energy sources and the environment
DESCRIPTION
Section 1 – Fossil Fuels Energy Resources Energy is used all the time in nature Thermal energy – furnaces, stoves Mechanical energy – cars, vehiclesTRANSCRIPT
Energy Sources and the Environment
Chapter 8 Energy Sources and the Environment Section 1 Fossil Fuels
Energy Resources
Energy is used all the time in nature Thermal energy furnaces,
stoves Mechanical energy cars, vehicles Energy Transformation
The Laws of Conservation of Energy State: Energy cannot be created
or destroyed To use energy, energy must be transformed intoanother
form to perform a function Energy can be transformed to forms that
are notuseful Example:Electricity flowing through power lines 10%
is lost to thermal energy Energy Use in the United States
The US uses more energy than any othercountry in the world. The US
is an industrialized country Example:graphs from 2008 show
energyuses in the United States Fossil Fuel Formation What are
fossil fuels?
Coal Natural gas Petroleum (Crude oil) How are fossil fuels formed?
Formed from the dead and buried remains of onceliving organisms
over the course of many years Combustion Reactions How do we use
fossil fuels?
Fossil fuels contain energy in the form ofchemical potential energy
that is stored in fossilfuels Fossil fuels stored energy is far
higher than otherorganic substances Example:burning 1kg of coal
releases two to threetimes as much energy as burning 1kg of wood
Combustion Reactions Formation and Obtaining Fossil Fuels
How do fossil fuels form and how do we get them? Because they are
formed from once livingorganisms, fossil fuels are stored
naturallyunderground Fossil fuels must be mined Petroleum
Petroleum: a highly flammable liquid formed from thedecay of
organisms, such as plankton and algae Humans pump millions of
liters of petroleum every day A mixture of many different unique
chemicalcompounds Most are hydrocarbons Contain hydrogen and carbon
High energy bonds Bonds are broken when burned Fractional
Distillation
Because petroleum contains many different typesof hydrocarbons,
they must be separated Uses the process of fractional distillation
Fractional Distillation
This separation occurs in distillation towers at oil- refineries.
First, petroleum is pumped into the bottom of the towerand heated.
The chemical compounds in the petroleum boil atdifferent
temperatures. Materials with the lowest boiling points rise to the
top ofthe tower as vapor are collected. Hydrocarbons with high
boiling points, such as asphalt andsome types of waxes, remain
liquid and are drained offthrough the bottom of the tower.
Petroleum Use About 15 percent of the petroleum-basedmaterials that
are used in the United States arenot used for fuel In addition to
fuels, plastics and synthetic fabrics aremade from the hydrocarbons
petroleum. Lubricants, such as grease and motor oil, as well as
theasphalt used in surfacing roads, are made frompetroleum. Natural
Gas Natural gas: a fossil fuel composed mostly ofmethan, CH4, but
it also contains other gaseshydrocarbon such as propane, C3H8, and
butane,C4H10. of energy consumed in the US comes from usingnatural
gas Contains more chemical potential energy per kg thanpetroleum or
coal The cleanest burning fossil fuel Coal Coal: a solid fossil
fuel that is found in mines
Forms from ancient swamps Forms as plant material is buried
beneathsediments, decays, and compacts Before the 1900s more than
90% of homes wereheated by burning coal Today, less than 25% Coal
is often burned in power plants to generateelectricity Origin of
Coal Coal is a mixture of hydrocarbons and otherchemical compounds.
Compared to petroleum and natural gas, coalcontains more
impurities, such as sulfur andnitrogen-based compounds. As a
result, more pollutants, including sulfurdioxide and nitrogen
oxides, are produced whencoal is burned. Electricity Graph shows
the percentages of energy thatcomes from different sources in the
US Electricity Electricity
https://www.youtube.com/watch?v=rEJKiUYjW1E Power Plant
Efficiency
Not all the chemical potential energy in the fuelis converted to
electrical energy. No stage is 100 percent efficient. Thermal
energyis released into the environment. The overall efficiency of a
fossil fuel-burningpower plant is about 35 percent. The Cost of
Fossil Fuels
Using fossil fuels has some negative side effects When petroleum
products and coal are burned, smokeis given off the pollutes the
atmosphere with smallparticles Releases carbon dioxide Global
warming can occur as a result The Cost of Fossil Fuels
Most abundant fossil fuel is coal Coal contains more impurities
than oil or naturalgas Burning coal can release these impurities
into airthat is then breathed by organisms Coal mining can also be
dangerous Inhalation Risk of death or injury while mining
Nonrenewable Resources
Fossil fuels are nonrenewable resources They are not regenerated in
the earth as quicklyas they are used As human population increases,
production offossil fuel based products will continue toincrease,
reserves of fossil fuels will decrease Fossil fuels will become
more difficult to obtain To meet demands, some are looking
foralternatives such as shale deposits Nonrenewable Resources
Section 2 Nuclear Energy
Nuclear Fusion Fusion: when atomic nuclei combine at very
hightemperatures The Sun is a giant nuclear reactor This process
takes a small amount of mass and convertsit into huge amounts of
thermal energy Fusion is the most concentrated energy source known
Fusion-based power plants are not practical becausethe reaction
occurs at millions of degrees Celsius Fission Fission: energy
released when the nucleus of anatom splits apart Extremely small
amounts of mass are converted tohuge amounts of energy 9% of US
electricity is made using fission Nuclear power plants use thermal
energy to generateelectricity Nuclear Reactors Nuclear reactor:
uses the energy fromcontrolled nuclear reaction to
generateelectricity All reactors share common parts They will
contain: Fuel for fission Control rods Cooling system Nuclear
Reactors The core of a reactor is the smallpart where fission
occurs The core contains fuel rods andcontrol rods Control rods
absorb neutrons fromradioactive decay Water acts as a coolant to
removeheat Nuclear Fuel Only certain elements have nuclei that
canundergo fission. Naturally occurring uranium contains an
isotope,U-235, whose nucleus can be split apart. As a result, the
fuel that is used in a nuclearreactor is usually uranium dioxide.
