstein’s equation: E 5 mc2, where E is the energyP4 Explaining motion produced, m is the mass lost, and c is the speed of distancespeed 5​ _________   ​  light in a vacuum. time change in velocityacceleration 5​ __________________        ​ Units that might be used in the time takenmomentum 5 mass 3 velocity Additional Science coursechange of momentum 5 resultant force 3 time for length: metres (m), kilometres (km), centimetreswhich it acts (cm), millimetres (mm), micrometres (µm), nanometres (nm)work done by a force 5 force 3 distance moved inthe direction of the force mass: kilograms (kg), grams (g), milligrams (mg)amount of energy transferred 5 work done time: seconds (s), milliseconds (ms)change in gravitational potential energy 5 weight 3 temperature: degrees Celsius (°C)vertical height difference area: cm2, m2kinetic energy 5 ½ 3 mass 3 velocity2 volume: cm3, dm3, m3, litres (l), millilitres (ml) speed and velocity: m/s, km/s, km/hP5 Electric circuits power 5 voltage 3 current energy: joules (J), kilojoules (kJ), megajoules (MJ), voltage kilowatt-hours (kWh), megawatt-hours (MWh) resistance 5​ ________   ​  current electric current : amperes (A), milliamperes (mA) voltage across primary coil _____________________________ ​ 5​         voltage across secondary coil potential difference/voltage: volts (V) number of turns in primary coil​ __________________________________ ​          resistance: ohms (Ω) number of turns in secondary coil power: watts (W), kilowatts (kW), megawatts (MW) radiation dose: sieverts (Sv) Prefixes for units nano micro milli kilo mega giga tera one thousand one millionth one thousandth 3 thousand 3 million 3 thousand 3 million millionth million million 0.000000001 0.000001 0.001 1000 1000 000 1000 000 000 1000 000 000 000 293
  • 41. Useful information and data sodium hydroxide NaOH, sodium chloride NaCl, sodium carbonate Na2CO3, sodium nitrate NaNO3, P4 Explaining motion sodium sulfate Na2SO4, potassium chloride KCl A mass of 1 kg has a weight of 10 N on the surface of the Earth. magnesium oxide MgO, magnesium hydroxide Mg(OH)2, magnesium carbonate MgCO3, magnesium C5 Chemicals of the natural chloride MgCl2, magnesium sulfate MgSO4 environment calcium carbonateCaCO3, calcium chloride CaCl2, Approximate proportions of the main gases in the calcium sulfate CaSO4 atmosphere: 78% nitrogen, 21% oxygen, 1% argon, and 0.04 % carbon dioxide. Qualitative analysis data Tests for negatively charged ions P5 Electric circuits mains supply voltage: 230 V Ion Test Observation carbonate add dilute acid effervesces, 2– CO 3 P6 Radioactive materials and carbon dioxide gas is speed of light (c) = 300 000 000 m/s produced (the gas turns lime Chemical formulae water milky) C4 Chemical patterns chloride (in acidify with dilute nitric white solution) acid, then add silver nitrate precipitate water H2O, hydrogen H2, chlorine Cl2, bromine Br2, Cl– solution iodine I2 bromide (in acidify with dilute nitric cream lithium chloride LiCl, lithium bromide LiBr, solution) acid, then add silver nitrate precipitate lithium iodide LiI Br– solution sodium chloride NaCl, sodium bromide NaCl, iodide (in acidify with dilute nitric yellow sodium iodide NaI solution) I– acid, then add silver nitrate precipitate solution potassium chloride KCl, potassium bromide KBr, sulfate (in acidify, then add barium white potassium iodide KI solution) chloride solution or barium precipitate SO42– nitrate solution lithium hydroxide LiOH, sodium hydroxide NaOH, potassium hydroxide KOH Tests for positively charged ions C5 Chemicals of the natural environment Ion Test Observation nitrogen N2, oxygen O2, argon A, carbon dioxide CO2 calcium add sodium white precipitate sodium chloride NaCl, magnesium chloride MgCl2 Ca2+ hydroxide solution (insoluble in excess) sodium sulfate Na2SO4, magnesium sulfate MgSO4 copper add sodium light-blue precipitate Cu2+ hydroxide solution (insoluble in excess) potassium chloride KCl, potassium bromide KBr iron(II) add sodium green precipitate Fe2+ hydroxide solution (insoluble in excess) C6 Chemical synthesis chlorine Cl2, hydrogen H2, nitrogen N2, oxygen O2 iron(III) add sodium red–brown precipitate Fe3+ hydroxide solution (insoluble in excess) hydrochloric acid HCl, nitric acid HNO3, sulfuric zinc add sodium white precipitate (soluble acid H2SO4 Zn2+ hydroxide solution in excess, giving a colourless solution)294
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Winters/Science Photo Library; P51: Don Grall, Visuals Unlimited/ Fotolia; P260: Istockphoto; P263t: Shutterstock; P263b: Geoff Tompkinson/Science Photo Library; P52: Claude Nuridsany Marie Perennou/Science Science Photo Library; P265: Science Photo Library; P266: Josh Sher/SciencePhoto Library; P53: Andrew Lambert Photography/Science Photo Library; Photo Library; P266b: Health Protection Agency/Science Photo Library; P267:P54: David Taylor /Science Photo Library; P55l: Dept. Of Physics, Imperial Health Protection Agency/Science Photo Library; P272: Prof. J. Leveille/ScienceCollege/Science Photo Library; P55r: Roger Ressmeyer/Corbis; P57: David Photo Library/Science Photo Library; P274: Rex Features; P275t: Science Photo 295
