Energy, Chemistry, and Society

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Chapter 4 Energy, Chemistry, and Society
In order to have a better understanding of the
topics discussed in these notes, you may want to
read the related chapters from the book. In the
exams you are responsible only sections of the
book which are discussed in the lecture notes.
This information and advice is valid for all
chapters.
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Total energy consumption
World Marketed Energy Consumption
2000 years ago 12,000 kcal energy spending per
person per day Today 650,000 kcal energy
spending per person per day translates into 130
workers of 2000 years per person today.
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US energy consumption by source over 200 years
World Energy-Related CO2 Emissions by Fuel Type
Energy Use by Type
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Annual US energy consumption by source in 2002
Watch the video
It is all about energy
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Conversion of suns energy into energy for muscles
In plants 2800 kJ 6 CO2 6 H2O
C6H12O6 O2 In Humans C6H12O6 O2
2800 kJ 6 CO2 6 H2O
Suns energy
glucose
glucose
Energy for muscles
Endothermic reaction A reaction which requires
energy input as it happens. The first reaction
shown above is an endothermic reaction, since
energy is an input. Exothermic reaction A
reaction which gives out energy as it happens.
The second reaction shown above is an exothermic
reaction, since energy is an output.
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E
Energy given out
Time
Exothermic reaction diagram
Exothermic reaction negative overall energy
(given out) 2 H2 O2 ? 2 H2O 498
kJ Endothermic reaction positive overall energy
(taken in)
Why coal, oil, H2 produces energy when reacting
with O2? When this molecules reacts with O2,
which means burned, results in the breaking of
the bonds in the molecules, which is a process of
releasing energy. Bonds posses energy which can
be released when the bonds get broken. Every
bond have different energy capacity which shown
in the table. The more bonds two atoms have, more
energy the bonds have. As the kinds of atoms
change at the each side of the bond, bond energy
changes too.
E
Energy taken
Time
Endothermic reaction diagram
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Coal gives 30kj per gram, better than wood as
energy source. Every coal is not the same, there
are different qualities of coal, US has medium
quality coal sources. Global supply of coal is
20-30 times greater than global
petroleum. Dependence on coal will increase
eventually if we cannot find another way. US has
the largest coal reserves on world. Drawbacks
1) Mining a) expensive, b) dangerous for miner,
c) environmental effects 2) Coal burning a) CO2
production, b) dirt forming, c) NO2, SO2
production d) ash 3) Transportation Since it is
solid it has to be carried by trucks What can be
done? Turning coal into liquid or gas form easy
to transfer reduce dirt form and other pollutions.
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Fig.04.13
US dependency to other countries for oil
Sources of crude oil imported by US, 2003
US 5 population, consumes 25 of oil
produced. OIL yields 50 more energy than coal.
Easier to transfer, creates less pollution than
coal. But has limited source. Middle east region
has the largest oil reserves in the world. Crude
oil must be refined to be turned into useful
products, such as Gasoline, wax, lubricants,
diesel, heating oil, asphalt, solvents Hydrocarbo
ns molecules only consist of hydrogen and carbon
atoms Alkanes, hydrocarbons with only single bonds
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These are the names of the carbon-hydrogen
containing compounds (alkanes). Their name is
based on the number of the carbons in them. Every
carbon must have four bonds carbons connected to
each other and hydrogen placed on carbons to make
them four bonded You need to know names and
formulas upto fsiz carbons systems. General
formula CnH2n2
Crude oil refinery tower
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Diagram of fractioning tower in refinery
Distillation purification or separation process
in which a solution is heated to its boiling
point and vapors condensed and collected
(purification of mixtures based on boiling point
of the compounds in the mixture)
Higher the of Cs in a molecule, higher the
boiling point it has. Hexane (C6H14) boils at
higher degree than ethane (C2H6)
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Fig.04.16
Boiling point increases
Natural Gas is mostly just Methane gas (CH4). It
can be used to produce energy. It is much
cleaner source of energy than oil and coal.
Russia has the largest natural gas reserves in
the world. It produces minimal amount of CO and
SO2. Also 30 less CO2 than oil.
watch video at
http//youtube.com/watch?v3qIBFc53eIY
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Isomer Different compounds with same formula
with different structure Octane (C8H18) and
isooctane (C8H18) Ethanol(C2H6O) vs
Ether(C2H6O) Both compound have same heat
of combustion but later ignites much more
easily. Octane rating gasolines resistance to
knocking in engines. Isooctane given 100 as a
reference. Higher the octane rating better as
gasoline and better for your car, since it
produce less knocking and better fuel ignition.
87 octane gasoline means that mixture of
gasoline has same knocking characteristics as a
mixture of 87 isooctane. It is obtained by
adding various chemicals.
