Transcript
version 1.0
Entry Level Certificate
Science Notes on the Subject Content
TEACHERS’ GUIDE AQA Entry Level Certificate 4948
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Teachers’ Guide – General Certificate of Secondary Education – Science
Notes on the Scope of the Subject Content 10
Introduction The information presented in this section is intended to indicate the depth and breadth of teaching required for certain topics and should be used in conjunction with the statements of content and the guidance given in the specification. The numbers to the left of each subsection refer to the corresponding paragraph in the specification.
10.1
Unit 1 Keeping Healthy: diet, exercise, drugs and diseases How do diet, exercise and the use of drugs, alcohol and tobacco affect human health? What are the causes of diseases and what defences do humans have against them? Content Statement from Specification
5 •
Reflex actions are automatic and rapid.
6 •
A healthy diet contains the right balance of the different foods you need and the right amount of energy. Knowledge of different food types is limited to carbohydrates, fats and proteins and examples of sources of each. Knowledge of the effects of an unbalanced diet is limited to a person being too fat or too thin. No knowledge of deficiency diseases is required.
7 •
People who exercise regularly are usually fitter than people who take little exercise. The concept of fitness is limited to the rate at which the pulse rate returns to normal for a person after exercise.
8 •
Too much salt in the diet can lead to increased blood pressure, and processed food often contains a high proportion of salt.
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Additional Notes No knowledge of the details of the neurones of the reflex arc is needed. Candidates should know that the brain is often not involved. They should be familiar with a range of common reflexes, eg pupil reflex, dropping a hot object.
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Science – General Certificate of Secondary Education – Teachers’ Guide Content Statement from Specification
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Additional Notes Knowledge to include the fact that heroin and cocaine are illegal.
9 •
Drugs change the chemical process in people’s bodies so that they may become dependent or addicted to them and suffer withdrawal symptoms without them. Knowledge of specific drugs is limited to the fact that heroin and cocaine are very addictive.
10 •
Tobacco smoke contains substances that may cause cancer (carcinogens) and an addictive substance called nicotine. Candidates may be required to evaluate the different ways to stop smoking.
11 •
Alcohol slows down reactions, and too much may lead to lack of self-control, unconsciousness or even coma, eventually damaging the liver and brain. For example, look at the response of the iris to changing light intensity or the reaction to touching a hot object.
Alcohol slows reactions such as reflexes. Look at the potential dangers of driving a car whilst under the influence of alcohol linked to this slowing of reactions.
12 •
Bacteria and viruses may reproduce rapidly inside the body and may produce poisons (toxins) which make us feel ill. No recall of specific illnesses is required.
Poisons cause the symptoms of diseases, though no recall of specific illnesses is required.
13 •
White blood cells help to defend against bacteria by ingesting them.
In most cases, the effect of white blood cells prevents us from getting diseases or enables us to recover from diseases without the aid of drugs.
14 •
Antibiotics, including penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body, but cannot be used to kill viruses.
Painkillers reduce pain but only antibiotics kill the bacteria.
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Teachers’ Guide – General Certificate of Secondary Education – Science
10.1
Unit 2 Inheritance and Reproduction: the role of hormones, chromosomes and genes How do hormones affect processes within the human body? What is the role of the chromosome and the gene in the reproduction process? What is the difference between sexual and asexual reproduction? Content Statement from Specification
Additional Notes
5 •
Many processes within the body are coordinated by chemical substances called hormones. These are secreted by glands and are transported to their target organs by the bloodstream. No knowledge of the names of specific hormones is required.
6 •
Several hormones are involved in the menstrual cycle of a woman, including some that are involved in promoting the release of an egg. No further details of the menstrual cycle are required.
Candidates should know the basic details of the cycle, ie it lasts approximately 28 days, the egg is released around day 14 and menstruation (period) happens at the end of the cycle.
7 •
The uses of hormones in controlling fertility include giving oral contraceptives which contain hormones that inhibit eggs from maturing and giving ‘fertility drugs’ to stimulate eggs to mature. Neither the names of the hormones involved, nor the mechanism by which they work, is required. Candidates may be required to evaluate the benefits of, and the problems that may arise from, the use of hormones to control fertility.
