2ND E.S.O.
SCIENCE (Physics) BILINGUAL SUBJECT PROFESSOR NOTES
INDEX HANDY EXPRESSIONS IN ENGLISH CLASS................................................................................4 MEASURING......................................................................................................................................6 INTERNATIONAL SYSTEM OF UNITS......................................................................................7 Do you often get confused between mass and weight?...............................................................8 Volume is the amount of space an object occupies.....................................................................9 Density........................................................................................................................................9 ENERGY............................................................................................................................................11 TYPES OF ENERGY....................................................................................................................13 Kinetic Energy..........................................................................................................................13 Potential Energy........................................................................................................................14 ENERGY RESOURCES...............................................................................................................15 Renewable Energy....................................................................................................................15 Nonrenewable Energy...............................................................................................................15 You can get all this information – and more – from http://www.eia.gov/kids/.........................16 Efficiency of energy transfer.....................................................................................................17 The main fuels...........................................................................................................................18 The renewable fuels..................................................................................................................18 Energy word search........................................................................................................................20 PRACTICE WHAT YOU'VE LEARNED................................................................................20 ELECTRICAL ENERGY...................................................................................................................21 HOW THE ELECTRICITY SUPPLY WORKS............................................................................22 Generating electricity................................................................................................................22 The dynamo effect.....................................................................................................................22 Alternating current (a.c.) and direct current (d.c.)....................................................................24 ELECTRICAL ENERGY AND POWER......................................................................................25 TRANSFORMERS AND THE NATIONAL GRID.................................................................27 PLAY WITH ELECTRICITY FACTS......................................................................................29 How wind turbines generate electricity.....................................................................................30 How a coal power station works....................................................................................................31 How nuclear energy works............................................................................................................32 Hydroelectricity.............................................................................................................................33 HEAT..................................................................................................................................................35 THE EFFECTS OF HEATING......................................................................................................37 Specific heat capacity................................................................................................................37 Latent heat.................................................................................................................................38 HEAT TRANSFER........................................................................................................................40 Insulating homes.......................................................................................................................40 Geothermal energy process............................................................................................................42 How air conditioning works .........................................................................................................43 How to insulate your home.......................................................................................................44 WAVES...............................................................................................................................................45 DESCRIBING WAVES.................................................................................................................47 Transverse waves......................................................................................................................47 Longitudinal waves...................................................................................................................48 SEISMIC WAVES.........................................................................................................................49 How do we determine an earthquake's size?.............................................................................50 2nd ESO SCIENCE – professor notes
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PLATE TECTONICS AND VOLCANOS....................................................................................51 Sound and ultrasound................................................................................................................52 Electromagnetic waves..............................................................................................................52 WAVE BEHAVIOUR....................................................................................................................53 Reflection..................................................................................................................................53 Refraction..................................................................................................................................53 Types of Lenses.........................................................................................................................54 Absorption.................................................................................................................................55 LOUDNESS, PITCH AND QUALITY....................................................................................56 Kids Be Gone: High Pitch Only Teens Can Hear Used As Deterrent.......................................56 LIGHT AND COLOURS..........................................................................................................57 PLAY WITH THE FACTS OF LIGHT AND SOUND............................................................57 ELECTROMAGNETIC SPECTRUM SONG..........................................................................58 The Wonderful World of Colour...............................................................................................59 ROY G BIV SONG...................................................................................................................59 Solar Energy..............................................................................................................................60
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HANDY EXPRESSIONS IN ENGLISH CLASS •
•
•
•
Be missing / late. ◦ Who is missing today? - Pedro is missing today. ◦ Do you have the homework? - No, because I was missing last day. ◦ Why are you late? - I've overslept / I've been speaking with the teacher. ◦ If you are late, please knock the door before enter the room. ◦ I don't feel well. Can I go outside for a while? ◦ What's the matter? - I feel dizzy / I feel sick / I've got a headache [jedeik] Start an activity. ◦ Take out your notebooks. ◦ Please open your books to page... ◦ Pay attention, everybody! / Be quiet, please! / Stop talking! Shut up! ◦ Listen / read carefully. ◦ You have … minutes to do this exercise. ◦ First... then... finally... ◦ Is there any chalk? ◦ Sit properly! ◦ Stop making that noise! Common actions in class. ◦ Please, raise your hand / put your hand up if you want to say anything! ◦ Repeat with me: … ◦ Go out for five minutes! ◦ Point to / complete / match / answer / underline / put in order ◦ Come out to the front of the class / to the blackboard. ◦ Go back to your seat. ◦ Switch the computer on / off, please. ◦ Explain that in English. ◦ Make a sentence with this word. ◦ Clean the board, please. ◦ Rub out the first / last word. Rub out the whole sentence. ◦ Write your answer on the board. ◦ What can you see in this picture? Can you describe it? ◦ How do you spell …? ◦ Time is up! It's time to finish! ◦ Check your answers, please. ◦ I will collect your work in the end of the class. ◦ Don't forget to make the homework for tomorrow / for Monday! Be polite. ◦ Can you … please? - Of course! ◦ Thank you – You're welcome ◦ Can I go to the toilet, please?
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•
•
◦ Can I ask … for a pen / a pencil / a rubber / tippex? ◦ Can I give out / hand out the copies, please? ◦ I don't have a copy. Can you give me one, please? - Here you are. ◦ Can I / you shut the blinds, please? ◦ Can I open the window, please? ◦ Can I / you switch the fans on / off, please? ◦ Can I plug the charger of my computer? Understanding. ◦ Sorry? ◦ I don't get it. ◦ Can you repeat, please? / Can you play it again, please? ◦ Can you speak more slowly, please? ◦ Can you write it on the blackboard? ◦ Can you speak up, please? ◦ Can you turn up / down the volume, please? ◦ What is the meaning of …? ◦ How do you say … in English / Spanish? ◦ Can you give me an example? ◦ Do you know the meaning of …? - I have no idea. ◦ Any questions? Is it OK? Understood? That was good / bad. ◦ This is wrong. Be careful next time. ◦ Keep on trying. Try again. ◦ Not bad. Why don't you try …? ◦ Much better now / almost right ◦ OK / that's right / fine / well done / great! ◦ Impressive / brilliant / excellent / wonderful / perfect / fantastic / congratulations
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UNIT 0 MEASURING VOCABULARY •
matter
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quantity ≈ amount
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measurement → measure (verb)
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unit
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equation
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weight → weigh (verb) [uei]
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heavy (adj.)
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scale
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beam
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spring
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balance (noun & verb)
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would (auxiliary verb)
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gravity
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graduated cylinder
•
side
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INTERNATIONAL SYSTEM OF UNITS All physical quantities can be expressed in terms of seven base units, but this year we are going to use just five of them: Base quantity
Name
Symbol
Length or space (s)
Meter
m
Mass (m)
Kilogram
kg
Time (t)
Second
S
Electric current (I)
Ampere
A
Temperature (T)
Kelvin
K
Derived units Other quantities, called derived quantities, are defined in terms of the base quantities via a system of quantity equations. The derived units are obtained from these equations and the base units. Examples of these derived units are given in table 2. Derived quantity
Equation
Derived unit
Name
Area (surface)
S=bxh
m
2
Square meter
Volume
V = Ab x h
m
3
Cubic meter
Speed (velocity)
v=s/t
m/s
Meters per second
Acceleration
a=v/t
m/s2
Meters per second squared
Density
D=m/V
kg/m3
Kilogram per cubic meter
Force
F=mxa
kg·m/s2
Newton (N)
Pressure
p =F/S
kg/m·s2
Pascal (Pa)
Energy, work
E=Fxs
kg·m2/s2
Joule (J)
Electric voltage
V = E/I·t
kg·m /s ·A
Volt (V)
2
3
Mass is the amount of matter an object has. We often use a triple-beam balance to measure mass. A triple-beam balance gets its name because it has three beams that allow you to move masses along them. On the other side is a pan on which the object is placed. Here is a picture of a triple-beam balance. You probably have one in school.
A. The middle beam reads only in 100 g increments. B. The far beam reads only in 10 g increments. The weights in each of these beams must always sit in a "notch". They cannot be placed at arbitrary points on the beam. 2nd ESO SCIENCE – professor notes
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C. The weight on the front beam can be placed to read continuously from 0 to 10 grams.
If weighing an object directly on the pan, you must first zero the balance. Only if the balance is properly zeroed, will it weigh the object correctly. The triple beam balance has a little knob under the pan which you screw in or out to set the empty balance to read exactly 0.00 g. Rear weight is in the notch reading........... 70 g Middle weight is in the notch................... 300 g Front beam weight reads...........................3.3 g The can of soda weighs......................... 373.3 g You can practise this measurements with this link http://www.wisc-online.com/Objects/ViewObject.aspx?ID=GCH20
Do you often get confused between mass and weight? Shown below are two types of scales commonly used in the classroom -a spring scale (left) and a simple balance scale (right).
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Suppose we put an object that weighs 100 g on each scale. They both would indicate the same on Earth. Of course, to balance the scale on the right another 100 g mass is also needed. If we were to take both scales to the Moon, what would the spring scale read? How much mass would be needed to balance the 100 g mass on the balance scale? A spring scale would not measure 100 g, but a balance scale, which compares two masses, would measure the same. The moon has one sixth the gravity of earth. That means that the objects weigh less, and therefore they fall more slowly, but their mass still remains the same, because the mass is the amount of matter.