Fuel Rods The core of a reactor contains about 100,000 kgof uranium
in hundreds of fuel rods Cores contain pellets of uranium dioxide
Tubes of fuel rods are bundled and covered inalloys For every kg of
uranium that undergoes fission, 1gof matter is converted to energy
1g of matter converted to energy = energygenerated by burning 3
million kg of coal Fuel Rods The Nuclear Chain Reaction
Uranium atoms split to release neutrons whichcauses other atoms to
split apart.This causes achain reaction When an atom of Uranium-235
(U-235) is hit by aneutron it splits into two smaller nuclei This
causes two or three more neutrons to beemitted Causes a large chain
reaction The Nuclear Chain Reaction A Constant Rate As the nuclear
chain reaction occurs heat is produced
Sometimes this can occur too fast creating too muchheat In this
case, cooling rods are used to absorb some ofthe neutrons and
prevent them from striking other U- 235 atoms By raising or
lowering the cooling rods, the reactioncan be sped up or slowed
This can allow for a constant rate to be found Benefits and Risks
of Nuclear Power
Nuclear power is used to generate electricity in asimilar way to
burning fossil fuels Nuclear power plants to do not produce the
samepollutants as fossil fuels and are cleaner Benefits and Risks
of Nuclear Power
Mining uranium can cause environmental damage They do risk a
nuclear meltdown Coolant from the core must be cooled
beforereturned to streams or rivers The Release of
Radioactivity
One of the most serious risks of nuclear power isthe release of
harmful radiation from powerplants. The fuel rods contain
radioactive elements withvarious half-lives. Some of these elements
could harm livingorganisms if they were released from the
reactorcore of a nuclear power plant The Disposal of Nuclear
Waste
Nuclear waste: any radioactive material thatresults when
radioactive materials are used. After about three years, not enough
fissionable U- 235 is left in the fuel pellets in the reactor
coreto sustain the chain reaction. The spent fuel contains
radioactive fissionproducts in addition to the remaining uranium.
Low-Level Waste Contain small amounts of radioactive material
Have short half lives By product of electricity generation,
medicalresearch and treatments, pharmaceuticalindustry, and food
preparation Low-level wastes are usually buried in trenchesabout
30m deep in special locations If dilute, some waste is released
into air or waterwhere it will dissipate High-Level Waste Generated
by nuclear power plants and nuclearweapons programs After a fuel
rod is spent, it is stored in a deeppool of water Many high-level
wastes have long half-lives High-level wastes remain radioactive
for tens ofthousands of years Must be stored in extremely stable
containers High-Level Waste One method of long-term waste storage
incasesradioactive wastes in glass and ceramic thenplaced in
protective metal containers Containers are then buried hundreds of
metersbelow ground in stable rock formations or saltdeposits
Section 3 Renewable Energy Resources
Energy Options Renewable Resources: an energy source that
isreplaced by natural processes faster than humans canconsume the
resource Demand for energy increases as Earths populationincreases
Other sources must be used to meet the demand Some alternatives are
renewable Energy From the Sun Photovoltaic cells: convert radiant
energy fromthe sun directly into electrical energy About 1
billionth of the suns energy strikes earth The suns energy should
last for billions of years its inexhaustible Solar energy is a
renewable resource Many devices use photovoltaic cells Example:
cars How Solar Cells Work Two layers of semiconducting material
betweentwo layers of conducting metal One layer of semiconductor is
rich in electrons;one is poor in electrons How Solar Cells Work
When sunlight strikes a solar cell, electrons areejected from the
electron-rich semiconductor. These electrons can travel in a closed
circuit backto the electron-poor semiconductor Parabolic Troughs
Focuses sunlight on a tube containing heat- absorbing fluid such as
synthetic oil or liquid salt Used in remote areas where electricity
is hard toget Best forms focus solar power into a receiver Heated
fluid is circulated through a boiler tomake steam Used in turbines
Energy from Water Steam can move a turbine
Running water can be used the same way GPE of water is increased if
a dam is used GPE is released when water flows through tunnelsat
the base Energy from Water Rushing water spins a turbine, which
rotates theshaft of an electric generator to produceelectricity
Hydroelectricity Electricity produced from moving water
8% of electrical energy in the US made byhydroelectric power plants