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Octane enhancer octane rating of gasoline can be
increased by addition of chemicals to get better
ignition with higher oxygen content. Tetraethyl
Lead (TEL) was one of them, but was banned b/c of
toxicity. MTBE (methyl tertiary butyl ether).
is the second generation octane enhancer. 30 of
gasoline sold in US has MTBE. Leaks in pipelines
of oil let MTBE gets into water sources. CA
decided to phase out the use of it. High doses of
MBTE have shown adverse effects on nervous system
of animals, but small doses health effects are
unknown. Ethanol (in 10 ratio) can be used as
additive for octane enhancer too. CA wants to
replace MTBE with ethanol. Most of gas sold
currently contains 10 ethanol.
MBTE warning on a gas pump.
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Alternative energy sources Ethanol 10
ethanol/gasoline mixture can be used without any
engine modifications. E85 means 85 ethanol 155
gasoline, which requires a special engine. FFV
(flexible fuel vehicles) can use E85 and normal
gasoline interchangeably. There are 3million FFV
out there by year 2005. In Brazil, 30 of the
vehicles are using pure ethanol as fuel. Ethanol
is cleaner than gasoline. Ethanol can be
obtained by the fermentation of the starch and
sugars. Today mostly corn is used as a source for
starch and sugars. Drawbacks a gram of ethanol
produces less energy than a gram of gasoline.
Using valuable farmland and feedstock for fuel
produce It is not ethical in large scale. If you
replace gasoline with ethanol, most of the
cropland has to be dedicated to produce corn in
order to meet the demand which will result in
lack of all the other stuff needed, which may
result in the increase of food prices. Ethanol
is a renewable energy source, but it requires to
plant, cultivate, harvest the corn, and to
produce and apply fertilizers, to distill the
alcohol, and manufacture of tractors, which all
requires enormous amount energy to accomplish.
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Alternative energy sources Biodiesel Renewable
energy source from used/or new vegetable oils and
animal fats. It can be used as a pure fuel or
blended with gasoline. It is cleaner than
gasoline. 8 of diesel consumption today is
biodiesel. Drawback more expensive than
gasoline. Garbage Garbage can be turned into
energy by burning. It will reduce 90 of the
environmental impact of the garbage by converting
garbage into CO2 and H2O. One truckload of
garbage gives energy equivalent to 21 barrels of
oil. Biogas Methane gas (CH4) can be generated
from garbage and farm animal waste (via
fermentation) which can be used as energy source.
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Chapter 8.4, 8.5, 8.6
Alternative energy sources
Hydrogen fuel cells developed using proton
exchange membrane (PEM). H2 O2 ? H2O is the
reaction taking place using platinum based
catalysts. Fuel cell is a galvanic cell that
produces electricity by converting chemical
energy of a fuel into electric without burning
the fuel. Advantages Not flame required (safe),
quit process (less vibration), less mechanical
engine problems, efficient for generating
electricity. Problems Hydrogen storage is a
big problem to use in cars. Alternative is
using Methanol (CH3OH) and reacting with H2O in
fuel cells by using different catalysts.
Methanol-PEM based buses are running today in
DC and Chicago. There are cars run on
electricity (EV-1) produced by different
manufacturers. They do not release any harmful
chemicals out.
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Why Hydrogen Hydrogen has the highest energy
content per unit weight, but not per unit volume,
of any fuel The Hydrogen initiative put forth
several specification targets over the course of
the plan. These goals include energy output,
costs, energy storage, and operating conditions
among a few. Currently Fuel cell systems in the
transportation sector would cost the consumer 3-5
times more than the typical internal combustion
engine. Materials and manufacturing costs are
currently too high for catalysts, bipolar plates,
membranes, and gas diffusion layers. The fuel
cell that is most promising for the
transportation industry is the Polymer
Electrolyte Membrane or Proton Exchange
Membrane. Advantages a) Solid electrolyte
reduces corrosion and electrolyte management
problems, b) Low operating temperature, c) Quick
start up Disadvantages a) Requires expensive
catalysts, b) High sensitivity to fuel
impurities c) Low temperature waste heat
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Chapter 8.7
Alternative energy sources
Hybrid vehicles combines conventional engines
with battery technology. Toyota Prius is an
example It runs on 50 less Gasoline. The other
50 is from the electricity generated by the
battery. They use regenerative braking process
as you decelerating or braking, the energy is
used by the generator to recharge the batteries.
They give 60 mpg in city, which 2 times of a
normal car. 50 less gasoline means 50 less
hazardous gases or materials. Solar Energy
(or photovoltaic cells) converts sun energy into
electrical energy without using any fuel. They
are only 15 efficient in converting suns energy
to electrical energy, which requires big panels
of solar cells to generate enough for good use.
But panels on a roof of house will generate
enough energy for hot water usage of the house.
Having roofs only from solar cell panels will
generate enough for the heating of the house as
well. It is expensive for set-up but it is only a
one time cost, which does not needs any input
afterwards.
Watch the video
http//youtube.com/watch?vwSI7YHwBFEE
http//youtube.com/watch?vUwVmPJJZXjg
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Alternative energy sources
Wind power is the conversion of wind energy into
more useful forms, such as electricity, using
wind turbines. At the end of 2006, it produces
just over 1 of world-wide electricity use, it
accounts for approximately 20 of electricity use
in Denmark, 9 in Spain, and 7 in Germany.