Volume is the amount of space an object occupies The volume of an object can be calculated geometrically using mathematical equations or by measuring liquid displacement. For example, you can measure the volume of a cube using the formula V = (side)x(side)x(side) or by using a graduated cylinder to measure liquid displacement. In the example below, the volume of the object is 40 – 30 = 10 mL.
Density Take a look at the two boxes below. Each box has the same volume, but a different number of molecules. If each molecule has the same mass, which box would weigh more?
The box with more balls has more mass per unit of volume. This property of 2nd ESO SCIENCE – professor notes
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matter is called density. The density of a material is the same in every portion of it, and helps to distinguish it from other materials. Since mass is usually expressed in grams and volume in cubic centimeters, density is expressed in grams/cubic centimeters. Remember that a cubic centimeter equals a mililiter. We can calculate density using the formula: Density = mass / volume
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UNIT 1 ENERGY VOCABULARY
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kind ≈ type1
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store (verb & noun) ≈ keep ↔ release (verb)
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supply (verb & noun)
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source [sors]. Example: there are primary sources (petroleum, sun, wind, rivers...) or secondary sources (electricity, hydrogen...)
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move (verb) → motion (noun)
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fast (adj.) - Example: the faster it moves, the more kinetic energy it has
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high (adj.) - Example: the higher the object, the more potential energy it stores
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change (verb & noun) ≈ turn into ≈ become ≈ is converted Examples:
Energy changes from kinetic to potential The solar panel turns light into heat Kinetic energy becomes / turns into potential energy Radiant energy is converted to / is turned into heat in a solar panel
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chemical (adj.) [kemical] → chemistry (noun) [kemistri]
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molecule [molekiul] = two or more atoms together
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bond
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fuels = fossil fuels (petroleum, gasoline US [gasolin] ≈ petrol UK2, coal, natural gas) or biofuels3 (ethanol, biomass, biodiesel [baiodi:sel], firewood...). The fuel of the future: hydrogen [jaidroyen].
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engine (noun) [enyin]. Example: a car with a diesel engine.
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burn (verb) → fire
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nucleus (singular) → nuclei (plural) [niucliai] → nuclear (adj.)
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uranium (iureiniom)
1 When not indicated, it is a noun. Or the same category as the precedent word. 2 UK United Kingdom, US United States 3 Bio [baio] means 'life'
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•
power ≈ energy, → powerful (adj.)
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power plant ≈ power station
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reservoir (noun) [reservuar] ≠ dam
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wave ≈ ray
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vibrate (verb.) [vaibreit]→ vibration (noun)
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light (verb & noun) → lightning
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sound (verb & noun)
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electrical (adj.) (from 'electron') → electricity (noun)
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wire (noun)↔ wireless (adj.)
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renewable [riniuabol] (from 'new') (adj.) ↔ nonrenewable
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generate (verb) ≈ produce ≈ make
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disadvantage ≈ drawback ↔ advantage [advantiy]
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environment [envaironment]
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pollution → pollute (verb)
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waste (verb &noun)
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run out (verb) ↔ remain
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TYPES OF ENERGY Energy is in everything. We use energy for everything we do, from making a jump shot to baking cookies to sending astronauts into space. Scientists define energy as the ability to do work because energy makes changes possible. Energy is needed for our bodies to grow and it allows our minds to think. For example, the food you eat contains chemical energy, and your body stores this energy until you use it when you work or play. We use energy to do things for us. It moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. Modern civilization is possible because we have learned how to change energy from one form to another and use it to do work for us and to live more comfortably. Forms of Energy Energy comes in different forms: • Heat (thermal) • Light (radiant) • Motion (kinetic) • Electrical • Chemical • Nuclear energy • Gravitational All these forms of energy can be put into two categories: potential and kinetic.
Kinetic Energy Kinetic energy is motion, like waves, electrons, atoms, molecules, substances, and objects. •
Radiant Energy is electromagnetic energy that travels in transverse waves. Radiant energy includes visible light, x-rays, gamma rays and radio waves. Light is one type of radiant energy. Sunshine is radiant energy, which provides the fuel and warmth that make life on Earth possible.
•
Thermal Energy, or heat, is the vibration and movement of the atoms and molecules within substances. As an object is heated up, its atoms and molecules move and collide faster. Geothermal energy is the thermal energy in the Earth.
•
Motion Energy is the energy needed to get an object moving. The faster
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it moves and the heavier the object, the more energy is stored. Wind is an example of motion energy. This energy is released when the object slows down. A dramatic example of motion energy is a car crash, when the car comes to a total stop and releases all its motion energy at once in an uncontrolled instant. •
Sound and other waves are the movement of energy through substances. Sound is produced when an object vibrates — the energy is then transferred to the molecules of the air, that vibrate too. Typically, the energy in sound is far less than other forms of waves.
•
Electrical Energy is delivered by tiny charged particles called electrons, typically moving through a wire. Lightning is an example of electrical energy in nature, so powerful that it is not confined to a wire.
Potential Energy Potential energy is stored energy. It depends on the position. •
Chemical Energy is energy stored in the bonds of atoms and molecules. Batteries, biomass, petroleum, natural gas, and coal are examples of stored chemical energy. Chemical energy is converted to thermal energy when we burn wood in a fireplace or burn gasoline in a car's engine.
•
Mechanical Energy is energy stored in objects by tension. Compressed springs and stretched rubber bands are examples of stored mechanical energy.
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Nuclear Energy is energy stored in the nucleus of an atom — the energy that holds the nucleus together. Very large amounts of energy can be released when the nuclei are combined or split apart. Nuclear power plants split the nuclei of uranium atoms in a process called fission. The sun combines the nuclei of hydrogen atoms in a process called fusion.
•
Gravitational Energy is energy stored in an object's height. The higher and heavier the object, the more gravitational energy is stored. When you ride a bicycle down a steep hill and pick up speed, the gravitational energy is being converted to motion energy. Hydropower is another example of gravitational energy, where the dam "piles" up water from a river into a reservoir.
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ENERGY RESOURCES When we use electricity in our home, the electrical power was probably generated by burning coal, by a nuclear reaction, or by a hydroelectric plant at a dam. Therefore, coal, nuclear and hydro are called energy sources. When we fill up a gas tank, the source might be petroleum or ethanol made by growing and processing corn. Energy Sources Can be Categorized As Renewable or Nonrenewable Energy sources are divided into two groups — renewable (an energy source that can be easily replenished) and nonrenewable (an energy source that we are using up and cannot recreate). Renewable and nonrenewable energy sources can be used to produce secondary energy sources including electricity and hydrogen.
Renewable Energy Renewable energy sources include: • Solar energy from the sun, which can be turned into electricity and heat • Wind • Geothermal energy from heat inside the Earth • Biomass from plants, which includes firewood from trees, ethanol from corn, and biodiesel from vegetable oil • Hydropower from hydroturbines at a dam Renewable energy sources account for just 7% of all energy used in the United States. Biomass, the largest renewable source, accounts for 53% (over half) of all renewable energy and 3.7% of total energy consumption. (Note: 53% of 7% is 3.7%.) Use of Renewable Energy Is Growing Renewable energy sources include biomass, geothermal energy, hydropower, solar energy, and wind energy. They are called renewable energy sources because they are naturally replenished. Day after day, the sun shines, the wind blows, and the rivers flow. We use renewable energy sources mainly to make electricity.
Nonrenewable Energy We get most of our energy from nonrenewable energy sources, which include the fossil fuels — oil, natural gas, and coal. They're called fossil fuels because they were formed over millions and millions of years by the action of heat from the Earth's core and pressure from rock and soil on the remains (or "fossils") of dead plants and creatures like microscopic diatoms. Another nonrenewable energy source is the element uranium, whose atoms we split (through a process called nuclear fission) to create heat and ultimately electricity. 2nd ESO SCIENCE – professor notes
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We use renewable and nonrenewable energy sources to generate the electricity we need for our homes, businesses, schools, and factories. Electricity "energizes" our computers, lights, refrigerators, washing machines, and air conditioners, to name only a few uses. Most of the gasoline used in our cars and motorcycles and the diesel fuel used in our trucks are made from petroleum oil, a nonrenewable resource. Natural gas, used to heat homes, dry clothes, and cook food, is nonrenewable. The propane that fuels our outdoor grills is made from oil and natural gas, both nonrenewable. Most of Our Energy Is Nonrenewable In the United States, most of our energy (93%) comes from nonrenewable energy sources. Coal, petroleum, natural gas, propane, and uranium are nonrenewable energy sources. They are used to make electricity, to heat our homes, to move our cars, and to manufacture all kinds of products. These energy sources are called nonrenewable because their supplies are limited. Petroleum, for example, was formed millions of years ago from the remains of ancient sea plants and animals. We can't make more petroleum in a short time. You
can
get
all
this
http://www.eia.gov/kids/
information
–
and
more
–
from
Nonrenewable sources affect the environment In our modern society we use a lot of energy resources. Some of them are used directly, especially oil – which is used as petrol and diesel for vehicles. A lot of our energy resources are used to make electricity, which we then use as a source of energy – so electricity is called a secondary energy source. How Are Secondary Sources of Energy Different? Electricity and hydrogen are different from the other energy sources because they are secondary sources of energy. Secondary sources of energy — energy carriers — are used to store, move, and deliver energy in easily usable form. We have to use another energy source to make electricity or hydrogen. In the United States, coal is the number one energy source for generating electricity. Today the cheapest way to get hydrogen is by separating it from natural gas, a nonrenewable energy source. Hydrogen can also be separated from water and from renewables, but hydrogen made from these sources is currently too expensive to compete with other fuels. Scientists are working on ways to make hydrogen from water and renewables more affordable. The drawbacks to nonrenewable energy sources are the amount of damage to the environment – the pollution. When we choose a fuel, we need to consider the effect on the environment, because some waste is toxic. Carbon dioxide is a waste product from using many fuels. Increased levels of carbon dioxide in the atmosphere cause some global warming. There is a lot of concern about climate change caused by global warming, so some countries, including the UK, are aiming to cut their emissions of carbon dioxide. The risks of using some energy resources are higher than others, but the risks to people because extended power cuts are also high – for example, failure of hospital equipment, 2nd ESO SCIENCE – professor notes
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no heating in the winter and no refrigeration in the summer.