Look at examples such as oral contraceptives have a high success rate but can cause side effects and that fertility drugs can enable childless couples to have a baby but increase the chance of multiple births.
8 •
Knowledge is required about the information that results in plants and animals having similar characteristics to their parents being carried by genes.
Genes are passed to baby animals through eggs and sperm or to seeds through pollen and ovules.
9 •
Different genes control the development of different characteristics.
Most genes have several forms, eg a gene for tongue rolling could code for the ability to roll the tongue or the inability to do this. There are different genes for each feature of a living organism.
10 •
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Sexual reproduction involves the mixture of genetic information from two parents leading to variety in the offspring.
Mendelian genetics and ideas of dominance and recessiveness are not required. Candidates should understand that a gene for a particular characteristic could come from either parent, that offspring have a mixture of genes from both parents and that siblings are different from one another even though they have the same parents. Knowledge of the formation of identical twins is not required.
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Science – General Certificate of Secondary Education – Teachers’ Guide Content Statement from Specification
11 •
In asexual reproduction, only one individual is needed as a parent.
Additional Notes Examples of asexual reproduction are limited to cuttings and simple divisions of yeast. Asexual reproduction leads to the production of offspring that are identical to the single parent.
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12 •
New plants are produced quickly and cheaply by taking cuttings from older plants.
13 •
In genetic engineering, genes are transferred to cells of other organisms.
14 •
Genes are able to be transferred to the cells of animals and plants at an early stage in their development so that they develop with desired characteristics.
No knowledge of mechanism is required. Genes may be removed, replaced by others or new ones added. These genes may come from animals, plants or bacteria.
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Teachers’ Guide – General Certificate of Secondary Education – Science
10.1
Unit 3 Evolution and Environment: competition, adaptation and pollution What determines where particular species live? How do humans affect the environment? Content Statement for Specification
Additional Notes
5 •
Plants often compete with each other for light and for water from the soil.
6 •
Animals often compete with each other for food, mates and territory.
7 •
Animals and plants may be adapted for survival in the conditions where they normally live. For example, polar bears in the Arctic, cacti in deserts.
8 •
The theory of evolution states that all species of living things have evolved from simplest life-forms which first developed billions of years ago.
9 •
Extinction may be caused by changes to the environment. Examples – changes to climate or food supplies.
10 •
Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste. Candidates may be required to analyse and interpret scientific data concerning environmental issues.
Look at the importance of recycling in reducing the amount of waste dumped.
11 •
Waste may pollute water with sewage, fertiliser or toxic chemicals.
Consequences of this pollution are limited to the fact that the pollutants may kill living organisms.
12 •
Waste may pollute air with smoke and gases such as sulfur dioxide which contributes to acid rain.
Waste gases are limited to carbon dioxide and sulfur dioxide. Knowledge of acid rain is limited to the fact that it can kill living organisms.
13 •
Waste may pollute land with toxic chemicals, such as pesticides and herbicides, which may be washed from land into water.
Consequences of this pollution is limited to the fact that the pesticides and herbicides may kill living organisms for which they were not intended.
14 •
Increasing levels of carbon dioxide and methane in the atmosphere may be causing global warming by increasing the ‘greenhouse effect’.
Carbon dioxide comes from burning and methane from cows.
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Look at the idea that many changes in living things over millions of years has resulted in the animals and plants in the world today. Evidence for evolution comes from fossils. These show us what animals were like, that are now extinct.
Cutting down trees means that less carbon dioxide is used. No knowledge of how the greenhouse effect causes global warming is required.
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Science – General Certificate of Secondary Education – Teachers’ Guide
10.1
Unit 4 Products from Rocks: building materials and the use of metals How do rocks provide building materials? How are metals used? Content Statement for Specification
5 •
6 •
7 •
Additional Notes
All substances are made of atoms. A substance that is made of only one sort of atom is called an element. There are about 100 different elements, which can be shown in the periodic table, most of which are metals.
No knowledge of the structure of atoms is required.
