Chemistry for Changing Times
12th Edition
Hill and Kolb
Chapter 15
Energy:
A Fuels Paradise
John Singer
Jackson Community College, Jackson, MI
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Energy
Most of all of the energy on planet Earth comes
to us from the sun.
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Energy
Energy is defined as the ability to do work or
transfer heat.
The SI unit of energy is the joule (J).
(1 J = 0.2388 cal)
The SI unit of power is the watt (W).
(1 W = 1 J/s)
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Energy
Energy can be considered to exist in two
forms:
1. Potential energy: Energy of position or
stored energy.
2. Kinetic energy: Energy of motion.
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Energy
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Energy and the Life Support
System
The biosphere is the thin film of air, water, and
soil where life exists. Only a small amount of the
energy the biosphere receives is used to support
life.
30% of solar radiation is reflected back to space.
23% of solar radiation powers the water cycle.
<0.02% is used by green plants to power
photosynthesis. Photosynthesis produces
oxygen and stores energy for all animals on the
planet.
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Energy and Chemical Reactions
Factors that affect the rate of a chemical
reaction include:
• Temperature: Increasing temperature
increases reaction rates.
• Concentration reactants: Reaction rates are
dependent on reactant concentration. As
concentration increases, rate increases.
• Presence of catalysts: Catalysts increase
the rate of reactions by lowering activation
energy.
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Energy and Chemical Reactions
Exothermic reactions release heat energy to the
surroundings.
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Energy and Chemical Reactions
Endothermic reactions absorb heat energy
from the surroundings.
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Energy and Chemical Reactions
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The First Law of
Thermodynamics
Energy can neither be created nor destroyed.
This is also known as the law of conservation
of energy.
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The Second Law of
Thermodynamics
Energy flows
spontaneously from
hotter objects
toward colder
objects.
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The Second Law of
Thermodynamics
Entropy is a measure of dispersal of energy.
Another way of stating the second law is to say
that for all spontaneous processes, the entropy
of the universe is increasing.
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People Power: Early Uses of
Energy
Early man obtained energy from hunting and
gathering of animals and plants.
Plant materials were the first fuels. Even today,
wood and dried dung are the principle fuel used
by one-third of the people on Earth.
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People Power: Early Uses of
Energy
Waterwheels and
windmills convert the
kinetic energy of
moving water and
wind into mechanical
energy.
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Fossil Fuels
Fossil fuels including coal, oil, and natural gas
provide more than 90% of the energy consumed
in a modern society.
Fuels are substances that, when burned,
release significant amounts of energy. Fuels are
a reduced form of matter. Combustion is an
oxidation process that is exothermic.
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Fossil Fuels
Fuels (reduced substances) vs. nonfuels
(oxidized substances)
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Reserves and Consumption
Rates of Fossil Fuels
Within the lifetime of an 18-year-old, petroleum
and natural gas will be consumed to the point
that they may no longer be used as fuel.
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Coal: The Carbon Rock of Ages
Coal is a complex mixture of organic material. It
is mostly carbon. Carbon combusts as follows:
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Coal: The Carbon Rock of Ages
Coal is ranked from low-grade peat and lignite to
high-grade anthracite.
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Coal: The Carbon Rock of Ages
Coal is abundant, and is by far the most plentiful
fossil fuel.
It is, however, hazardous to obtain and
inconvenient to use due to its solid nature.
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Coal: The Carbon Rock of Ages
Much coal contains sulfur, which when
combusted, produces sulfur dioxide (SO2), which
contributes to acid rain.
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Coal: The Carbon Rock of Ages
Coal is also a source of other chemical
substances.
When coal is heated in the absence of air, the
volatile compounds are driven off leaving coke,
which is used to produce iron and steel.
The volatile materials can be condensed into
coal tar, which can be used as a source of
organic compounds for medical and industrial
purposes.
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Coal: The Carbon Rock of Ages
The Carbon Cycle
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Natural Gas: Mostly Methane
Natural gas is one of
the cleanest burning
fossil fuels.
It can also be used as
a raw material for the
production of many
industrial chemicals.
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Petroleum: Liquid Hydrocarbons
By 1950, petroleum had displaced coal as a
principle fuel.
Petroleum is a complex mixture of
hydrocarbons.
Its combustion with oxygen can be represented
as follows:
2 C8H18 + 25 O2 → 16 CO2 + 18 H20
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Petroleum: Liquid Hydrocarbons
Petroleum comes from crude oil, which is
separated into fractions for use.
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Petroleum: Liquid Hydrocarbons
A fractional
distillation column
is used to refine
petroleum.