Efficiency of energy transfer In a coal-fired power station, for every 100 J 4 of chemical energy stored in the coal that is burned, only 40 J is transferred to electrical energy. Energy is a conserved quantity, which means that the total amount of energy remains the same. It cannot be created nor destroyed. The 60 J of chemical energy that is not turned into electrical energy is wasted, and ends up as heat in the surrounding environment. This will cause a slight temperature increase in the surroundings. Energy becomes increasingly spread out and more difficult to use for further energy transformations. These energy transfers can be shown on a energy flow diagram: Energy as heat 60% Energy from coal 100%
Modern gas-fired stations. More of electrical energy. percentage, of the
Energy as electricity 40%
power stations are more efficient than coal-fired power the chemical energy stored in the gas is transferred to The efficiency of an energy transfer is the fraction, or energy input that is transferred to useful energy output: Efficiency=
useful energy output ¡100 total energy input
4 J stands for Jules, the international unit that measures the energy
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The main fuels Electricity can be generated in large power stations from many different types of fuel: •
Fossil fuels – coal, natural gas and oil. These fuels were formed from the remains of forest 300 million years ago. None is being formed today so they will eventually run out. When they are burned, sulphur dioxide gas is formed, which dissolves in rain to form acid rain. Coal produces more sulphur dioxide than oil, and gas produces less. All the fossil fuels produce carbon dioxide when burned.
•
Nuclear fuels – the nuclei of plutonium and uranium. These are radioactive elements, which means that they have a lot of energy inside and therefore they expel very energetic particles. Uranium is mined, but will not run out as quickly as fossil fuels. Plutonium is formed in nuclear reactors. If the plutonium is not processed into fuel, some of it can be used to make nuclear bombs. Energy is released when nuclear fission occurs – the nucleus splits in two new nuclei, that are still radioactive. One advantage is that no carbon dioxide is formed. But the main disadvantage is that the radioactive materials remain dangerous to living things for millions of years. These radioactive materials come from fuel production as well as from the waste fuel once it is used, and from the reactor when it reaches the end of its life. In addition, there is the risk of an accidental emission of radioactive material while the power station is operating. These concerns mean that there are high maintenance costs.
•
Renewable fuels. These are covered in the next section. They are fuels that are being made today and so will not be used up. Most of these are not used in large power stations. An exception is hydroelectric power, generated in some countries from the flow of large rivers and high waterfalls.
This table shows the fuels used in the UK for generating electricity: Fuels used in 2004
Percentage
Coal
40
Oil
<1
Gas
34
Nuclear
24
Hydroelectric
<1
Other renewables
<1
Imports (electric cable to France)
<1
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The renewable fuels Most of these fuels make use of the Sun's energy. It is the Sun that evaporates water and causes the rain to fill the rivers. It also causes convection currents that produce winds. The exceptions are geothermal, which results from radioactive decay inside the Earth, and tides, which are caused by the Moon. •
Hydroelectric power (HEP). Fast-moving water can be used to generate electricity. The UK does not have the large rivers needed to build large HEP stations, although there are some small ones in Scotland and Wales. There is no waste or pullution, but rainfall or snow is not constant so dams are needed. Building dams and flooding valleys and canyons changes the environment and causes conflict in some countries.
•
Wind turbines. These transfer the kinetic energy of the air into electrical energy. In 2006 there were about 1500 wind turbines in the UK, and the number is growing. Some areas, particularly offshore, are windy all year round. Wind turbines can be made rugged (tough) enough to last in these conditions. They do not produce polluting waste gases, but some people consider that they are noisy and make 'visual pollution'. Another disadvantage is that the wind is unpredictable and the amount of electricity generated will depend on the wind speed. Wind turbines take up a lot of space for the amount of electricity generated.
•
Solar cells. These are not used to turn generators. They produce electricity inside the cell. This means there is no need for overhead power cables. The electricity is direct current (DC) – the direction of the current does not change. There is no polluting waste and no need to buy fuel. There are no moving parts so they are rugged and do not need much maintenance. They have a long life. But they cannot produce power at night or in poor weather and are usually used to charge batteries. The big advantage is that they can be used in remote locations where there are no power lines.
•
Biomass fuels, for example wood, straw, manure5 or household waste. These are products that are being formed today by plants or animals. Power stations need a steady supply, and this is not the case, especially with plants. The fuels can be burned directly, or fermented to produce methane gas. Using them will produce carbon dioxide and ashes, but in many cases this pollution would be produced even if they were not used as fuel, due to rotting6.
•
Geothermal. There is a lot of heat below the Earth's crust. In the places where the heat is closer to the surface, geothermal power stations can use this heat. Examples are in New Zealand and Iceland. There is no pollution, although the effect of extracting the heat may change the environment, and these areas usually experience earthquakes and volcanic action, which may damage a power station.
•
Tides. In some places the change in the height of the water due to the tide is large enough to make it worth using to generate electricity. The
5 Animal excrements used to fertilize land 6 That is when bacteria and fungi eat the rest of other living things, producing its decomposition.
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tide does not depend on the weather. These areas are often important natural areas and holding back the water to run through turbines destroys the habitats of many birds and other animals.
Energy word search Match these sentences with the words that appear in the word search: 1. 2. 3. 4. 5. 6.
Place or thing from which we obtain something, like energy _______________ Barrier constructed to hold back water, forming a reservoir ___________ Material that is burned to produce heat ______________ Type of energy resulting from the movement of the electrons ______________ A place where something, as energy, is kept for future use ______________ Undulating motion that can transport energy, like the light, the sound or on the surface of the water _______________ 7. Container in which chemical energy is converted into electricity ______________ 8. Metal way used to carry electricity from one place to another ___________ 9. Wood that is burnt as fuel _____________ 10.A combustible black rock formed from plants and used as fuel ____________ 11.Highly flammable gas, obtained from water and used for nuclear energy and as fuel __________________________ 12.A large natural or artificial lake used as a source of water supply ___________ 13.Source of energy that does not run out when it is used ____________ 14.The smallest particle of a chemical element, the source of nuclear energy ________ 15.Type of energy stored in the bonds of atoms, like in the fuels or in the food ______________ 16.Allow to move or flow freely, like the water stored in a reservoir or the energy stored in an atom _____________________ 17.Radiation that usually comes from very hot things, like the sun or the fire ____________ 18.Type of energy that comes from the sun, from inside the earth and from fuels ___________
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PRACTICE WHAT YOU'VE LEARNED http://www.eia.gov/kids/energy.cfm?page=5
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UNIT 2
ELECTRICAL ENERGY VOCABULARY •
turn (verb & noun) ≈ rotate → rotation
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turbine
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blade
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generator
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dynamo [dainamou]
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magnet
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coil
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wire → copper wire
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steam
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boiler
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voltage → volts (V)
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current → amperes (A)
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frequency → hertz (Hz)
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power (≈power rating) → watts (W)
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cycle
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appliance
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rate
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cost (verb & noun)
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bill
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work out (verb) ≈ calculate
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step up ↔ step down (verb)
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increase ↔ decrease
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electrical grid ≈ mains U.K.
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HOW THE ELECTRICITY SUPPLY WORKS The electric current is the flow of electrons along the wires. The electric current is commonly called electricity. It needs to be generated either by a battery or a generator that give the electrons the energy they need. Electricity needs always two wires. One of them drives the electrons from the battery to the electrical appliance and the other drives them back. When a battery runs out of energy, it doesn't work any more, and it needs to be charged or replaced. On the contrary, the generator will go on working while it is attached to something that turns. A generator converts kinetic energy into electrical energy. The intensity of the current, or simply the 'current', is measured in amperes (A). This unit indicates how many electrons pass through a certain point of the wire in a second.
Generating electricity Turning a generator produces electricity. To turn the generators we connect them to turbines and we use all the different energy resources available to turn turbines. Wind and water flow can turn turbines directly. Steam is often used, produced by heating water. The heating is done by burning fuels, or using other heat sources. The diagram shows the parts of a coal-fired power station. In a modern gas-fired power station, the hot exhaust gases from the burners are used to turn the turbines, and then to heat water to steam which turns the turbines.
The dynamo effect The diagram shows how a voltage is induced in a coil of wire by moving a magnet into or out of a coil. Moving the coil instead of the magnet would have the same effect. This effect is used in dynamos and generators.