  • 43. Library; P275b: Ria Novosti/Science Photo Library; P276t: Steve Allen/ Authors and editors of the first edition Science Photo Library; P276b: Science Photo Library; P278: European We thank the authors and editors of the first edition, Jenifer Burden, Simon Space Agency/Science Photo Library; P282: Geoff Tompkinson/Science Carson, John Holman, Anna Grayson, Angela Hall, John Holman, Andrew Photo Library. Hunt, Bill Indge, John Lazonby, Allan Mann, Jean Martin, Robin Millar, Nick Owens, Stephen Pople, Carol Tear, and Linn Winspear. Illustrations by IFA Design, Plymouth, UK, Clive Goodyer, and Q2A Media. Many people from schools, colleges, universities, industry and the professions The publisher and authors are grateful for permission to reprint the contributed to the production of the first edition of these resources. We also following copyright material: acknowledge the invaluable contribution of the teachers and students in the Although we have made every effort to trace and contact all copyright Pilot Centres. holders before publication this has not been possible in all cases. If The first edition of Twenty First Century Science was developed with support notified, the publisher will rectify any errors or omissions at the earliest from the Nuffield Foundation, The Salters Institute, and The Wellcome Trust. opportunity. A full list of contributors can be found in the Teacher and Technician resources. Project Team acknowledgements These resources have been developed to support teachers and students The continued development of Twenty First Century Science is made possible undertaking the OCR GCSE Science Twenty First Century Science suite by generous support from: of specifications. They have been developed from the 2006 edition of the · The Nuffield Foundation resources. · The Salters’ Institute We would like to thank David Curnow and Alistair Moore and the examining team at OCR, who produced the specifications for the Twenty First Century Science course.296
  • 44. GCSEadditionalscienceFOUNDAT NFOUNDATION ATION Twenty First Century Science is a suite of the new suite provides ideal support for the 2011 specifications offering flexibility and choice for every specifications, with updates including: student. GCSE Additional Science is: concept-led course developed to meet the needs assessment throughout the course of candidates seeking a deeper understanding of basic scientific ideas all abilities studies, when studied with GCSE Science. resources The Twenty First Century Science specifications and the and ideas. Oxford resources that support them have been developed in close collaboration between OCR, the This book is endorsed by OCR for use with modules University of York Science Education Group, the B4, C4, P4, B5, C5, P5, B6, C6, and P6 of the OCR Nuffield Foundation Curriculum Programme, and Twenty First Century Science GCSE Additional Oxford University Press. Science specifications. The fully revised second edition builds on the success It develops understanding of science concepts and of of this hugely popular suite of resources. Using how science works using relevant and engaging extensive feedback from teachers using the resources, science. What’s on the cover? Emiliania huxleyi – A species of single-celled plankton from a group GCSE GCSE additional additional GCSE GCSE called the coccolithophores, which additional additional science science science science uses photosynthesis to generate HIGHER FOUNDA FOUNDATION DAT N ATION workbook workbook HIGHER FOUNDAT N FOUNDATION ATION energy. Studying coccolithophoreGCSE Additional Science GCSE Additional ScienceHigher Student Book Foundation Student Book GCSE Additional Science GCSE Additional Science fossils allows scientists to reconstruct9780199138210 9780199138203 Higher Workbook Foundation Workbook the temperature and salinity of ancient 9780199138265 9780199138258 oceans for climate-change studies. The image is a false-colour scanning electron micrograph. GCSE GCSE additional additional science science resources planning s g exam assessment assessment essment ipack OxBox CD–ROM OM OxBox CD–ROM Box CD–ROM GCSE GCSE additional GCSE GCSE additional science Additional Additional science resourc resources planning pack rces planning pack g a k revision guide guide uide Science Science Exam Resources Preparation GCSE Additional Science Planning iPack Assessment GCSE Additional Science GCSE AdditionalResources Planning OxBox OxBox Revision Guide Science OnlinePack 9780199128518 CD-ROM CD-ROM 9780199138241 Homework 9780199138227 9780199138234 9780199128327 How to get in touch: ISBN 978-0-19-913820-3 web www.oxfordsecondary.co.uk email schools.enquiries.uk@oup.com tel 01536 452620 fax 01865 313472 9 780199 138203

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