Globally, wind power generation more than
quadrupled between 2000 and 2006. Most modern
wind power is generated in the form of
electricity by converting the rotation of turbine
blades into electrical current by means of an
electrical generator.
Wind Energy
Watch the video
As a general rule, wind generators are practical
where the average wind speed is 10 mph or
greater. Usually sites are pre-selected on basis
of a wind atlas, and validated with wind
measurements
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Nuclear energy Nuclear energy is produced by a
controlled nuclear chain reaction and creates
heatwhich is used to boil water, produce steam,
and drive a steam turbine. The turbine can be
used for mechanical work and also to generate
electricity. As of 2004, nuclear power provided
6.5 of the world's energy and 15.7 of the
world's electricity, with the U.S., France, and
Japan together accounting for 57 of nuclear
generated electricity. As of 2007, there are
439 nuclear power reactors in operation in the
world, operating in 31 countries France produces
the highest percentage of its electrical energy
from nuclear reactors80 as of 2006. Nuclear
power gives France the cleanest air of any
industrialized country, and the cheapest
electricity in all of Europe The role of nuclear
power in meeting future electricity demand will
increase, given concerns about rising fossil fuel
prices, energy security, and greenhouse gas
emissions. On the other hand, issues related to
plant safety, radioactive waste disposal, and the
proliferation of nuclear weapons, which continue
to raise public concerns in many countries, may
hinder the development of new nuclear power
reactors.
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Nuclear energy The safe storage and disposal of
nuclear waste is a significant challenge. The
most important waste stream from nuclear power
plants is spent fuel. A large nuclear reactor
produces 3m3 of spent fuel each year. Two
Solutions currently a) storage indefinitely, or
b) reprocessing it for reuse and decrease the
mount of waste. Nobody wants storage facility in
their backyard! US stores its nuclear waste.
Underground storage at Yucca Mountain in U.S. has
been proposed as permanent storage. After 10.000
years later, stored waste should not pose any
public risk. France reprocesses its nuclear
waste to reduce its mass and make more energy.
Reprocessing can potentially recover up to 95 of
the remaining uranium and plutonium in spent
nuclear fuel Reprocessed material such as
plutonium can be used in nuclear
weapons. Several large studies in the US,
Canada, and Europe have found no evidence of any
increase in cancer mortality among people living
near nuclear facilities.
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Oil, coal, and natural gas consumption is
expected to increase 50 in next 10 years which
will result in 50 increase in CO2 emissions.
SUV produces 80, pick-up truck 67 more CO2 than
a large full-size car.
Solution to Energy Crisis conservation of
energy changing bulbs with energy efficient bulb
or with fluorescent bulb (white). Turn off TV
completely before going bed. Do not leave
cell-phone charger plugged in. Buy smaller cars.
Buy hybrid cars which uses 50 less gasoline.
Increasing the use of solar and wind energy
sources.
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Fig.04.02
Production and transfer of energy from facility
to your home
Heat energy that flows from hotter to colder
object. Heat is consequence of the motions of
the molecules. As the water absorbs heat, they
move faster. Temperature and the heat are not
the same. Temperature is the property of that
determines the direction of heat flow. A bottle
of water and the sea might be at the same
temperature, but sea will have more heat Since it
has more molecules at the same temperature.
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First law of thermodynamics energy neither
created nor destroyed. Energy often changes
forms, but the energy of the universe stays
constant. Second law of thermodynamics it is
impossible to convert heat to work
completely, What ever you are using will become
entropy. Entropy is the randomness of the energy
or the motion of the molecules. Entropy of
universe is increasing, which means useful
energy is being converted into chaotic motion or
heat. The reason is universe flows from less
probable to more probable. That is why
non-spontaneous orderly events will not occur
with work (energy) done by someone. Eg. Entropy
increase as Ice water vapor because motion
increases so the entropy. As things get less
ordered, more chaotic, entropy increases.
Examples When you make cake, entropy decreases,
since you bring things together. As you get
dressed entropy decreases. As you get untidy,
entropy increases.
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Problems
Fill in the structure with hydrogens Which of
them are the same Which of them are the isomer
These two containers are at the same
temperature. Do they have same heat?
What are the names of the following
compounds? CH4, C3H8, C5H12 Which has highest
boiling point? Propane, methane, ethane, hexane
Is this diagram belongs to an endothermic
or exothermic reaction?
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ANSWERS
Fill in the structure with hydrogens Which of
them are the same Which of them are the isomer 2
and 3 are same 1 and 2/3 are isomers
These two containers are at the same
temperature. Do they have same heat? they have
different heat content
What are the names of the following
compounds? CH4 Methane, C3H8 Propane, C5H12
Pentane Which has highest boiling point? Propane
(carbon C3), methane(C1), ethane(C2), hexane
(C6)
Is this diagram belongs to an endothermic
or exothermic reaction? Exothermic