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The voltage is the amount of energy that the generator gives to the electrons. It is measured in volts (V). High voltage electric current may cause death, because it gives to you such amount of energy that your organs are literally 'roasted'. For example, a typical lightning bolt may carry an electric current of 300 kA7 and the voltage between the top of the cloud and the Earth may exceed a billion volts8 Low voltage electric current may cause contraction of the muscles, because the human brain uses electricity to give orders to them. That is why an electroshock can help reanimating people. However, a tiny voltage such as 1.5 V, like that of a battery, cannot have any effect on you. The dynamo effect occurs when a voltage is induced by: •
Moving a magnet near a coil.
•
Moving a coil near a magnet.
There are three ways to increase the induced voltage (and get greater induced current): •
Use stronger magnets
•
Use more turns of wire in the coil
•
Move the magnet (or the coil) faster.
The diagram shows a bicycle dynamo that uses a rotating magnet. As the magnet rotates faster, the induced current increases and the bicycle light gets brighter. An iron core is usually put inside the copper coil to reinforce the magnetic field.
7 kA stands for kiloamperes 8 A lighning needs at least 3 million volt per meter
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Alternating current (a.c.) and direct current (d.c.) Changing the direction of the magnetic field or the movement induces a voltage in the opposite direction. As the magnet rotates, the north pole and the south pole swap over once in each complete rotation. This means the direction of the voltage and the current changes. This is called alternating current (a.c.) Dynamos and generators produce alternating current (a.c.). Batteries and solar cells produce direct current (d.c.)
The d.c. can change only in voltage, but the a.c. can change in voltage and in frequency. In U.K., the a.c. generators at power stations that supply our mains electricity rotate 50 times in one second. This means that there are 50 complete cycles each second. The number of cycles per second is called the frequency. Frequency is measured is cycles per second or in hertz (Hz), where 1 Hz = 1 cycle per second. In U.S. and other countries they use a slightly different frequency, so the electrical appliances may not work properly if they have been made in other continent.
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ELECTRICAL ENERGY AND POWER We use electrical appliances at home to transfer energy from the mains supply to: •
heating
•
light
•
movement (including sound)
As you can see in this picture, sound is made by the movement of a loudspeaker cone. The alternating electric current that reaches the loudspeaker passes through the coil, and creates an alternating electromagnetic field9 that is attracted by the strong magnet every speaker has. The cone of the speaker is attached to the coil, so it vibrates at the same rate as the alternating current.
On the other hand, an incandescent bulb uses heat caused by an electrical current. When electrical current passes through a wire, it produces heat. The wire, or filament, gets so hot that it glows and gives off light. Common incandescent light bulbs have a filament made of tungsten. Since the hot tungsten would quickly burn away if it were exposed to oxygen, it must be placed in a sealed glass bulb which is either evacuated or filled with an inert gas that won't let it burn.
In two hours, an electric lamp transforms twice as much energy as it transforms in one hour. The power of an electrical appliance indicates how much electrical energy it transfers in one second – in other words, the rate al which it transfers electrical energy into other forms of energy. Energy is 9 When a coil acts as a magnet (thanks to the current that passes through it) it is called an 'electromagnet'
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measured in joules (J) whereas power is measured in watts (W). The equivalence between them is 1 W = 1 J/s10 Electrical power is calculated using: Power = current x voltage11 P = I·V Power is measured in watts (W), while current is measured in amperes (A) and voltage is measured in volts (V). As the voltage is the energy given to the electrons and the current is the number of electrons per second, the product of these magnitudes gives the energy per second. The amount of energy transferred from the mains appliance depend on the power rating of the appliance and the time for which it is switched on. Energy is measured in joules, but electricity suppliers sell us electrical energy in other units called kilowatt-hours. For example, electricity meters, like that of your house, measure the energy transformed using this unit. Electrical energy is calculated by Energy = power x time E = P·t There are two sets of units used for energy: The energy in joules (J), the power in watts (W) and the time in seconds (s)
or The energy in kilowatt-hours (kW h), the power in kilowatts (kW) and the time in hours (h)
The cost of each unit of electrical energy – which is one kilowatt-hour of electrical energy – varies. At the moment it is about 10 p 12. The electrical energy bill is calculated by working out the number of units used and multiplying by the cost of a unit: Cost of electrical energy used is calculated from: cost = power in kW x time in hours x cost of one unit or cost = number of kW·h used x cost of one unit For example: How much is the cost of using a 800 W microwave oven, if it is used for half an hour and the cost of a kW·h is 10p? cost = 0.8 kW x 0.5 hours x 10p/kW h cost = 0.4p
10 One watt equals one joule per second 11 Power equals current times voltage 12 12 euro cents, approximately
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Appliances used for heating have a much higher power rating than those used to produce light or sound. Tick in this list the household electrical appliances that produce mainly heat, and you will notice it! Appliance Incandescent light bulb TV Fan Clock radio Clothes dryer Desktop Computer Dishwasher Electric Blanket Electric Kettle Electric Mower Electric Shaver Fridge / Freezer Hair Blow dryer Home Air Conditioner Iron Laptop Computer Microwave Submersible Water Pump Toaster
Wattage 100W 150W 10W 1W 4000W 50W 1200W 200W 2000W 1500W 15W 500W 1000W 1000W 1000W 20W 600W 400W 800W
All values reported here are estimated, you should check the appliance labels to find out the correct power consumption. An important point to keep in mind is also the length of time for which the device will be used. For example an electric blanket may be used for 2 hours, but a hair drier for 5 minutes. Therefore the blanket uses 200W * 2 hours = 0.4kWh. The hair drier uses 1KW * 0.0833hours = 0.08333 kWh. So using the blanket costs roughly 5 times as much as the hair drier.
TRANSFORMERS AND THE NATIONAL GRID A transformer changes the size of an alternating current. The transformer will not work with direct current. That is one of the reasons we use an a.c. mains supply. You can also convert a.c. to d.c. with a rectifier, for example to charge the battery of a mobile phone. There are two types of transformers: step-up transformers increase voltage, and step-down transformers decrease voltage. The National Grid is the high-voltage electric power transmission network in Great Britain, connecting power stations and major substations and ensuring that electricity generated anywhere in England, Scotland and Wales 2nd ESO SCIENCE â&#x20AC;&#x201C; professor notes
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can be used to satisfy demand elsewhere. Therefore, the National Grid connects the suppliers of electricity – power stations 13 and the users of electricity – homes and workplaces. They are all connected together by power lines, some overhead and some underground or undersea. A National Grid has the following advantages: •
Power stations can be built where the fuel reserves are, or near the sea or rivers for cooling.
•
Pollution can be kept away from cities.
•
Power can be diverted to where it is needed, if there is high demand or a breakdown.
•
Surplus power can be used to pump water up into reservoirs to be used to generate hydroelectric power when there is a peak in demand.
•
Very large power stations can be built which are more efficient.
A National Grid has the following disadvantages: •
Power is wasted heating the power cables.
•
Overhead power cables are eyesore14.
•
Smaller generating projects such as wind turbines and panels of solar cells have difficulty competing with large suppliers.
13 Remember that in English you use a single dash (-) to clarify something. 14 Very ugly
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Reducing power loss in power lines. To supply 100 kW of power through overhead power cables we could transmit 1 A at 100 kV or 10 A at 10 kV. (Using P = I·V the power is P = 1A x 100 V = 100 kW or P = 10 A x 10 V = 100 kW) The power cables have a resistance to the flow of current. The heating effect in the cables depends on the resistance and on the current in the cables. •
We reduce the resistance of the cable by using thick copper, but the advantage of lower resistance has to be balanced against increased cost of cables and supports for the heavier cables.
•
By making the current as small as possible we can reduce the energy wasted as heat in the cables. The current can be small if the voltage is large.
When suplying power through cables, a large voltage allows us to use a small current and this reduces energy waste by reducing the heating of the cables. But high-voltage power lines can be very dangerous to people, birds and flying objects!
PLAY WITH ELECTRICITY FACTS Silicon spies http://www.engineeringinteract.org/resources/siliconspies/siliconspieslink.htm 2nd ESO SCIENCE – professor notes
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How wind turbines generate electricity 1.- First of all, watch the youtube video called 'How wind turbines work â&#x20AC;&#x201C; 3D animation' and put these words in the same order that they're pronounced for the first time. ELECTRICITY BATTERY
TURBINE ROTATES
PROPELLOR TURNS
GENERATOR CONVERTER
SPIN SHAFT
2.- Underline which of these words have something to do with 'wind power' and make short sentences. CURRENT MOTOR GENERATOR WINDMILLS
ROTOR STEADY SHAFT BLOWS
READY CURRY RENEWABLE ILLUMINATOR
POWER GRID GEAR BOX HIGH VOLTAGE WATERMILLS
3.- Complete the text with the missing words, while listening the video called 'How wind turbines generate electricity'. Complete also the two NUMBERS that appear. Finally, read it aloud. MISSING WORDS: cables rotor electricity electrical copper transformer increases direction energy spins turbine three blades shaft measure wind speed kinetic connects daily On top of each _________ is a box known as a nacelle. Attached to the nacelle, the ______ propellor like blades connect to a _______. Also on the nacelle is an anemometer to _________ the wind ________ and direction. The wind _______ rotates the nacelle to face it to the ______. The energy in the wind, called ________ energy, turns the turbine _______around the rotor, creating mechanical ________. The rotor connects to the main _______, which turns inside the generator housing. Here a magnetic rotor _______inside loops of copper wire. This causes electrons inside the ________to flow, creating electrical energy, what we call electricity in our ______lives. For this wind turbine, a step-up transformer inside the nacelle __________the electrical generation from (NUMBER) ________ volts to (NUMBER) ________ volts. The ____________ generated then travels down large cables from the nacelle through the tower and into underground ________. The cables takes the electricity generated from all the wind turbines to a sub-station. Here a step-up ____________again increases the electrical output. A transmission line ___________the electricity output at the sub-station to the __________ grids serving community throughout the region.