When elements react, their atoms join with other atoms to form compounds.
No knowledge of bonding is required.
Limestone, containing the compound calcium carbonate, is quarried and can be used as a building material.
Candidates should be able to recognise a substance such as calcium carbonate as a compound from its chemical name.
Candidates should know that atoms may be represented by chemical symbols or as dots or spheres in diagrams, but are not expected to know the chemical symbols for particular elements.
Candidates should know the terms ‘reactant’ and ‘product’ as applied to a chemical reaction. They should know that chemical equations can be written in words and/or symbols to represent reactions, but knowledge of chemical symbols or formulae is not required.
Candidates should consider the impacts of quarrying, limited to damage to habitats, air pollution, dust, noise, traffic and employment.
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8 •
Limestone and its products have many uses, including the making of mortar, cement, concrete and glass. No knowledge of the production process is required.
Candidates should know that mortar is made by missing sand with lime or cement and water, cement is manufactured from limestone and concrete is made by mixing sand, cement and gravel with water. Candidates should be aware of examples of the uses of these materials and glass.
9 •
Ores contain enough metal to make it economical to extract the metal. Unreactive metals, such as gold, are found in the Earth as the metal itself, but most metals are found as compounds that require chemical reactions to extract the metal.
The names of particular ores are not required.
10 •
Candidates may be required to evaluate the social, economic and environmental impacts of recycling metals.
Knowledge of recycling is limited to aluminium, iron and copper. Candidates should be aware of the following reasons for recycling: metal ores are limited resources, much energy is needed to extract metals from their ores, and mining or quarrying metal ores impacts on the environment.
11 •
Most iron is converted into steels. Steels are alloys since they are mixture of iron with carbon and other metals.
Knowledge of the composition of specific examples of steel is not required, but candidates should be able to recognise a material as a steel from information about its composition.
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Teachers’ Guide – General Certificate of Secondary Education – Science Content Statement from Specification
12 •
Many metals in everyday use are alloys. Pure iron, copper, gold and aluminium are too soft for many uses and so are mixed with small amounts of other elements to make them harder for everyday use.
13 •
Copper has properties that make it useful for electrical wiring and plumbing. These properties are limited to its ability to conduct electricity easily and the ease with which it can be worked.
14 •
Low density and resistance to corrosion make aluminium a useful metal. No knowledge of the extraction process of aluminium is required.
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Additional Notes Candidates should have the opportunity to consider some of the principal uses of these metals and their alloys.
Candidates should be familiar with some of the uses of aluminium and its alloys, limited to aircraft, buildings, cookware and packaging.
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Science – General Certificate of Secondary Education – Teachers’ Guide
10.1
Unit 5 Oils: uses of crude and plant oils What do humans use crude oil for? What are the environmental effects of using fuels? How can plant oils be used? Content Statement for Specification
Additional Notes
Crude oil is a mixture of a very large number of compounds, and may be found in deposits underground. For example, the oil fields under the North Sea.
Candidates should know that crude oil is a fossil fuel.
The compounds in crude oil may be separated into fractions. This process, which takes place in a refinery, can be used to produce a range of useful fuels and oils.
Fuels and oils limited to petroleum gas (LPG), petrol, kerosene, diesel oil, lubricating oil and bitumen.
7 •
The gases released into the atmosphere when a fuel burns may include carbon dioxide, water (vapour), carbon monoxide and sulfur dioxide. Candidates may be required to evaluate the impact on the environment of burning fossil fuels.
Candidates should know which of these gases contribute to global warming and to acid rain formation.
8 •
The poisonous gas carbon monoxide is produced when fuels burn in a limited supply of air.
Candidates should know the terms ‘reactant’ and ‘product’ as applied to a chemical reaction. They should also know that chemical equations can be written in words and/or symbols.
5 •
6 •
No knowledge of particular oil fields or of the nature of oil accumulations is expected.
Details of the process of fractionation are not required.
No knowledge of chemical symbols or formulae is expected but candidates may be expected to interpret simple word equations involving not more than four entities.
