Chapter 14: Energy: A Fuels Paradise

Chemistry for Changing Times 10th editionHill/Kolb

Daniel Fraser

University of Toledo, Toledo OH

©2004 Prentice Hall

Chapter 14 2

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 14 3

Units of Energy

• SI unit of power is Watt (W)

• 1 W = 1 J/s

Chapter 14 4

Types of Energy

• Potential energy: energy due to position or arrangement

• Kinetic energy: energy of motion

Chapter 14 5

Energy Transferred in Chemical Reactions

• Exothermic reactions: release heat to environment

• Endothermic reactions: gain heat from environment

Chapter 14 6

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 14 7

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 14 8

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 14 9

Fossil Fuels

• Coal, petroleum, and natural gas

• Produce ~90% of energy

• Release significant amounts of heat when burned

• Reduced forms of matter

Chapter 14 10

Rate of Usage of Fossil Fuels• Nonrenewable source of energy

• Using about 50,000 times faster than can be replenished

Chapter 14 11

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 14 12

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 14 13

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 14 14

Natural Gas

• Mostly methane, CH4

• Mostly used as fuel

• Used as raw material for industry– Used to make starting materials for plastics

• Rarest of the fossil fuels

Chapter 14 15

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 14 16

Crude Oil

• Crude oil separated in fractions based on boiling point of fraction

Chapter 14 17

Refining of Crude Oil

Chapter 14 18

Gasoline

• Mixture of C5H12 to C12H26 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 14 19

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 14 20

Electricity

• Most convenient form of energy

• Any fuel that can boil water can be used to produce electricity

Chapter 14 21

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 14 22

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 14 23

Nuclear Fusion• Process used by the sun

• Use 2H as fuel– Rare but have oceans of water to use

• Great technical difficulties have yet to be overcome

Chapter 14 24

Solar Heating

Chapter 14 25

Schematic Diagram of Solar Cell

Chapter 14 26

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 14 27

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 14 28

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 14 29

Fuel Cell• Fuel oxidized in an

electrochemical cell

• Requires fuel and oxygen be continuously provided

• Produces electricity– 40–55% chemical

energy converted

Chapter 14 30

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