Very efficient with little pollution Reservoirs created by dams for
hydroelectricpower can be used for drinking water and crops
Electricity is cheap after initial setup costs Energy from Oceans
Every day ocean levels rise and fall
These tides can be used for hydroelectric power Water is trapped
behind a dam At low tide, water flows back out to sea usingturbines
to generate electricity Tide differences are limiting, only a few
places onearth have large enough tidal differences Waves and ocean
currents can also be used Wind Energy Windmills convert wind energy
into electrical energy
Wind spins a propeller connected to a generator Disadvantages are
that few places on earth haveenough wind to meet needs Renewable
resource Energy from Inside Earth
The thermal energy that is contained in hotmagma is called
geothermal energy. Heat is generated within Earth by the decay
ofradioactive elements. This heat is called geothermal heat.
Geothermal heat causes the rock beneath Earthscrust to melt. This
hot molten rock beneath Earths surface iscalled magma Alternative
Fuels The use of fossil fuels would be greatly reduced ifcars could
run on other fuels or sources of energy. Cars have been developed
that use electricalenergy supplied by batteries as a power source.
Hydrogen gas is another possible alternative fuel.It produces only
water vapor when it burns andcreates no pollution Biomass Fuels
Biomass is renewable organic matter, such aswood, sugarcane fibers,
rice hulls, and animalmanure. Biomass can be burned in the presence
of oxygento convert the stored chemical energy to thermalenergy.
Converting biomass is probably the oldest use ofnatural resources
for meeting human energyneeds. Section 4 Population and Carrying
Capacity
Population: all the individuals of one speciesliving in a
particular area Carrying Capacity: the largest number ofindividuals
of a particular species that theenvironment can support Since the
mid-1800s human population hasincreased at a rapid rate
Causes:advances in medicine, better nutrition,and availability of
clean water Population and Carrying Capacity
If natural resources are used too quickly, theenvironment is
threatened and populations suffer Irresponsible usage of earths
resources couldresult in us reaching our carrying capacity People
and the Environment
Pollutants: any substance that contaminates theenvironment You have
an impact Electricity you use comes from fossil fuels.Thiscan
affect the air you breath Water you use must be treated Impact on
Land Land is affected when fossil fuels are extractedfrom earth
Land: used for agriculture, forests, urbandevelopment, and waste
management Deforestation: the clearing of forest land
foragriculture, urban development, or logging Increases the amount
of carbon dioxide in theatmosphere Can cause increases in
atmospheric temperatures Urban Development Over time as population
grows, urbandevelopment increases Highways, office buildings,
parking lots Some communities, states, countries, and
privatebusinesses try to preserve natural areas bydesignating them
as historic sites or nationalparks Waste Hazardous Wastes: wastes
that are poisonous,causes cancer, or can catch fire Garbage affects
the amount of hazardous waste About 55% of garbage is disposed of
in sanitarylandfills The rest is recycled or burned National and
State Parks
National and state parks are areas of landprotected and preserved
by the government. The forests, wetlands and grasslands, and parks
inthe United States are safe from urbandevelopment, waste disposal,
and extensivedeforestation Impact on Water Life on Earth would not
be possible without water.
Plants need water to convert radiant energy intofood energy. Some
animals make water their homes. Sixty percent of the human body is
composed ofwater Sources of Water Pollution
Polluted water contains chemicals and organismsthat cause disease
Sediments can be pollutants Mining can release metals into water
Examples: mercury, lead, nickel, and cadmium Oil and gas can run
off Wastewater (sewage) contains human waste,household detergents,
and soaps Impact on Air Harms humans, plants, and animals
Dust from construction contributes Volcanoes and forest fires are
natural sources ofair pollution Types of Air Pollution
Photochemical smog: the pollution that resultsfrom the reaction
between sunlight and vehicle orfactory exhaust Acid precipitation:
sulfur-, nitrogen-, and carbon- based compounds released with
moisture in theair Types of Air Pollution Reducing Pollution Ways
to conserve resources
Composting yard and kitchen waste Low-flush toilets and leak-free
faucets will helpreduce water impact Bicycling or using buses can
help reduce impacton the air