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Petroleum: Liquid Hydrocarbons
Larger fractions can be further refined by
cracking into smaller fractions.
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Petroleum: Liquid Hydrocarbons
Gasoline is a lighter fraction from crude oil. It is
actually a mixture of more than 150 different
compounds.
The gasoline fraction that comes from a
distillation column is called straight-run
gasoline and does not perform well in a
modern, high-compression automobile engine.
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Petroleum: Liquid Hydrocarbons
Octane Ratings of Gasoline
The octane rating of gasoline is a measure of
the fuel’s ability to resist knocking. Knocking
occurs when the fuel combusts before the spark
plug fires.
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Petroleum: Liquid Hydrocarbons
Octane Ratings of Gasoline
Isooctane is very resistant to knocking and is
assigned an octane rating of 100. Heptane is
given an octane rating of zero. Gasoline with an
octane rating of 90 performs the same as a
mixture of 90% isooctane and 10% heptane.
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Petroleum: Liquid Hydrocarbons
Octane Ratings of Gasoline
The octane ratings of gasoline can be improved
in a number of ways, including the catalytic
reformation of the low octane alkanes into cyclic
alkanes with higher octane ratings.
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Petroleum: Liquid Hydrocarbons
Alternative Fuels
Automobile engines can be made to run on
nearly any liquid or gaseous fuel.
Diesel fuels are mainly C9-C12 hydrocarbons.
Biodiesel is made from animal or vegetable fats
and oils.
Ethanol can be used. E-85 is a mixture of 85%
ethanol and 15% gasoline.
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Convenient Energy: Electricity
Convenience of fuels depends on the state of
matter.
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Convenient Energy: Electricity
Coal Gasification and Liquification
Solid coal can be made more convenient by
gasification and liquification.
Electricity is perhaps the most convenient fuel
of all.
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Convenient Energy: Electricity
Coal-Burning Power
Plant for the Generation
of Electricity
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Convenient Energy: Electricity
Percentages of
electric power
generation in the
U.S. in 2003 from
various sources.
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Nuclear Energy
Nuclear Fission
Nuclear power plants use fission reactions to
produce heat to generate steam to ultimately
turn a turbine to generate electricity.
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Nuclear Energy
The U.S. uses much less nuclear energy than
many developed nations do.
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Nuclear Energy
Nuclear power plants produce minimal air
pollution.
However, many elaborate and expensive safety
precautions must be employed.
Also, fission products (nuclear waste) must be
dealt with.
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Nuclear Fusion: The Sun in a
Magnetic Bottle
Controlled fusion presents many advantages
over fission reactors. Radioactive wastes would
be minimized. However, technical difficulties
must be overcome for fusion reactors to be a
reality.
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Nuclear Fusion: The Sun in a
Magnetic Bottle
The
electromagnet
called tokamak
is designed to
contain the high
temperature
and pressure
plasma of a
nuclear fusion
process.
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Renewable Energy Sources
Solar Energy
It has been noted that nearly all of the energy
available on Earth comes from the sun.
Energy from the sun is diffuse and must be
concentrated to make it useful.
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Solar Heating
Solar
collectors
absorb solar
energy and
use it to heat
water.
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Solar Cells
Photovoltaic cells
can be used to
convert solar energy
into electricity.
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Biomass: Photosynthesis for
Fuel
Burning plant material
by-products is one
means of harvesting
energy from the sun.
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Biomass: Photosynthesis for
Fuel
Combustion of
agricultural waste,
fermentation to ethanol
or methane, and the
fermentation of human
and animal wastes to
methane have all been
and are being used as
sources of energy.
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Hydrogen: Light and Powerful
Hydrogen can be burned cleanly as fuel or used
in fuel cells.
When hydrogen burns, it produces water and
energy.
2 H2(g) + O2(g) → 2 H2O(g) + 572 kJ
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Hydrogen: Light and Powerful
Fuel cells
oxidize fuel in an
electrical
chemical cell to
produce
electricity.
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Other Renewable Energy
Sources
Wind and Water
Both wind (windmills)
and water (dams and
hydroelectric plants)
have been used to
turn turbines and
produce electricity.
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Other Renewable Energy
Sources
Geothermal Energy
In a geothermal plant, water is pumped to the
interior of Earth, where it is heated and converted
to steam.
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Other Renewable Energy
Sources
Oceans of Energy
Ocean thermal energy has been shown to be
workable since 1932.
Also, tides and wave action can be converted to
useful energy with appropriate technology.
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Energy: How Much Is Too
Much?
The demand for energy is ever-increasing and
our useful sources are dwindling. These
competing demands will cause many changes in
our future.
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