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How a coal power station works 1.- Put this words in the same order that appear in the following video, to form a sentence: (http://www.youtube.com/watch?v=SeXG8K5_UvU) (a) the energy / in essence / that converts / of electrons / from burning coal / it’s a factory / into a flow ________________________________________________________________________________ (b) into steam / coal / heat / from the burning / the intense / in the boiler / heats / and / the water / tubes / turns it ________________________________________________________________________________ (c) the blades / and flow / to spin / that pushes / of the turbine / it’s this pressure / causing it ________________________________________________________________________________ (d) to the rotor / of copper wire / large electromagnets / that is located / are attached / the stator / within coils / called ________________________________________________________________________________ (e) that can be / this produces / and / stepped up / transmission lines / through the station / transformers / sent / in voltage / from the station / electricity / across _________________________________________________________________________________ _______________________________________________________________________________ (f) to the boiler / from the turbine / from the lake / and / to continue / where it is / is condensed / reheated / the steam / the process / back to water / using cooling water / pumped back ________________________________________________________________________________ ________________________________________________________________________________
2.- Match each word at the left with its synonym. Then complete the sentences with them. huge tubes spins stations yard piles prior to furnace grind arrange
A. turns B. oven C. area D. pipes E. put F. lots G. facilities H. large I. before J. pulverize
(a) The _________ building you see behind me is one of Ontario power generation’s fossil fuel generating _________. (b)It is then transferred to the coal ______. (c) There large machines called tractor scrapers ________ the coal into storage _______. (d)It passes through enormous pulverizers that _______ the coal into a fine powder _______ burning. (e) The pulverized coal is fed into a large industrial _________ that is surrounded by boiler _______ filled with water. (f) As the generator rotor _______, a flow of electrons is created in the stator. 2nd ESO SCIENCE – professor notes
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How nuclear energy works First of all, it is a quite simple process, although it looks fairly complicated, it isn't really very _____________ at all. We require for generation of nuclear energy one of these substances: uranium, which is naturally occurring, and plutonium, which is the result of a working nuclear power station, it comes out as a by-product. Inside the nuclear power station there is a core of what we call a reactor. The core contains fuel rods, containing _________. These are the _____ of uranium within the core. Also in the ______ we need a thing called a moderator. This is to make the ________ work. Without the ____________, the uranium will not undergo this nuclear reaction and the whole thing won't work. The control rods can be pushed into the __________ reactor when it is working, and shut it down. And they do that by controlling the ________ in the core. All a nuclear reactor does this to produce HEAT. What we then have to do is to take the _______ away, and once we've taken it away, we can turn it into STEAM, which can drive a turbine which _______ a generator. This is exactly the same as in a conventional power station. Unlike most means of generating heat, the reactor is very economical on the amount of FUEL needed. For example, here 28 tonnes for a year of working, whereas a COAL power station will need 2000 __________ a week. We don't have large transportations of large ___________ of fuel. But the _____ is a fossil fuel, it's not renewable, it has very dangerous _____________, which have to be stored for a long period of time. But remember, there's only very small amounts of fuel needed. So here we have basically the same DEVICE as in a _______________ power station where you BURN ______ or gas, but the material is more _____________. At the same time, it can be built well outside the town, it can be built where it isn't going to do any harm to local population. ACTIVITIES 1. Put these words in the corresponding hole in the text: fuel,
rods,
reaction,
reactor,
uranium,
complicated
core,
amounts,
coal,
drives
heat,
moderator,
tonnes,
dangerous,
nuclear,
conventional,
by-products
2. Look in the text a synonym of these words, among the words in bold type: very far from
while
very
seems
go on with
non-nuclear
ways
stop
kept
secondary product
different from
quantity
existing
plant
move
moderately
3. Explain in english the meaning of the words in CAPITAL LETTERS 4. Separate into two different words the contracted words that appear in the text. 5. Listen to the oral exposition in https://www.youtube.com/watch?v=H3IHWvIGVjg
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Hydroelectricity 1.- Complete the text with the missing words, while listening (twice) the video called “How hydroelectricity works”. (http://www.youtube.com/watch?v=rnPEtwQtmGQ) MISSING WORDS IN ALFABETICAL ORDER: coils copper dam drives drop falling flow flows generator intake large level lines magnets pipe power pressure renewable river rotor spins stations turbine voltage water waterfall (NUMBER) ___________ cubic meters of water flow past here every minute at almost (NUMBER) ___________ kilometers per hour. That’s enough water to fill about (NUMBER) ___________ Olympic swimming pools every day. Standing here, you can actually feel the ___________ of the water. Harnessing that power is what hydroelectric ___________ have been designed to do for over a (NUMBER) ___________ years in Ontario. In essence, they are the factories that convert the energy of ___________ water into the ___________ of electrons, or what is commonly called electricity: the electricity that powers the province. Most hydroelectric stations use either water diverted around the natural ___________ of the river, such as a ___________ or rapids, or a ___________ is built across the river to raise the water level and provide the drop needed to create a driving force. Water at the higher ___________ is collected in the fore-bay. It ___________ through the plant ___________ into a ___________ called the penstock, which carries it down to a ___________ water wheel at the lower water level. The water ___________ increases as it flows down the penstock. It is this pressure and flow that ___________ the turbine that is connected to the ___________. Inside the generator is the rotor that is spun by the turbine. ___________ electromagnets are attached to the ___________, located within coils of ___________ wire called a stator. As the generator rotor ___________ the___________ a flow of electrons is created in the ___________ of the stator. This produces electricity that can be stepped up in ___________ through the station transformers and sent across transmission ___________. The falling ___________, having served its purpose, exits the generating station to the tailrace where it rejoins the mainstream of the ___________to continue the
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cycle of creating clean, ___________energy for Ontario. 2.- Listen again to it and try to complete the NUMBERS that appear. 3.- Finally, read the text aloud. 4.- Put in the boxes the following words: TURBINE,
GENERATOR,
RIVER,
INTAKE,
RESERVOIR,
POWER LINES.
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UNIT 3 HEAT VOCABULARY •
temperature [temptra]15
•
change (verb & noun)
•
increase (verb & noun)
•
thermometer
•
degree
•
high (adj.) ↔ low
•
above zero ↔ below zero
•
rise (verb, intransitive) (past. rose, p.p. risen [rizn])
•
↔ fall (verb, intransitive) (past. fell, p.p. fallen)
•
raise (verb, transitive) (past & p.p. raised)
•
particle
•
bond
•
vibrate (verb) [vaibreit] → vibration
•
collide (verb) → collision
•
transfer (verb) (past & p.p. transferred) → transference
•
measure (verb &noun) [me∫or]
•
unit
•
heat (verb & noun) [hi:t]→ hot (adj.) ≠ hit [het]
•
cool (verb & noun)
•
warm (adj. & verb)
•
gain (verb) ↔ lose (past & p.p. lost)
•
mass → kilogram
•
need (verb & noun)
•
amount ≈ quantity
15 When not indicated, it is a noun. Or the same category as the precedent word.
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•
melt (verb) (past & p.p. melted) ↔ freeze (past froze, p.p. frozen)
•
boil (verb)
•
solid, liquid and gas
•
insulate (verb) → insulation
•
conduct (verb) → conduction
•
dense (adj.) → density
•
emit (verb) ↔ absorb ↔ reflect
•
emission ↔ absorption ↔ reflection
•
wave
•
through (prep.)
