Gr7 Sources of Energy & Potential & Kinetic Energy PDF

Unit 1 Renewable and non-renewable sources of energy What you already know ffi In previous grades you will have been introduced to the concept of energy. You learnt that energy is needed to do work. Energy can occur in several different forms such as electrical energy, potential energy and kinetic...

Unit 1 Renewable and non-renewable sources of energy What you already know ffi In previous grades you will have been introduced to the concept of energy. You learnt that energy is needed to do work. Energy can occur in several different forms such as electrical energy, potential energy and kinetic energy. You also learnt about energy systems. Energy systems are systems that can store and release energy. Energy system s have an input, a process and an output. People need energy for their daily activities. 1. What is potential energy? 2. What is kinetic energy? 3. What type of energy can be changed to allow you to see? 4. What type of energy can be changed to enable you to feel? 5. What type of energy can be changed so that you can hear? 6. Name three uses of electrical energy in your house. y 7. 8. What is an energy system? . What effect does a change in one part of a system have on the rest 0 ~ the system? . ... Lesson 1 No n-r en ew ab le sources of energy use _the Sun as an Ene rgy is the abi lity to do work. Green pla nts foo d the y eat. ene rgy source. Animals get the ir energy from the l or electrical Ma chi nes and electrical devices need mechanica ene rgy to work. make energy A sou rce of energy is a sys tem tha t is used to as a source of do work. For example, a wind turbine_uses wind Sources of energy energy to ma ke electrical energy or electricity. ed renewable tha t can be replaced, like wind energy, are call be replaced sources of energy. Sources of energy tha t can not ble sources of onc e the y have been used are called non-renewa energy, for example fossil fuels. No n-r ene wa ble sources of energy se fuels formed Fossil fuels include oil, coal and natural gases. The als. These millions of years ago from dead plants and anim rs of soil and organisms died and were buried under many laye rock caused the rock. Gre at .pressure built up by these layers of learn more abo ut organic ma tter to turn into oil and coal. You will this process in Topic 15. South Africa uses coal to generate mo st of its electricity and par t of its liquid fuels such as paraffin. Coal used to be a fairly che ap source of energy. Coal is a hard, bla ck . ca Figure q_ 1 An ope n cas t coa l min e in Sou th Afri • Topic q Sources of energy 0 substance made of carbon. Coal has to be dug out of the ground.(Figure 9.1). It is a non-renewable resource that will run out in the future. Using so much coal to power electricity stations has resulted in South Africa producing a lot of greenhouse gases that are harming the environment. The government wants to reduce the use of coal and find other sources of energy. Oil and natural gas are also fossil fuels and they cause the same problems as coal. Oil is like a liquid version of coal. Oil is pumped out of the ground and then transported vast -. Figure q_2 An oil mega tanker distances in huge oil transporting crude oil tankers (Figure 9.2). There is a risk of these tankers breaking up in rough seas, · causing extensive oil spills and widespread environmental pollution. Natural gas is made up mostly of methane. Methane is highly flammable. In natural gas wells, the gas rises up under its own pressure. Natural gas is often trapped within shale rock. . Frocking Figure q_3 An anti-tracking logo used by groups trying to protect the Karoo . ~ method of getting natural gas out of r~ck IS called hydraulic fracturing or frock" F k" . ing. roe mg involves pumping water sand d h . , an c em1cals into the shale at high pressure to crack open the rock and release the g as. Word bank resource: a supply of something that. can be Used when neected greenhouse gases: gases like carbon dioxide, methane and water vapour that trap heat in the atmosphere and reflect it back causing an increase In temperatures on the Earth flammable: easily able to catch fire or bum shale: a type of sedimentary rock in which oil and riatural gas can often be . found frocking: a process used to remove oil and natural gas layers of rock · pumpingw under press into it and th blasting the r lobbying: trying to influence people who make laws nuclear fission: the splitting of the nucleus of an atom Not only is natural gas a non-renewable energy source, but frocking is a very destructive method of extractin g the gas. The by-prod uct of frocking is water that is contami nated