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9 •
Crude oil is the raw material used to make polymers such as poly(ethene).
Candidates should know that most polymers consist of long chains of atoms or molecules and that many polymers are useful as plastics. The names of particular polymers and plastics, other than poly(ethene) are not required.
10 •
Poly(ethene) has many useful applications because it is waterproof and resistant to chemicals, eg packaging materials, moulded containers.
Candidates should know some of the common uses of poly(ethene).
11 •
Many polymers are not biodegradable. They are not broken down by microorganisms, which can lead to problems with waste disposal.
Candidates should appreciate the problems caused by plastics in litter and that recycling plastics is difficult. Knowledge of plastic waste disposal is limited to landfill sites, incineration, and recycling.
12 •
Vegetable oils are important foods and fuels as they provide a lot of energy.
Candidates should know that vegetable oils and fats provide more energy than the same mass of either carbohydrates or proteins.
Candidates should appreciate the relationship between use, property and cost.
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Teachers’ Guide – General Certificate of Secondary Education – Science
13 •
Oils do not dissolve in water, but can be used to make emulsions. Examples of emulsions are limited to salad dressings and ice cream.
Content Statement from Specification
14 •
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Artificial colours added to food can be detected by chromatography.
Candidates should be encouraged to make some emulsions and should be aware of their appearance and thickness compared with water. Additional Notes Candidates should have done some simple paper chromatography of coloured substances and should be able to interpret the results by comparing the position of the spots produced on the chromatogram.
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Science – General Certificate of Secondary Education – Teachers’ Guide
10.1
Unit 6 Earth and Atmosphere: changes past, present and future What are the changes in the Earth and its atmosphere? Content Statement for Specification
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Additional Notes
5 •
The Earth’s crust and the upper part of the mantle are cracked into a number of large pieces, called plates. Candidates should be familiar with a simple model of the Earth, as consisting of a crust, mantle and core.
Candidates should know that the crust is relatively thin, but other knowledge of composition or dimensions is not expected.
6 •
Convection currents within the Earth’s mantle cause the plates to move at speeds of a few centimetres per year.
Candidates should know that the mantle is sufficiently fluid to permit plate movement. They should be familiar with the shape of a simple convection current.
7 •
Earthquake and/or volcanic eruptions occur at the boundaries between these plates, although scientists cannot accurately predict when these will occur.
Candidates should know that small but instantaneous movements between plates cause earthquakes. Candidates should have seen maps showing the distribution of earthquakes and volcanoes and may be asked to interpret such maps. Candidates should know that lines of volcanoes occur at plate boundaries.
8 •
The proportions of different gases in the Earth’s atmosphere are about four-fifths (80%) nitrogen, about one-fifth (20%) oxygen, with small proportions of other gases, including carbon dioxide, water vapour and noble gases.
9 •
The noble gases are all chemically unreactive, and are used in filament lamps and discharge (fluorescent) tubes.
Candidates should have seen examples of filament and neon or fluorescent lamps. They should know that a noble gas prevents the filament from burning in a filament lamp and that in discharge tubes the noble gas changes electrical energy into light.
10 •
Helium is much less dense than air, and is used in balloons.
Candidates should know that helium is used in balloons where there is a risk of fire because it does not burn, whereas hydrogen burns in air or explodes.
11 •
Intense volcanic activity during the first billion years of the Earth’s existence released the gases that formed the early atmosphere and water vapour that condensed to form the oceans.
Candidates should know that the Earth’s early atmosphere was mainly carbon dioxide and water vapour.
12 •
Plants produced the oxygen that is now in the atmosphere, by a process called photosynthesis.
Candidates should know that photosynthesis is a process unique to green plants, enabling them to make foods in the presence of sunlight and that this process uses carbon dioxide and produces oxygen.
13 •
Most of the carbon from the carbon dioxide originally in the atmosphere millions of years ago gradually became locked up in rocks as carbonates and fossil fuels.
Candidates should know that oil, coal and natural gas are fossil fuels, and were formed from animal and plant remains. They should also know that limestone is a sedimentary rock that is mainly calcium carbonate.