•
vacuum
•
dark (adj.) ↔ bright
•
inside (adv.) ↔ outside
•
install
•
foam
•
wool
•
foil → For example, aluminium foil
•
draught
•
save (verb) → savings
•
cost (verb & noun)
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THE EFFECTS OF HEATING Temperature is a measure of how hot an object is. We use a thermometer to know the temperature of an object. The thermometer is divided into degrees, but it can use several scales. The most common scale measures temperature in degrees Celsius (ºC). On this scale 0ºC is defined as the temperature at which pure ice melts – but temperatures can be much lower than this. Different temperatures can be shown on a thermogram – each colour represents a different temperature. The degree Celsius (°C) scale was created by dividing the range of temperature between the freezing and boiling temperatures of pure water into 100 equal parts. Thus the boiling temperature of water is 100 ºC. If an object is cooled until all the particles stop moving then they cannot lose any more kinetic energy. That is the lowest possible temperature that can be reached and it is called absolute zero. This means a complete absence of heat. The Kelvin (K) scale is used by the scientists all over the world to measure the temperature. If you want to convert Celsius degrees to Kelvin scale, you just have to add 273. Kelvin (K) = degrees Celsius (ºC) + 273 In US they still use the Fahrenheit scale. To convert from Fahrenheit to Celsius and vice versa you would use the following: degree F = degree C x 1.8 + 32 degree C = (degree F - 32) / 1.8 Specific heat capacity If the temperature of a solid, liquid or gas changes, then it has gained, or lost, energy, called heat. The amount of energy depends on: •
the temperature change
•
the mass of the object
•
the material the object is made from
The specific16 heat capacity of a material is a measure of the energy of the material. It is different for different materials and tells us how much energy (in 16 'specific' means 'for each kilogram'
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Joules) you need to raise the temperature of one kilogram of the material by one degree Celsius. Don't confuse temperatures with temperature changes. If the temperature changes to 1ºC it is just above the freezing point of water – this is not the same as by 1ºC, that means 'one degree more than it already has'. Energy (heat) = mass x specific heat capacity x temperature change17 Q = m c Δt Specific heat capacity is measured in J/kg ºC. For example, the specific heat capacity of water is 4 180 J/kg ºC, which means that you need 4180 joules to heat 1 kg of pure water by 1 ºC. One century ago, heat used to be measured in calories. This is the amount of heat needed to raise the temperature of 1 gram of pure water by one degree Celsius. This means that the specific heat of water is 1 cal/g ºC. The equivalence between calories and jules is: 1 calorie = 4.18 J AN EXAMPLE OF A PROBLEM Calculate the energy in joules and calories required to heat 6.25 grams of water H 2O from 5.5ºC to 70.8ºC Q = m c delta t delta t = t final – t initial = 70.8 - 5.5 = 65.3 ºC m = mass in grams = 6.25 g c = specific heat = 4.18 J / g ºC for water Putting all the datas in the equation above, you can find the Q (i.e. energy) in joules. Then to convert to calories from joules 1 calorie = 4.18 joules So, lets say you got y joules above so, y joules x 1 calories / 4.18 joules = ? calories
Latent heat Heating an object raises its temperature except at the melting point and boiling point. At these temperatures, the energy is being used to change the state, from solid to liquid, or liquid to gas. Because the temperature does not change, the heat given to the substance is called latent18 heat. Solid objects are held together by forces between the particles (atoms or molecules), and have a regular shape. The particles vibrate more as the object is heated. Liquid particles have enough energy to break the inter-molecular bonds and slide over each other. At the melting point, heating the solid does no 17 'change' is usually represented in Physics by the greek letter 'delta' Δ 18 'latent' means 'hidden'
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increase the vibrations, but gives the particles enough energy to break the bonds. When a liquid freezes, it looses this energy to its surroundings. Gas particles have enough energy to separate completely. At the boiling point, heating the liquid breaks the inter-molecular bonds completely and the particles form a gas.
A sketch of particles must show that the particle size doesn't change. Solid particles are regularly spaced and touching. The liquid particles are still touching – there a no gaps large enough for another particle to fit in. Gas particles are very widely spaced, so do not draw too many. •
Watch it live in http://www.harcourtschool.com/activity/states_of_matter/
•
Here you have more examples:
http://www.nyu.edu/pages/mathmol/textbook/statesofmatter.html There is a small increase in potentianl energy (separation) of the particles when an object changes from solid to liquid and a bigger increase when a liquid changes to gas. The specific latent heat of melting of a material is the energy in joules needed to melt 1 kg of the material without changing its temperature. The specific latent heat of freezing is the same as that for melting, but the energy is given out by the material, instead of by its surroundings. The specific latent heat of boiling of a material is the energy in joules needed to boil 1 kg of the material without changing its temperature. Specific latent heats are measured in J/kg. Energy needed to change state = specific latent heat x mass
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HEAT TRANSFER Objects that are hotter than their surroundings cool down, objects that are colder than the surroundings heat up. The bigger the temperature difference between an object and its surroundings, the faster this happens. Heat by conduction In a hot solid, the atoms vibrate more than in a cold one. They collide with atoms next to them and set them vibrating more. The kinetic energy is transferred from atom to atom. Metals are the best conductors, followed by other solids. Liquids are generally poor conductors. Gases are very poor conductors. Poor conductors are called insulators. Metals are good conductors because they have 'free' electrons that transport energy from the hot to the cold end of the material much faster. Heat transfer by convection In a hot fluid (gas or liquid), the atoms have more kinetic energy than in a cold fluid, so they move more. They spread out and the fluid becomes less dense. The hot fluid rises above the denser cold fluid forming a convection current.
Remember: hot gases and liquids rise, not 'heat' Heat transfer by radiation All objects emit (give out) and absorb (take in) thermal (infra-red) radiation. Some objects also reflect radiation. This radiation transfers energy in the form of infra-red electromagnetic waves. The hotter the body is, the more energy it radiates. Radiation will travel through a vacuum â&#x20AC;&#x201C; it does not need a medium (material) to pass through. Dark and matt surfaces are good absorbers of radiation. Light and shiny surfaces are poor absorbers of radiation. Insulating homes In the winter we keep our homes much warmer than the outside temperature. This means that heat will be lost to the outside. If we reduce the heat lost, we 2nd ESO SCIENCE â&#x20AC;&#x201C; professor notes
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use less fuel and it costs less. We can do this by insulating our homes. •
Still air is a very good insulator. Some houses have cavity walls. The air gap between the two walls stops conduction. But air transfers heat if convection currents are set up. It is important to keep the air still. This can be done by cavity wall insulation -filling the cavity with a material containing trapped air, for example, foam or mineral wool.
•
A lot of energy is lost through the roof, because convection currents are set up. Loft19 insulation uses fibreglass or mineral wool to keep the floor of the loft from getting hot.
•
Reflective foil on walls reflects infra-red radiation.
•
Draught-proofing stops the hot air leaving and cold air entering the house.
All these improvements cost money to buy and install, but they save money on fuel cost. You can work out the payback time, which is the time it takes before the money spent on improvements is balanced by the fuel savings, and you begin to save money. Cost of insulation Payback time in years = --------------------------------------cost of fuel saved each year If the prize of the fuel increases, the payback time will be less.
19 The upper room of a house, just under the roof.
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Geothermal energy process 1.- Put these fragments of sentences in the same order that appear in the following video: (http://www.youtube.com/watch?v=rfUQy86ZMpQ) First, read the sentences aloud. Then watch the video, say “stop!” if you recognize one, and put a number next to it. (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k) (l)
is heated to high temperatures by magma renewable energy source the voltage is increased the hot fluid and steam move through a surface pipeline steady supply of electrical power create low pressure steam the fluid flows through these wells toward the surface is sent to a turbine most of the fluid vaporizes shaft connected to an electrical generator return to the underground reservoir the steam spins the turbine’s blades
2.- Find in the previous sentences the underlined words that match with these definitions: A) B) C) D) E) F) G) H) I) J) K)
regular and continuous hot fluid material inside the earth hole into the ground to obtain water, petroleum or gas long tube to convey water, oil or gas substance (gas or liquid) that has no fixed shape force exerted to a surface machine in which a wheel is turned by the force of water or steam one of the flat parts of a fan (or other similar objects) that goes round become bigger natural or artificial lake, even underground origin of something, for example, a fountain of water.
3.- Explain, in three or four lines, how can you make electricity with geothermal energy.
Geothermal heating 1.- Watch this video and take note of the words that you understand:
(http://www.youtube.com/watch?v=-ajqiPe_9Ko&NR=1) 2.- True or false? If it is false, change a word to make it true: (a) (b) (c) (d) (e) (f) (g) (h) (i)
In countries like Canada, seabirds come and go. In the summer months, it can be quite cold. Temperature of the surface of the earth changes with the seasons. About two meters under the ground it is about fifty degrees Celsius. A large hole is made in the ground and filled with serious pipes. In the winter, hit from the ground is absorbed and pushed upwards. In the summer, heat from the house is absorbed and pushed upwards. One of the benefits of geothermal heating is that you can waste a lot of money. Geothermal heating uses no fossil bills like oil or gas.
3.- Explain, in two or three lines, if you would like to install geothermal heating in your future house, and why.
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How air conditioning works (http://www.youtube.com/watch?v=1MiQCBIx1mM&NR=1&feature=fvwp) 1. Fill up the sentences using one of the words of each pair. (a) If you live in a ______ part of the country...
hot / heat It’s probably hard to imagine surviving _________ an air conditioner.
(b) with /without (c) ...you have a big ______ like this in the backyard. box / fox (d) Have you ever _____________ what’s it doing back here? wonder/ wondered (e) The basic idea behind any air conditioner is __________. evaporation / vaporization (f) When a liquid evaporates it feels _______. coal / cool (g) If you put alcohol on your ______... skull / skin (h) ...you can _____ the coolness as it evaporates. file / feel (i) An air conditioner __________ a liquid complains / contains (j) The __________ evaporates inside the house. squid / liquid (k) It evaporates inside a set of metal ________... cables / coils (l) ...and the liquid _______ the coils extremely cold. shakes / makes (m) A _______ blows air across the coils... fan / funny (n) When it evaporates, the liquid ________ into a gas. burns / turns (o) To turn that gas back into a liquid, you use a ___________. pressure / compressor (p) ... but it gets really ______ in the process. hole / hot (q) It’s a continuous _________ … cycle / bicycle (r) ...your house is _______ cooled the entire time. getting / heating 2. Match each word with its opposite: A) surviving 1. dying B) backyard C) evaporation
2. front garden 3. condensation
D) hard E) behind
4. easy 5. in front of
F) coolness G) inside
6. heat 7. outside
H) extremely I) entire
8. moderately 9. partial
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How to insulate your home Watch this video (http://www.youtube.com/watch?v=CptXMyz5PG4) and match the two halves of the paragraphs. The sentences at the left are in the same order as in the video. 1) Shockingly around half of all of your heat can escape if your home isn’t properly1 insulated. So instead of turning that thermostat up, get insulating, and we friendly people at Home Serve are going to show you how. 2) Doors. Do you ever notice it gets a little chillier2 near doors? This is because the warm air is escaping and cold air is creeping in. Fit draft excluders around all exterior doors and interior if needs be. 3) Windows. Cracks and crevices around window frames3 are also a popular escape point for warm air. To check for weak points run the palm of your hand around the edge of the frame. If you feel a breeze, you’ve got a hole. Patch these up with a putty or sealer. To make it really easy on yourself, get the type that comes in a tube. Squirt it on, smooth it over, job done. 4) Floors. Most homes have gaps4 between the skirting board and the floor. And if you have floor boards there’s likely to be a few gaps between them too. This is another job for our trusty silicon sealer. 5) Lofts. Laying loft5 insulation on the average home can save 6) Pipes and Hot Water. Wrapping6 your hot water tank in a cozy 80 milimeter jacket will cut heat costs by 75% and you will recoup the cost of it in less than six months. 7) There you have it. A little work and cash up front will save you and the planet a hell of a lot more in the long run7.