with extremely toxic chemicals. This water can also be set alight .due to the high amounts of methane in it. Overseas oil compan ies are lobbying for permission to do frocking in the Karoo. This has been met with a lot of opposition (Figure 9.3) as the Karoo is a very dry area and water is a valuable resource. Nuclear power An alternat ive way of producing energy is the use of nuclear power. Unstabl e radioactive material such as uranium is split in a process known as nuclear fission. This process releases large amounts of heat energy that can be used to produce electrici ty. The advanta ge is that this is 'clean' energy because no greenhouse gases are produced. Although uranium has to be mined and it is not a renewable source of energy, it is unlikely to run out in the near future. This form of energy is relatively cheap - although the initial cost of building a nuclear power station is very expensive. The disadva ntage of this method is that harmful radioact ive waste is produced. Getting rid of, or disposing of, radioactive waste is a problem. Radioactive waste is dangerous to. human health and the environment. Another disadva ntage is that there is a threat of nuclear meltdow n from power stations . This has raised concerns about the safety of using radioact ive material s to produce energy. Nuclear power has not lived up to its early promise of being the answer to decreasing fossil fuel supplies. South Africa has a nuclear power plant at Koeberg, just outside Figure q_4 Koeberg nuclear power station, close to Cape Town and Cape Town (Figure 9.4). Tobie Mountain • Topic q Sources of energy 8 1. 2. 3. 4. •-• Ill What is a non-renewable source of energy? Why are coal and oil considered to be Individual non-renewable sources of energy? What is nuclear fission? Draw a table like the one-shown in which you list the advantages and disadvantages of cool, oil, natural _ gas and nuclear power as sources of energy. •• -.- _•,,,. H•, •, • : • ,:· ,,!,:~:•·-~ i~,,_i_:1,•!r~··:..,__,1_1:_Ji,_;~---: . ~:,:Yf:.::..u;.~...... : Coal Oil I I r ' ; t f lI l Natural gas Nuclear . ~ Challenge . . . . ,' ··· .. //.': , .. , ,·;. ; Research _the issues about the. attempt by oil companies '. . . . ~. . . t~ do frocking in the·Karoo: _Wr,ite, a~ le~~t t~p paragr~p_hs in which you: . ., , . • e~plain what frocking is .·· · · -~ . . _ _. . • state whether you are. for.. or against the process of .. frocking and give reasons._ . ..._.....,._.L.."4Ai.,.....~ .••.;.--....,.___.._ -~.--~-,.__.,, .,. ..~--t._,_ .. ~ --: - Lesson 2 Renewable sources of energy . . A renewable energy source is a source of energy that can be reused, or replaced, once it has been used. This means that these are sustainable energy sources that we will be .able to use for a long time to come. Some renewable energy sources include hydropower, wind, sunlight and biofuel. sustainable: able to use continuously ·or maintain something at a , certain level and quality 8 • Topic q' Sources of energy • I l H y d ro p o w e r - H ~ ropower is also called h yd ro e le ct ri W a te r st o re d b e ii ci ty . nd a d a m wall flow hydros in to bi g turbines, in th e sa m e w a y th a el~ctricity: t w a te r was used to turn water wheel long a g o (Figure 9. electricity th a t s 5). The turbines ge nerate electricity us is made using th e moving water. ing T he a d va moving w at er to ntages of hydroele ctricity are th a t it d o e s n o t p tu rn turbines ollute th e environm ent and it is renewab le. The d is a d va n ta g e s of hydroelectricity are th a t dams disrup th e -n a tu ra l fl o w o t f rivers. South Afric a does n o t have en w a te r fo r large-sca ough le production of hyd ro e le ctricity but there ar several h yd ro p o w e e r schemes in Sou th A fr ic a. The largest is the Drakensburg Pum ped Storage Schem e th a t uses water fr om the Thukela River. \ : Figure q_s H ow hydroelectric power is m ad e Figure q_6 Wind tu rbines . o w e r - Huge wind turbines use wind W in d p . f~om any ~irection . re q 6). The energy to from the moving bl tu rn th e ir b la d e s ades (F1gu t .. l The advantage of this is used to p ro d u ce ty p e of elec net y. . ollu tio . n a n d it l is renewable. The e n e rg y ts th a t ~ p oduces no air P r . d turbines spoil the la d is a d va n ta g e s a re ndscape, th a t th e w tn 1· e q u ite . ea si ly . Another problem n ca tc h on tr m a ke a noise a n d ca . an birds th a t fly in is th a t th e tu rn in g to them. b la d e s ktll m Y Solar energy - The Sun's energy can be collected using solar cells called photovoltaic cells and converted into electricity (Flgure 9.1). The advantage of solar energy is that it is