Chapter 14: Energy: A Fuels Paradise Chemistry for Changing Times 10 th edition Hill/Kolb Daniel Fraser University of Toledo, Toledo OH ©2004 Prentice Hall

Chapter 142 Energy Ability to do work –Move car –Move electrons through copper wire Abundant energy is basis of modern civilization Convert raw materials to finished products

Chapter 143 Units of Energy SI unit of power is Watt (W) 1 W = 1 J/s

Chapter 144 Types of Energy Potential energy: energy due to position or arrangement Kinetic energy: energy of motion

Chapter 145 Energy Transferred in Chemical Reactions Exothermic reactions: release heat to environment Endothermic reactions: gain heat from environment

Chapter 146 First Law of Thermodynamics Also called law of conservation of energy Energy can be neither created or destroyed; it can only change forms Means: cannot have a machine produce more energy than it consumes –We can’t “win”

Chapter 147 Second Law of Thermodynamics Entropy: amount of disorder in a system Second Law states that entropy is always increasing –Universe becoming more disordered –Need energy to put things in order

Chapter 148 Early Fuels Human power Animal power –Domestication of horse and oxen Wood –Still used in many places as primary fuel Waterpower –Direct use good only for small scale factories

Chapter 149 Fossil Fuels Coal, petroleum, and natural gas Produce ~90% of energy Release significant amounts of heat when burned Reduced forms of matter

Chapter 1410 Rate of Usage of Fossil Fuels Nonrenewable source of energy Using about 50,000 times faster than can be replenished

Chapter 1411 Coal Complex combination of organic and inorganic materials –Formed from ancient plant material Quality of coal depends on carbon content Most plentiful fossil fuel

Chapter 1412 Coal Gasification and Liquefaction Convert coal to more usable forms Leaves behind most of the impurities Requires lots of energy and water Dispose of materials left over

Chapter 1413 Uses and Problems of Coal Very high energy released when burned Source of organic chemicals Coal mining is one of the most dangerous professions Source of pollution –Fly ash –American coal has high sulfur content –Need to clean it before burning

Chapter 1414 Natural Gas Mostly methane, CH 4 Mostly used as fuel Used as raw material for industry –Used to make starting materials for plastics Rarest of the fossil fuels

Chapter 1415 Petroleum Complicated mixture of liquid organic compounds –Mostly hydrocarbons –Probably produced from ancient animal material Used for fuel and raw material Source of most industrial chemicals

Chapter 1416 Crude Oil Crude oil separated in fractions based on boiling point of fraction

Chapter 1417 Refining of Crude Oil

Chapter 1418 Gasoline Mixture of C 5 H 12 to C 12 H 26 hydrocarbons Some of these hydrocarbons are better fuels –The more branched, the better Octane rating –Isooctane assigned value = 100 –Heptane assigned value = 0 Octane rating = 90 means the same as having 90% isooctane and 10% heptane

Chapter 1419 Gasoline Additives Used to improve octane rating Tetraethyl lead is most effective –Lead contributes to learning disabilities in children Methyl tert-butyl ether (MTBE) – –Improves octane rating –Lowers CO emission –Toxic if it gets into groundwater Ethanol –Produced by fermentation of corn –Favored in farm regions

Chapter 1420 Electricity Most convenient form of energy Any fuel that can boil water can be used to produce electricity

Chapter 1421 Nuclear Energy Nuclear reactors use nuclear fission –Heat released is used to boil water Widely used –France gets >75% of electricity from nuclear energy Does not use fossil fuels No air pollution

Chapter 1422 Nuclear Problems Must shield workers from radioactivity Prevent contamination if a problem arises Disposal of wastes –Some waste products have half-lives of thousands of years –Hard to build site that lasts that long

Chapter 1423 Nuclear Fusion Process used by the sun Use 2 H as fuel –Rare but have oceans of water to use Great technical difficulties have yet to be overcome

Chapter 1424 Solar Heating

Chapter 1425 Schematic Diagram of Solar Cell

Chapter 1426 Uses of Solar Energy Only about 10% of sunlight is converted to electricity Solar cells tend to be expensive –Price is coming down What do you do on cloudy days?

Chapter 1427 Biomass Use plant material as energy source Can use directly –Burn material Can convert to another form –Make alcohol from grains –Produce methane from breakdown of plant material Not very efficient way to produce energy

Chapter 1428 Hydrogen Burns very cleanly Chemically tied up in other compounds –Requires energy to separate from water Hard to store May be used in fuel cells

Chapter 1429 Fuel Cell Fuel oxidized in an electrochemical cell Requires fuel and oxygen be continuously provided Produces electricity –40–55% chemical energy converted

Chapter 1430 Wind and Water Power Wind power uses moving air to turn turbines –Clean, free, and abundant –What do you do when wind stops blowing Water Power –Store behind large dams –Use moving water to turn turbines