Edexcel IGCSE Physics 2013
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| 1347994658 | Describe the structure of an atom in terms of its protons, neutrons and electrons. | Protons are positively charged particles found in the nucleus; Neutrons are neutrally charged particles found bound with the protons in the nucleus; Electrons are negatively charged particles found in "orbit" around the outside of the atom. | 0 | |
| 1347994659 | State what is meant by an isotope. | An element which has a different number of neutrons from normal; also has the same number of protons; has the same chemical properties as the usual element; can be described as "heavy" or "light" depending on whether it has more or less neutrons. | 1 | |
| 1347994660 | Describe the nature of alpha particles. | High energy Helium nuclei; Has +2 electric charge due to lack of electrons; Has very poor penetrating power (stopped by skin, paper or air). | 2 | |
| 1347994661 | Describe the nature of beta particles. | High energy electrons; Has a -1 electric charge; Has moderate penetrating power (stopped by a sheet of metal or similar). | 3 | |
| 1347994662 | Describe the nature of gamma rays. | Wave of high frequency (small wavelength) electromagnetic wave; wave of energy and as such is massless; Has high penetrating power (can only be reduced in intensity by thick sheet of dense lead metal). | 4 | |
| 1347994663 | State what is meant by nuclear radiation. | A unstable atom will undergo a spontaneous and random process which results in the loss of energy (mass) in the form of alpha, beta or gamma decay. | 5 | |
| 1347994664 | State what is meant by unstable atom. | An unstable atom is one which does not have enough energy per nucleon with which to hold itself together resulting in it undergoing nuclear decay. | 6 | |
| 1347994665 | State 2 methods of detecting nuclear radiation. | Photographic film; Geiger-muller tube / Geiger-counter; | 7 | |
| 1347994666 | List the 5 sources of background radiation | Cosmic rays from space; Radon gas in the air seeping from the ground (biggest); Radioactive rocks and soil; Buildings; Food and drink (bananas!); | 8 | |
| 1347994667 | State what is meant by background radiation | Background radiation is a naturally occurring low-level source of nuclear radiation. | 9 | |
| 1347994668 | Define Half-life | The time it takes for the mass of a sample to reduce by half; OR the time it takes for the activity of a sample to reduce by half. | 10 | |
| 1347994669 | Describe the usage of radioactivity in medical and non-medical tracers. | A radioactive sample is ingested or injected into a person. It is a low-level source of beta radiation with a short half-life to ensure low risk. The path that the sample takes in the body can be tracked using medical equipment; A radioactive sample is injected into a supply of water. It is a low-level source of beta or gamma radiation with a short half-life to ensure low risk. The path that the sample takes, or where it leaks out into the ground water, can be tracked using equipment. | 11 | |
| 1347994670 | Describe the usage of radioactivity in radiotherapy. | Commonly known as Chemotherapy; A radioactive sample is mixed with a chemical which enhances its absorption by cells which are rapidly growing - such as cancer cells; The chemical is absorbed, and so is the radioactive sample; The radioactive sample accumulates in the cancerous cells killing them. | 12 | |
| 1347994671 | Describe the usage of radioactivity in carbon dating. | All living organisms absorb and release carbon dioxide from the air; Some of this carbon dioxide contains a radioactive isotope of carbon called carbon-14; Whilst living the level of carbon-14 remains constant; When dead the levels of carbon-14 decrease due to nuclear decay; Knowing the half-life of carbon-14 and the amount that is remaining scientists can estimate the time since the organism died. | 13 | |
| 1347994672 | List the 3 ways that radioactive decay is dangerous. | Radiation can cause mutations in living organisms; Radiation can damage / kill cells and tissues if absorbed in a high amount; Radioactive waste from power stations can leak out into the ground from their storage. | 14 | |
| 1347994673 | Describe the format of the Geiger-Marsden gold foil experiment. | A radioactive sample is used to produce a source of alpha particles; Alpha particles are channels and made to be directed towards very thin gold foil; The gold foil is placed in an evacuated chamber surrounded by a screen which glows when struck by an alpha particle. | 15 | |
| 1347994674 | Describe the experimental results of the Geiger-Marsden gold foil experiment. | Most alpha particles passed straight through the very thin gold foil as predicted by the Thomson "Plum Pudding" atomic model; Some alpha particles passed through and were deflected through large angles; A very few number of particles actually rebounded. | 16 | |
| 1347994675 | Describe how Rutherford's conclusions compare to the results of the gold-foil experiment. | Passed through - the atom is mostly empty space; Big deflections - nucleus contains all of the positive charge; Rebounds - nucleus is very small and contains all of the mass. | 17 | |
| 1347994676 | State what is meant by nuclear fission. | Nuclear fission is a nuclear reaction it is NOT nuclear decay; It is started by directing a neutron at an atom of Uranium-235; Neutron binds forming highly unstable Uranium-236; Uranium-236 disintegrates into 2 daughter nuclei also releasing 2-3 additional neutrons. | 18 | |
| 1347994677 | State what is meant by a 'chain reaction.' | The fission process both starts with and ends with neutrons; The neutrons released during the reaction can go on to further initiate additional fission reactions. | 19 | |
| 1347994678 | Describe the role of the moderator in a nuclear reactor. | The moderator is a substance which absorbs some of the KE of the fission neutrons produced; The absorption of KE causes the neutrons to slow down; and the moderator to heat up; Slower neutrons are more likely to cause further fission reactions, improving efficiency of the reactor; The heated moderator can be used to produce steam to generate electricity. | 20 | |
| 1347994679 | Describe the role of the control rods in a nuclear reactor. | The control rods can be raised or lowered into a nuclear reactor, creating a partition between nuclear fuel rods; The control rods are made of a substance which readily absorbs neutrons; When lowered, the control rods absorb the free neutrons reducing the amount of further fission reactions; This prevents the reactor overheating / meltdown due to excess fission reactions. | 21 | |
| 1347996098 | State what is meant by radioisotope. | It is an element with the same number of protons but different number of neutrons such that it is unstable. | 22 |