environmentally friendly, costs nothing and is renewable. One disadvantage is the expense involved in buying and setting up the cells. Another disadvantage is the fact that the system is less efficient on cloudy days. The manufacture of the solar panels requires the use of fossil fuels but this is a small consideration when . compared to the energy that the panels will produce once they are made. Figure q.7 Solar panels are useful in rural areas with no standard electricity supply. Here the solar panels ore being used to power a telephone. Biofuels - Certain plants, like sugar cane, sunflowers and com can be grown as sources of energy ,(Rgure q_a). This is done by fermenting the plant material to form ethanol. This is a good renewable source of energy. Figure q_a Some plants The disadvantage is that much con be grown and used to agricultural land which could be used produce biofuel. to grow food is now being used to grow biofuels. Many ecosystems are being destroyed and ·animal habitats lost as people clear land to plants oil-rich crops such as palm oil. This is threatening the survival of a number of species of plant and animals. Recently algae has been considered as an alternative plant source to produce biofuel. Another problem is that vehicles would need to have their engines converted to be able to run on biofuels. photovoltaic cells: · specialised panels that are adapted to absorb sunlight and convert it into electricity · biofuels: fuels that come from an organic · source such as plants or algae Wood - Wood is the fuel used by most low-income families (Figure 9.9). Wood could also be considered a biofuel. It is 0 renewable source of energy as long as the trees that are used up are replaced. ~ f;F-: G • Topic q Sources of energy Commercial plantat ions can provide a sustainable supply of wood. The problem with wood gathering ari~es when natural forests are chopped down for their wood and the trees are nC?t replaced .. Disadvantages of using wood as an energy source are that greenhouse gases are release~ when it is burned and deforestation can result from uncontrolled wood gathering. . Figure q_q A woman carries firewood back to her home to use as an energy source. ~-: -... ri·H•1ktltli,i~Mibiifi 1. 2. -----h What is a renewable energy source? A : A ":::::!I : \':::::!/ Give two examples. Pairs Draw a table like the one shown in which you list the advantages and disadvantages of each type of renewable energy source. I: Hydropower Wind Solar energy Biofuels - crops Biofuel - wood Challenge Choose a topic from the list below and research it using your library or the internet. Prepare a short talk to give to your class about your topic. • Find out about the impact of palm oil planta tions on the habita t of orangutans in Borneo. • Find out about the impact of wind turbines on the flight paths of migrating birds. • How do hydroelectric schemes disrup t the movements of fish such as salmon, which use the river~ on which they are situate d? • ·Investigate the problem of wind turbine s exploding and catchin g alight. • Topic q Sources of energy . 0 .......1111111 t • • t Energy i.s .needed·t o rnqke things work; • A source. ~nergy j s·a ··system ,that is used to chqnge energy into ~ work. For.example, the energy in moving woter can be 'tJseq to make electrical energy. There··are two .-.t,·ypes·, of energy sources - non. . renewable. arid ·renewable. There drff advdnt·a g_e s and disadvantages to using of· , • ) . • both types·of·energy · sources. Non-rene-Wable sb~rces of energy cannot be replaced·on.c e ·ttJeif-fl9ve·been used, for example foss_ il fuels·such-a·s ~·o i( :coar- anq natural gas and nuclear fuels such ,as uranium. Fossil fuels such ds coal_are mined and then burnt to produce electricity. · Burning fossil fuel~ _produces greenhouse gases that are harmful to the environment. The production of nuclear energy can also lead to . pollution and damage to the environm~nt. Renewable sources of energy can be continuously ·replaced, for example water, wind, sun and biofuels. Most renewable sources of energy are environmentally friendly. ,·. • • • • • • . wo·o d is often used as a fuel source in South Africa but it is only renewable if trees are replaced after they have been cut down. -Unit 1 Forms of energy: potential energy and kinetic energy - . ll What you already know In Grode 5 you learnt that energy is something that is needed to be able to do work. Energy can never be lost. It is simply _ changed from one form to·another. There are different forms of energy including chemical energy, light energy, electrical energy, sound energy, nuclear energy, heat energy, poten'ti~I erierini and movement or kinetic energy. . , t I , ,I .. , f, t ' I • • : 1 "4 .