A) If you have a wood floor and want to go the whole hog, you can get the experts in to fit floor insulation beneath8 the boards. Putting a rug9 down isn’t a bad idea either. B) This will save you hundreds on your energy bills as well as making a massive reduction to your carbon footprint10. Everyone’s a winner. C) Get those pipes insulated too. D) Sealant strips can be bought cheaply from DIY stores and are dead easy to fit, just like applying sticky tape11. Don’t forget to get a brush trim for letter boxes and the bigger gaps and the bottom of doors. E) It’s worth investing in double glazing12 if you don’t already have it. This could save you lots of money on your annual heating bill. Closing curtains or blinds 13 after dark also traps14 in the warm air and prevents drafts and it looks cozier too. F) a whopping 1 ton dioxide a year and make a major dent in your bills. G) Now sit back and enjoy your energy improved home.
Match the English words marked with little numbers with its meaning in Spanish. Use your deduction, not the dictionary! a. acristalamiento
h. huella
b. adecuadamente
i. envolver
c. alfombra
j. marcos
d. ático
k. más frío
e. atrapa
l. persiana
f. cinta
m. plazo
g. huecos
n. por debajo
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UNIT 4 WAVES VOCABULARY •
vibration
•
transmit (verb)
•
through (prep.) [zru]
•
right angle
•
peak
•
trough [traf]
•
displacement
•
between (prep.)
•
neighbour
•
speed → fast (adj.)
•
increase (verb) ↔ decrease
•
compressions ↔ rarefactions
•
squash (verb) ↔ stretch
•
earthquake
•
stress
•
record (verb & noun) [record = noun / ricord = verb]
•
surface
•
shadow
•
reflect (verb) → reflection
•
deep (adj.) → depth
•
boundary
•
vacuum
•
hit (verb) [past hit, p.p. hit]
•
behave (verb) → behaviour
•
mirror
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•
lens
•
rainbow
•
bend (noun & verb) [past bent, p.p. bent]
•
spread (verb) [past spread, p.p. spread]
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DESCRIBING WAVES A wave is a vibration or disturbance which is transmitted through a material – called medium – or through space. Waves transfer energy and can also be used to transfer information from one place to another, but they do not transfer material.
Transverse waves A transverse wave has the vibrations at right angles (perpendicular) to the direction of wave travel. The wave has peaks (or crests) and troughs20, as shown in the diagram. The amplitude is the maximum displacement (change in position) from the undisturbed position. The wavelenght (symbol λ) is the distance between two neighbouring peaks or troughs.
A common mistake is to mark the amplitude from the top of a peak to the bottom of a trough – this is actually twice the amplitude The frequency is the number of complete waves that pass through a point in one second. It depends on how fast the source of the waves is vibrating. The frequency is measured in hertz (Hz) where one hertz is one cycle (wave) per second. The wave speed depends on the medium that the wave is travelling through. As the frequency increases the wave speed does not change, but the wavelength will decrease. This is shown in the next figure.
20 Trough [traf] is also the place where you put food or water for domesticated animals.
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The wave equation relates the wavelength and frequency to the wave speed. The wave equation, for all waves: wave speed = frequency x wavelength v=f·λ If f is in Hz (hertz) and λ is in m (meters), then v is in m/s (meters per second) Examples of transverse waves are: water waves, light electromagnetic waves, and the seismic waves called S-waves.
and
other
Longitudinal waves A longitudinal wave has the vibrations parallel to (along the same direction as) the direction of the wave travel. As shown in the diagram, the wave has compressions (or squashed parts) and between these are stretched parts called rarefactions.
One wavelength is the length of one complete wave – a compression and a rarefaction. Longitudinal waves show the same behaviour (for example reflection and refraction) as transverse waves.
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SEISMIC WAVES Most earthquakes occur along plate boundaries when rocks that are stressed suddenly break. Like ripples from a pebble tossed into a pond, shock waves radiate from the rupture in all directions. These seismic waves shake Earth’s surface and race through its interior. There are two types of shock waves called seismic waves that travel through the Earth (other types travel over the surface). These are called P-waves (primary waves) and S-waves (secondary waves). They can be caused by an earthquake, or a large explosion, and are detected at monitoring stations around the Earth by instruments called seismometers. Next figure shows a seismograph – a record of the waves received at a monitoring station.
P-waves are longitudinal waves that travel through solid and liquid rock. They travel faster through the Earth and other seismic waves so they are the first to be detected after an earthquake. S-waves are transverse waves and can only travel through the solid materials in the Earth. They are detected after primary waves because they have a lower speed. Transverse waves can travel on the surface of liquids – but not through them.
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Figure below shows the paths of P-waves and S-waves through the Earth following an earthquake. The point on the Earth's surface directly above the earthquake is called epicentre. On the opposite side of the Earth to the epicentre no S-waves are detected. This tells us that there must be a part of the Earth that is liquid and only Pwaves pass through it. This is how we know there is a liquid outer core.
The S-waves form a shadow region on the opposite side of the Earth to an Earthquake. This shows that part of the Earth's core is liquid. We can investigate the structure of the Earth's crust by setting up monitoring equipment at different points and setting off a controlled explosion. We record the waves arriving at the monitoring points. The time after the explosion that waves take to arrive depends on the speed of the waves (which in turn depends on the medium they pass through) and whether they have been reflected at a boundary between different materials. Analysing this data gives us information about the structure of the rocks. â&#x20AC;˘
LABELLING GAME (Layers of the Earth) http://www.missmaggie.org/scholastic/science_eng_launcher.html
How do we determine an earthquake's size? Each year, about 800,000 earthquakes are recorded worldwide. Most are too small to be felt, but typically at least one is a great earthquake. We measure the energy that each earthquake releases. The Richter Scale, one of several in use, ranks an earthquake's magnitude based on seismic wave amplitude at a standard distance. With each step up the scale, the amplitude increases 10-fold and the energy released increases 30-fold.
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PLATE TECTONICS AND VOLCANOS Explore the following website: http://www.mnh.si.edu/earth/main_frames.html You can choose between multimedia version or printable version. In any case, click on Plate tectonics and volcanoes. Volcanoes slide show: http://msnucleus.org/membership/slideshows/volcano.html Everything you have to know about volcanoes.
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Sound and ultrasound Sound waves are longitudinal waves. They pass through solids, liquids and gases. Ultrasound waves are sound waves with a frequency that is too high for humans to hear. Like all waves, sound waves and ultrasound waves can be reflected – the reflection are called echoes. Echoes can be used for measuring distances. Figure shows how the depth of water can be measured by reflecting an ultrasound pulse off the seabed. Echo sounding works like this: •
An ultrasound pulse is emitted from a vibrating crystal.
•
The same crystal detects the reflected pulse.
•
The time for the pulse to travel from the crystal to the seabed and back to the crystal is recorded.
•
The distance can be worked out using the equation: speed = distance / time distance = speed x time
The speed of the ultrasound waves in water is known. The depth is half the distance the wave travelled, so: depth = speed x time / 2 Ultrasound is also used to scan parts of the body, like the eye or an unborn foetus. This works because part of the pulse is reflected at each boundary between different tissues (for example skin and bone). The reflections from the tissue boundaries are all used to build up a picture. Ultrasound is much safer than X-rays because it does not damage body cells or DNA and does not cause mutations.
Electromagnetic waves Electromagnetic waves are transverse waves, which are made up of vibrating magnetic and electric fields. They can travel through a vacuum and all travel through space at a speed of 300 000 km/s. The different types of electromagnetic waves form the electromagnetic spectrum, shown in the next figure.
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WAVE BEHAVIOUR When waves encounter new mediums, barriers, or other waves they can behave in different ways. In physics these behaviours are described using some of the terms below.
Reflection The word "reflection" is used in everyday life to describe what we see in a mirror or on the surface of the water. In physics, a reflection is when a wave encounters a new medium that acts as a barrier, causing the wave to return to the original medium. The wave "reflects" off the barrier at an angle that is equal to the angle of the wave hitting the barrier (see below).
Refraction Refraction of a wave occurs when a wave changes direction upon moving from one medium to another. Along with the change of direction, refraction also causes a change in the wavelength and the speed of the wave. The amount of change in the wave due to refraction is dependent on the refractive index of the mediums.