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Teachers’ Guide – General Certificate of Secondary Education – Science Content Statement for Specification
14 •
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Nowadays, the release of carbon dioxide by burning fossil fuels increases the level of carbon dioxide in the atmosphere. Candidates may be required to evaluate the effect of human activities on the atmosphere.
Additional Notes Candidates are expected to know that carbon dioxide contributes towards global warning and should also be aware of some of the consequences of global warming.
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Science – General Certificate of Secondary Education – Teachers’ Guide
10.1
Unit 7 Energy Transfer: how energy is transferred and efficiency How is heat energy transferred? What affects the rate of transfer of heat energy? What is meant by the efficient use of energy? Content Statement for Specification
5 •
Thermal (infra red) radiation is the transfer of energy by electromagnetic waves, and no particles are involved in the transfer. No definition of the term ‘electromagnetic wave’ will be required.
Additional Notes Candidates should know that this is the method by which thermal energy travels from the Sun to the Earth. Other examples of thermal radiation include electric radiant heaters and fires.
6 • All bodies emit and absorb thermal radiation.
Candidates should appreciate that whether a body is a net absorber or emitter depends upon whether it is hotter or colder than its surroundings.
7 •
No quantitative relationship is required, but candidates may be required to interpret cooling curves.
The hotter a body is the more energy it radiates.
8 • Dark, matt surfaces are good absorbers and
Candidates may be required to relate this knowledge to applications such as the fins of a transistor heat sink being painted dull black, the advantage of solar panels being painted matt black, or the inside of a vacuum flask being a light, shiny colour.
9 • Transfer of energy by conduction and
Candidates should appreciate that, in conduction, energy is passed through a material from particle to particle, while, in convection, particles of the material circulate in convection currents.
good emitters of radiation. Light, shiny surfaces are poor absorbers and poor emitters of radiation.
convection involves particles. No knowledge of the mechanism of how this transfer takes place will be required.
Applications of thermal transfer by conduction and convection may be exemplified by insulation of the home, eg double-glazing, loft insulation, cavity wall insulation, draught prevention and by a study of how a vacuum flask prevents heat transfer. Candidates should also know that generally metals are good conductors and non-metals are good insulators.
10 • The bigger the temperature difference
between a body and its surroundings, the faster the rate at which heat is transferred.
No quantitative relationship is required, but candidates may be required to interpret cooling curves. Applications may include, eg the idea that turning down the thermostat in the home reduces the rate at which heat is lost.
11 • Candidates may be required to describe the
intended energy transfers/transformations and the main energy wastages that occur in a range of devices. This requirement is limited to the conversion of electrical energy into other forms, eg light bulb, radio, television, hair dryer.
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Teachers’ Guide – General Certificate of Secondary Education – Science Content Statement from Specification
12 • When energy is transferred/transformed, only part of it may be usefully transferred/transformed, thus leading to the idea of efficiency.
Additional Notes No knowledge of the equation for efficiency will be required, only the idea that when we move energy from one place to another, or change it from one form to another, it usually does not all end up where we want it or in the form that we want it. No calculations involving efficiency will be required, although candidates may be required to extract or interpret information from a pie chart, Sankey diagram or table.
13 • Energy which is not transferred/transformed
Candidates should be familiar with the concept of energy conservation, ie the idea that energy that is ‘wasted’ does not disappear, but simply changes into a non-useful form. Examples may include ‘heat’ produced by light bulbs, or by friction between moving parts of a machine.
14 • The greater the percentage of the energy that
Candidates could compare the advantages and disadvantages of ‘long life’ domestic lamps. Other examples could include the ‘energy efficiency’ stickers fixed to domestic appliances such as washing machines and fridges.
in a useful way is ‘wasted’, usually in the form of ‘heat’ (thermal energy).
is usefully transformed in a device, the more efficient the device is, eg filament lamps and fluorescent tubes. No calculations involving efficiency will be required.