- Name three forms of energy. definition of the following terms: ' 2. Give. a . a) · -potential energy · · b) ·· kinetic energy 3. Give two examples of potential energy. 4. Give two examples of kinetic energy.' 1. ' . . - ~ ~: .,. "\ I • Lesson 1 Potential energy ·and kinetic energy system: a set of pdrts that . wor~ together · . to perform a . · function· transformed: changed or , .converted potential energy: energy that is stored in a system Systems con store and release energy. An energy system consists of different forms of energy that interact with one . another. Energy in a system con change from one form - to another form. For example, a wind turbine is a system. Energy from the wind is changed or transformed by th~ , .. _ wind turbine into electrical -~nergy. ·. · 1 ._ , , • , I I ~ Stored energy is energy that is 'waiting for something to happen'. Stored energy is called potential energy. Objects may have potential energy due to thei~ position above the ground - t~is is c~lled gravitational potential energy. • Topic 10 Potential and kinetic energ.y 8 Other objects may have potential energy due to the way the bonds hold their particles together. This is called chemical potential energy. When the bonds break apart, energy is released. Potential energy is available to be used. When it is used, it can be transformed into kinetic energy. This transfer of energy causes a change or movement within the system. · klneUc energy: energy which causes a change or movement Energy transformations Potential and kinetic energy transformations take place in many different systems. Some examples are: • Rubber bands - when a rubber band is stretched, it gains potential energy. When the rubber band is released, it springs back to its original shape. So much potential energy can be stored in a stretched rubber band that it can shoot across a room. • When skydivers go up into the air in an aircraft, they gain potential energy because of their position above Earth. When they jump from the plane, this potential energy becomes kinetic energy as they fall back to the ground. Books which are balanced on the edge of a table will have potential energy due to their position. When they fall off the table, the potential energy is transformed into kinetic energy. Electrical cells, also known as batteries, contain potential energy because of chemicals that are-,inside of them. When the chemicals react they are able to produce an electric current that is electrical energy. This energy will flow through a circuit system. Figure 10.1 A stretched rubber band • ~ • Figure 10.2 Skydivers falling to the ground Topic 10 Poteritial and kinetic energy . I Figure 10.3 Books balanced on the edge of a table • Figure 10.4 Electrical cells are full of stored energy. Figure 10.5 Chemical potential energy in fossil fuels is what enables cars to move. Fuel - in the last topic you learnt that the fuels used in vehicles are fossil fuels. Fossil fuels contain energy from ancient sunlight. Plants used the Sun's energy millions of years ago to make chemical energy by photosynthesis. When the plants and animals that ate them died, this chemical energy was stored as chemical potential energy for millions of years. Today we use stored chemical energy in fossil fuels like oil and coal to power machines and vehicles. 1. 2.. 3. 4. 5. [ii Name four forms of potential energy. Where does the energy in petroleum fuel lndlvldual cbme from? What gives an object gravitational potential energy? How do electrical cells produce an electric current? Define an energy system. • T~pic 10 Potential and kinetic energy G Lesson 2 Potential energy in food Word bank Joule: the All food contains potent ial energy. This energy originally standard unit Of measurement Of comes from the Sun and is changed into chemical potent ial energy energy by plants during photosynthesis. People eat these plants or they eat the animals that ate the plants. Either way, the potential energy in the food becomes available for people. In Grade 10 you will learn that the main source of energy used by the human body is carbohydrates. You will also learn that fats contain a lot more potential energy than carboh ydrate s but they are used as a reserve source of energy. Most foods are packaged ready for sale. There shoulq be a table on the packaging that lists the contents, togeth er with their energy conten t. The unit of measurement for energy is the Joule (J). The J?ule is written with a capital letter as it is named after James Presco tt Joule, a British physicist. Figure 10·6 Some examples of carbohydrates i 9 • Topic 10 Potential and kinetic energy