UNIT 2

UNIT 2Energy

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What is energy?Energy is the ability of a system to do a work. Its a physical quantity which produces a change or an effect.The unit International System, the unit of measurement for energy is the joule (J). There are other units:

1kJ = 1.000 J1 Cal = 4,18 J1kCal = 1.000 Cal = 4186 J1 kWh = 3.600.000 J = 860 kCal

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Properties of energyEnergy cant be created or destroyed. The law of conservation of energy: the total energy of an insolated system remains constant, its conserved over time.Energy can be transformed from one form to another. For example, chemical energy from fuel is transformed into mechanical energy in cars.Energy can be transferred from one body to another. For example, when we hit a ball with racket, most of the mechanical energy in the racket is transferred to the ball.Energy can be stored. For example, batteries store chemical energy.Energy can be transported form one place to another. For example, electrical energy is transported through electric cables.

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Forms of energy (I)Chemical energy. This is stored energy contained in chemical compounds (atoms and molecules). It is released during chemical reactions. Electrical energy. This is the energy produced by the flow of electric charge: matter is made up of atoms where there are some even small particles called electrons that are constantly moving. Their movement depends on how much energy is has. Humans can force these moving electrons along a path from one place to another. We generate electrical energy when we move these electrons from one atom to other, with the use of magnetic forces.Thermal energy. Its released as heat. Matter is made up of particles or molecules that move (or vibrate) constantly. A rise in the temperature of matter makes the particles vibrate faster. The hotter the substance, the more its molecules vibrate, and the therefore the higher its thermal energy.Secundaria Digital

Forms of energy (II)Electromagnetic energy. Its stored in electromagnetic waves, that can travel through vacuum. There are different kinds of waves and all of them have different wavelenghts, properties and power, and all interact with matter differently (changing its properties). From less dangerous to more dangerous, they are: radio waves, micro waves, infrared waves, visible light, UV waves, X waves and Gamma waves.Mechanical energy. Its the sum of:

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Forms of energy (III)Nuclear energy. Its stored in the nuclei of atoms.

Nuclear fission. In this process, the nucleus of an atom splits into two or more parts, releasing a vast amount of energy. The two smaller atoms dont need as much energy to hold them together as the longer atom, so the extra energy is released as heat and radiation.Nuclear fusion. In this process, the nucleus of an atom joins to other nuclei to for a heavier atom. A vast amount of energy is also produced.

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Energy resourcesNon-renewable energy resources: are limited energy resources obtained from the Earths crust that have formed in the Earth hundreds of millions of years. They are fossil fuels (coal, crude oil nad natural gas) and uranium (nuclear fuel). Once consumed they cant be replaced.Renewable energy resources: energy resources which are replenished continuosly and will not run out. Renewable energy includes biomass, wind, hydro-power, geotermal, tidals and solar sources.Secundaria Digital

Cmo se genera le energa?(en espaol)

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Non-renewabble energy resources: advantages, disadvantages and uses (I)TYPEADVANTAGESDISAVANTAGESUSESCOALEasy to transport.CheapLarge reserves.Underground coal mining is dangerous.CombustionDamage to the environment.EnergyHeatProduce steel.

PRETOLEUMMore efficient than coal.Easy transportation.Produces rain and global warming.High priceAgriculture, plastics, tires, pharmaceuticals, dyes, detergents, and other.

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Non-renewabble energy resources: advantages, disadvantages and uses (II)TYPEADVANTAGESDISAVANTAGESUSESNATURAL GASLess harmful than coal and oil.Easy transportAbundantCheaper than electricityToxic and flammableComplex processingExpensive installationElectricityHeatingURANIUMIt produces a lot of energy.No pollutionIt produces radioactive waste.LimitedAn accident can release dangerous substances.ElectricityHeatAs weapon

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Renewabble energy resources: advantages, disadvantages and uses (II)TYPEADVANTAGESDISAVANTAGESUSESBIOMASSIt produces little wastes, which also are biodegradable.Less contaminating than fossil fuels.Most of it are wastes of human activities.Low energetic performanceBig volumen in fresh state. ElectricityDirect combustionCharcoal and liquid and gaseous fuels production

HYDROLow perfomanceCheapIt doesnt produce waste or contaminatingsIt helps to control floodsExpensive transportIt depends of the weatherIt produces big alterations in the environment.Dangerous because of dam breakingElectricityDistribute water

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Renewabble energy resources: advantages, disadvantages and uses (II)TYPEADVANTAGESDISAVANTAGESUSESSOLARCleanCheapIt depends of the weatherIt cant be storagedIt requires much terrain.ElectricityHeat wter

WINDLow costHigh perfomanceIt depends of the weatherHard storageDangerous for birdsIt requires much terrain.Landscape alterationsInterference in radio, tv, radars.Electricity

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Non-renewabble energy resources: advantages, disadvantages and uses (II)TYPEADVANTAGESDISAVANTAGESUSESTIDALCleanNo wastesEcosystem alterationsLimited to zones with perfect conditionsLow energetic performanceExpensiveElectricityGEOTHERMALNo wastesHard and expensive localizationElectricityHeating

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