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Science – General Certificate of Secondary Education – Teachers’ Guide
10.1
Unit 8 Electrical Energy: generation of electricity and useful electrical devices Why are electrical devices so useful? How should we generate the electricity we need? Content Statement for Specification
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Additional Notes
5 •
The domestic electricity meter measures the amount of electrical energy used in ‘units’ (kilowatt-hours). No calculations of kilowatt-hours will be required, nor will any calculations involving the cost of electricity by required.
Candidates should appreciate that electricity supply companies charge for each unit used.
6 •
The amount of electrical energy a device transforms depends on how long the appliance has been switched on and the rate at which the device transforms energy (ie the power rating). Heating devices generally have a higher power rating than other electrical devices. No calculations of the amount of electrical energy will be required.
Candidates may be required to compare the relative amounts of energy transformed by devices of different power ratings switched on for differing amounts of time.
7 •
The power of an appliance is measured in watts (W) or kilowatts (kW). No calculations of electrical power will be required.
Candidates should appreciate that the higher the power rating of a device, the faster the rate at which it transfers energy.
8 •
In most power stations an energy source is used to heat water, and the steam produced drives a turbine which is coupled to an electrical generator. No knowledge of the internal construction of these units will be required.
Candidates may be required to interpret a flow diagram, ie water is heated in a boiler to produce steam, steam at high pressure forces the blades of a turbine to rotate and this then rotates the moving part of a generator. The generator transforms movement energy into electrical energy.
9 •
Common energy sources include coal, oil, gas and nuclear fuel. Coal, oil and gas are burnt to produce heat. Nuclear fission of uranium/plutonium produces heat. No knowledge of the fission process is required.
10 •
Energy from renewable sources can be used to drive turbines directly. Knowledge required is limited to wind and water turbines.
Candidates should be familiar with the concept of wind farms and hydroelectric schemes.
11 •
Electricity can be produced directly from the Sun’s radiation using solar cells.
Examples of practical applications, such as for traffic signs and parking meters, or regions remote from a mains supply. Examples of situations where only a very small current is required, eg cameras, calculators.
12 •
In some volcanic areas, hot water and steam rise to the surface. The steam is tapped and used to drive turbines. This is known as geothermal energy.
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Teachers’ Guide – General Certificate of Secondary Education – Science Content Statement for Specification
13 •
Using different energy resources has different effects on the environment. Knowledge of these effects is limited to atmospheric noise and visual pollution, and the destruction of wildlife habitats.
14 •
Candidates should be able to compare and contrast the particular advantages and disadvantages of using different energy sources to generate electricity. This is limited to a comparison between fossil fuels, nuclear and renewable resources.
Additional Notes
Limited to a comparison between fossil fuels (coal, gas and oil), nuclear (plutonium and uranium) and renewable resources (hydroelectric, wind turbines, geothermal, solar cells and solar panels). Fossil Fuels: Advantages: well-tried technology, fuels are easy to use. Disadvantages: supplies will run out, causes chemical pollution, eg by producing carbon dioxide and thermal pollution leading to global warming. Nuclear: Advantages: a large amount of energy is released from a small amount of material, no chemical pollution Disadvantages: danger of radiation escaping, problems with waste disposal as the waste can be highly radioactive Renewable: Advantages: running costs are lower, no thermal or chemical pollution Disadvantages: supplies may fluctuate, eg the wind does not always blow, they may spoil the appearance of the landscape, geographic limitations of geothermal and hydroelectric schemes, limited power output of solar cells, and the fact that the sun does not always shine
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Science – General Certificate of Secondary Education – Teachers’ Guide
10.1
Unit 9 Radiation and the Universe: uses and hazards of e-m waves and radioactive emissions What are the uses and hazards of the waves that form the electromagnetic spectrum? What are the uses and dangers of emissions from radioactive substances? Content Statement for Specification
Additional Notes Candidates should be able to recognise a diagram of a transverse wave, and be able to identify the wavelength, measured in metres. They should understand that frequency is the number of wave cycles passing a given point each second, and is measured in Hertz.
5 •
Electromagnetic radiation travels as waves and moves energy from one place to another.
6 •
All types of electromagnetic waves travel at the same very high speed through a vacuum. Knowledge of the magnitude of the speed will not be required.