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One example of refraction is a prism. When white light enters the prism, the different wavelengths of light are refracted. The different wavelengths of light are each refracted differently and the light is split into a spectrum of colors. That is the explanation of the rainbow, for example.
Types of Lenses There are different ways to classify lenses. One way to classify lenses is by how they bend light. Converging A converging lens will cause the light rays to bend to a specific focal point. Another name for this type of lens is a positive lens.
Diverging A diverging lens will cause light rays from a specific focal point to be spread out. Another name for this type of lens is a negative lens.
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Absorption Absorption is when a wave comes into contact with a medium and causes the medium's molecules to vibrate and move. This vibration absorbs or takes some of the energy away from the wave and less of the energy is reflected. One example of absorption is black pavement which absorbs energy from light. The black pavement becomes hot from absorbing the light waves and little of the light is reflected making the pavement appear black. A white stripe painted on the pavement will reflect more of the light and absorb less. As a result the white stripe will be less hot.
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LISTENING COMPREHENSION
LOUDNESS, PITCH AND QUALITY https://www.youtube.com/watch?v=dbeK1fg1Rew
Fill in this transcription of the video with the words that you have at the end. We can record _________ variations and sound waves with this kind of instrument - an oscilograph. Sound waves are striking the diaphragm of the left. The stylist records the sound waves as a graph. Later we shall use such graphs to represent sound _______. Compressions cause the stylist to move __________, while rarefactions cause it to move downward. So far we've seen how sound waves are produced. Next, we'll identify 3 auditory __________ of musical sounds: loudness, pitch, and quality. We begin with ____________. Every sound sets off a disturbance of a transmitting medium. The larger the disturbance or displacement of the individual particles, the greater is the height of its graph above the neutral line. This displacement above the neutral line is called ____________. And it is amplitude that determines loudness. As the amplitude gets bigger, loudness increases. Next let us consider pitch, the auditory effect of ____________. First we hear the sound of Middle C. Next we hear G below Middle C. And now the sound of C below Middle C. What causes such differences in _______? To explain such differences, we picture two different sound waves. Here the lower fork makes more complete _____________ per second. Therefore, it's frequency is greater. It is evident that the one with the greater ___________ has the higher pitch.
Words:
effects amplitude pitch vibrations frequency (2) upward pressure loudness
waves
READING COMPREHENSION Kids Be Gone: High Pitch Only Teens Can Hear Used As Deterrent The sound is coming from a wall-mounted box, but not everyone can hear it. The device, called the Mosquito, (1) and is installed outside the building. The gadget (2) in the United States last year. Almost 1,000 units have been sold in the U.S. and Canada. To Eddie, it's tormenting. "It's horrible, loud and irritating," he said. "I have to hurry out of the building because (3)." The high-frequency sound can be heard by most people in their teens and early 20s who still (4). Whether you can hear the noise depends on how much your hearing has deteriorated -how loud you blast your iPod, for example. Civil liberties groups in England, Australia and Scotland (5) that infringes on the basic rights of young people. The noise can be heard by animals and babies, but is bothersome only to children older than 12 and becomes unbearable after several minutes, making it a perfect teen-repellent. The same sound (5) meant to fall on the deaf ears of adults, and is a popular download on the Internet.
Read the text. There are some gaps marked with numbers. Put these groups of words in the place where they make sense: (a) have sensitive hair cells in their inner ears
(b) describe it as a weapon
(c) is also used as a cell phone ring tone
(d) is audible only to teens and young adults
(e) made its debut
(f) it's so annoying
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LIGHT AND COLOURS https://www.youtube.com/watch?v=2ZsJpcOIiSU
Watch the video and match the two parts of the sentences: 1. 2. 3. 4. 5. 6. 7. 8. 9.
White light is actually... You can see the colors of light... The prism uses refraction... When you put all the colors together... If there isn't any light... The colors you see with your eyes... The colors that are not reflected... If you are looking to a yellow flower... When you use red light...
(a) ...are actually absorbed. (b) ...by using a prism. (c) ...all the colors except yellow are absorbed. (d) ...to separate light into several colors. (e) ...a combination of all colors of light (f) ...everything appears black. (g) ...they make white light. (h) ...everything appears red or black. (i) ...are only the colors that are reflected.
PLAY WITH THE FACTS OF LIGHT AND SOUND http://www.engineeringinteract.org/interact.htm
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ELECTROMAGNETIC SPECTRUM SONG http://www.youtube.com/watch?v=bjOGNVH3D4Y 1.Put in order these radiations from longer to shorter wavelength: a.X-rays b.microwaves c.visible light d.infrared radiation e.ultraviolet radiation f.gamma rays g.radio waves 1.Match these sentences with the radiations mentioned in exercise #1 a.It transmits the order from the remote control to the television. _____________________ b.They are used to see the bones and hidden bombs. _____________________ c.They heat food. _____________________ d.They are the most dangerous. _____________________ e.It kills bacteria and viruses. _____________________ f.It produces heat to treat some illnesses. _____________________ g.They transmit the signal from the TV station to your television. _____________________ h.It contains all the colors. _____________________ i.It produces the suntan on your skin. _____________________ j.It allows pictures to be taken in the dark. _____________________ k.They are used to kill cancer cells and sterilize. _____________________ l.It is used to detect false bank notes. _____________________ m.It is the only part of the spectrum that can be seen. _____________________
SCIENCE PLEASE
The Wonderful World of Colour https://www.youtube.com/watch?v=EHMH0uQDEOU&list=PL054EE2D3983CE1AE Fill the gaps with the given words: light
brain
wavelength
yellow
red
absorbs
reflects
colour
There's no such thing as colour. We live in a colourless world. Ahhh - colour is an effect produced in our eyes and _________ by light. White light consists of different lengths of ________ waves. Each wavelength produces a different ________ sensation. A banana looks _________ because its surface absorbs all ______________ except yellow, which it reflects back to our eyes. In the same way, a cherry looks ________ because its skin _________ all colours except red. And vanilla ice cream gives the illusion of being white because it __________ all wavelengths of light. So colour doesn't really exist, but it does have a very real effect on us.
ROY G BIV SONG https://www.youtube.com/watch?v=Gf33ueRXMzQ&list=PL054EE2D3983CE1AE Fill this introduction (Just before the song) with the following words: story – elf – father – song
In olden times, my ______ would help me remember the sequence of the color spectrum by telling me the ______ of a magical _____ named ROY G BIV. He even wrote a song about it. And the name of the _______ is Roy G Biv. Put in order these fragments of the song. Some of them are repeated several times!!! If that is the case, you repeat the number. (1) ROY G BIV is a colorful man and he proudly stands at the rainbow's end. (2) You'll never see ROY G BIV, but he's inside the rainbow. (3) "R" is for red, "O" is for orange, "Y" is for yellow, and "G" is for green. "B" is for blue, "I" for indigo, and "V" is for violet.
(4) ROY G BIV is a colorful man and his name spells out the whole color spectrum. (5) And inside every rainbow is the spectrum of light. (6) Because inside every rainbow, is the spectrum of light. (7) You'll never see a unicorn, but you'll see a rainbow. (8) And that spells ROY G BIV.
READING COMPREHENSION
Solar Energy The sun can be used as an energy resource without using generator. To collect the most energy from the Sun, the collector must track the path of the Sun. Some installations do this, but some are set at the best angle and collect fewer of the Sun's rays. There are three ways of using the Sun's energy: •
Passive solar heating for buildings. Glass is transparent to light and short wave infrared radiation, but reflects longer wave infrared radiation. When the Sun shines on glass windows the light and short wave infrared radiation will pass through and warm the objects inside. The warm objects emit longer-wave infrared radiation, but this cannot scape through the glass. This effect is called the greenhouse effect because it explains how plants are kept warm inside a glasshouse. The effect can be used in solar panels to warm water as shown in the figure. The water can be circulated in pipes around the house – the circulating water is often used to heat the water in the hot-water tank.
•
Solar furnace. Light and infrared radiation is reflected from shiny surfaces. A curved mirror - or a lot of them covering a big extension - can be used to focus all the Sun's rays to a point, where a high specific capacity fluid will be heated. This fluid is driven to a boiler, where steam is produced. Finally, this steam can be used to generate electricity, in the same way as other power stations work.
•
Solar cells. These are called also photocells or photovoltaic cells. They contain a crystal of silicon. Light falls on the crystal and gives energy to the electrons, so they are released. The electrons flow as a tiny electric current, suitable for a calculator, for instance. The current can be increased by increasing the surface area that the light falls on, or by increasing the light intensity. Solar cells are expensive to manufacture and are only about 30% efficient (although mew developments may increase this to 50%). This is why they are not yet in widespread use.
1. True or false? a. If the solar panel moves, it catches more Sun rays. b. Short wave infrared radiation cannot pass through glass. c. In a solar furnace, the heat of the Sun is stored in a liquid. d. In a photocell, the electrons are moved by the light. 2. Match these definitions with the underlined words. a. A closed vessel in which water is heated to provide steam: __________ b. A long tube used to convey water, gas, oil, etc: ___________ c. A device for converting mechanical energy into electrical energy: _______________ d. A flow of electrons through a conductor: ________________ e. A building with transparent walls and roof, used to cultivate plants: ________________ f. Radiant energy such as electromagnetic waves: ______________