7 •
The electromagnetic spectrum is continuous but the waves within it can be grouped into types of increasing wavelength and decreasing frequency – gamma rays, X-rays, ultraviolet rays, visible light, infra red rays, microwaves and radio waves. No quantitative values of frequency or wavelength will be required.
Candidates should be able to recognise a diagram of the electromagnetic spectrum, and be able to group its constituent parts into the correct order according to wavelength or frequency.
8 •
Candidates may be required to state one use and one hazard associated with the use and type of radiation in the electromagnetic spectrum.
Examples may include the following: Radio: Use: TV and radio transmissions Hazards: some concern regarding development of cancers in people living very close to high-power transmitters – as yet unproven Microwaves: Uses: microwave cookers and mobile phones Hazards: leakage from microwave cookers, some concerns over prolonged use of mobile phones that may affect brain cells. Special concern regarding children, whose brains are still developing, as yet unproven Infra red: Uses: also known as ‘heat’ radiation, so used for warming Hazards: over exposure can damage the skin, eg sunburn Visible light: Uses: enables us to ‘see’ things, used by plants in photosynthesis Hazards: very bright light can damage the eyes; therefore we should never look directly at the Sun
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Teachers’ Guide – General Certificate of Secondary Education – Science Content Statement for Specification
Additional Notes Ultraviolet: Uses: sun-tan beds, detecting forged notes, ‘secret’ identity marking Hazards: ultraviolet in sunlight may cause skin cancer, hence the need for sun-screen creams X-rays: Uses: photographing broken bones, security scanning at airports Hazards: overexposure may cause cancers, hence the need for radiographers etc to be shielded Gamma rays: Uses: treatment of cancer patients Hazards: overexposure may cause cell damage and cancers
9 •
Radio waves, microwaves, infra red and visible light can be used for communication.
Radio waves are used for radio and television, microwaves for mobile phones, infra red for remote controls, burglar alarm sensors, and thermography, visible light for seeing and for use in cameras and telescopes.
10 •
Microwaves can pass through the Earth’s atmosphere and are used to send information to and from satellites and within mobile phone networks.
Candidates should be familiar with the idea of a geostationary satellite being used for satellite television.
11 •
Infra red and visible light can be used to send signals along optical fibres and so travel in curved paths.
Applications should include the use of endoscopes in the medical profession and the use of infra red signals in computer networking. No knowledge of the term ‘critical angle’ or ‘total internal reflection’ will be required, but candidates may be required to interpret or complete diagrams showing internal reflection along an optical fibre.
12 •
Candidates should be aware of the possible hazards associated with the use of different types of nuclear radiation, limited to the effect of the production of cancers.
No knowledge of the details of the effects on cells or DNA is required, other than the fact that cancers may be produced. Candidates should know the names of the three different types of nuclear radiation, ie alpha, beta and gamma, but are not required to know anything of their origin or composition. They should be aware that nuclear radiation is caused by the nucleus of an atom spontaneously disintegrating, but do not need to have any knowledge of how or when this occurs, nor any knowledge of half-life. They should know that an alpha source may be the most dangerous inside the body, but that a gamma source, because of its greater penetrating power, may be the most dangerous outside the body.
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Science – General Certificate of Secondary Education – Teachers’ Guide Content Statement for Specification
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Additional Notes
13 •
Knowledge is required as to the uses of nuclear radiation. This is limited to smoke alarms, radiotherapy treatment and tracers in medicine.
Candidates should be aware that an alpha source is often used in smoke detectors, that beta sources may be used as radioactive tracers and that gamma sources may be used for killing cancer cells.
14 •
Scientists are able to find out about the Universe by measuring the different types of radiation given out by the Sun and other stars.
Candidates should know that a star, such as our Sun, is a ball of very hot gases that gives off all kinds of electromagnetic radiation. They should know that, by studying the radiation from stars, scientists have been able to find out about the size and age of the Universe, and the fact that it appears to be expanding. No knowledge of how these facts have been determined (eg red shift) is required, but they should be aware of the fact that current estimates put the age of the Universe at about 15 billion years.
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