# Slide 1 - GS105COCC

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```					Energy, Chemistry, and
Society-Part II
Experiment #8
Moles NaHCO3 to NaCl

Source: Michele Young
Experiment #10
Comparison of the Energy Content of
Fuels

August 10, 12 – Experiment #10
August 17, 19 – Experiment #11 (Biodiesel)
August 17 – Term paper due
August 24, 26 – Energy content Biodiesel
Experiment #10
Comparison of the Energy Content of
Fuels

1. Burn a fuel to heat water
2. Monitor temperature rise of known volume of water
3. 1 ml H2O = 1 g
4. Energy Content = fuel type + how much is burned

Example: CH4 + 2O2  CO2 + 2H2O + ∆ (heat)
CH3OH, C2H5OH, C3H7OH, C4H9OH,
C12H26 (lamp oil), C40H82 (candle wax)
Overview
heat absorbed (calories) = m x ∆T x 1.00 cal/gC

1. Assemble the apparatus and obtain a burner containing a known fuel.
2. Add a measured volume of water to the soda can and then determine the mass of
the water.
3. Weigh the burner.
4. Record the initial temperature of the water
5. Light the burner and heat the water until the temperature increases about 20C
6. Record the highest temperture of the water
7. Wight the burner again, in order to find the mass of fuel used.
8. Repeat with two or more additional fuel trials.
9. For each trial, calculate the amount of heat released per gram of fuel burned.
10. Calculate the calories of heat per 1 gram of fuel burned.
Kilimanjaro Summit
Ice Depletion
Melting Ice
 Where does the water go?
– Oceans
– By 2100 sea levels predicted to rise by 9-
88 cm (3.5 – 34.6 in)
– This endangers all costal cities – Seattle,
San Francisco, Boston, Miami
– Countries at sea level will be impacted:
the Netherlands
Impact of Rising
Temperatures on
Northern
Hemisphere
Snow Packs
Gases Regulated by Kyoto Protocol
Carbon Sequestration-
Capture/Storage
In the U.S., fossil fuel combustion provides
• 70% of electricity
• 85% of total energy

Fossil fuels produce large amounts of CO2

The supply of fossil fuels is finite, and may
be running out (estimates vary)
• 150 years left for coal
• 50 years left for oil
Energy Transformations

First Law of Thermodynamics:
Energy is neither created nor destroyed

Second Law of Thermodynamics
The entropy of the universe always
increases during a spontaneous process
Energy Transformations

First Law of Thermodynamics:
Energy is neither created nor destroyed
– Conservation of Energy
– Conservation of Mass
Energy can be converted from one form into
another
Energy Transformation
Second Law of Thermodynamics
The entropy of the universe always increases
during a spontaneous process
It is impossible to completely convert heat into work
without making some other changes in the universe
Organized energy is always being transformed into
chaotic motion or heat energy
Randomness is decreased only through a non-
spontaneous process (work must be performed)
Energy, work, and heat –
some definitions

 Energy – the capacity to do work
 Work is done when movement occurs
against a restraining force.
– The force multiplied by the distance
 Heat is energy that flows from a hotter to a
colder object.
– Temperature is a measure of the heat content
of an object.
Energy, work, and heat

 Both work and heat are forms of molecular
motion
– Work is organized motion (all the
molecules moving in the same direction)
– Heat is random motion (all the molecules
moving in different directions)
 Energy is the sum of all these molecular
motions
Entropy
 The more disordered a sample, the higher
the entropy
– Boiled egg vs. scrambled egg
– People sitting in a classroom vs. people
walking in the halls
– Gas vs. liquid vs. solid
– Photosynthesis vs. combustion
– Your desks vs. my desk
Entropy
 Another way of thinking about it… what is
the probability of a particular state?
 Your text uses the example of a drawer full
of socks
– A drawer full of socks is more likely to be
disordered than ordered
– It is not impossible for a drawer full of socks
to become organized…
– … but it does require work for that to happen
if you aren‟t willing to wait
Energy, work, and heat
Units of Energy
Joule
 The amount of energy required to raise a 1-
kg book 10 cm against the force of gravity
 The amount of energy required for each
beat of the human heart
Calorie
 Defined as the amount of heat necessary to
raise the temperature of exactly one gram
of water by one degree Celsius
 1 cal = 4.184 J
 1 “food calorie” = 1 kcal = 1000 cal
Energy Transformations

   Energy from fossil fuels
   Combustion
   Transform chemical energy to heat energy
   Engines transform heat energy into work
energy
Energy Transformation
Can we get complete energy conversion?
Does all the potential energy get
transformed into electricity (or even heat
energy)

Efficiency measures the ability of an engine to
transform chemical energy to mechanical
energy
Energy Transformation
Efficiencies are multiplicative
Overall efficiency = efficiency of (power
plant) x (boiler) x (turbine) x (electrical
generator) x (power transmission) x (home
electric heater)
How much energy does it take to heat
your house for a month – say, January?
How much methane does the power plant
need to burn in order to give your house
that much electrical power?
Overall efficiency = efficiency of (power plant) x
(boiler) x (turbine) x (electrical generator) x
(power transmission) x (home electric heater)
Overall efficiency = .60 x .90 x .75 x .95 x .98
Overall efficiency = 0.34
34 % energy generated is used
The rest is wasted
Energy Transformation

It takes about 3.5 x 107 kJ of energy to heat
a house in January
Methane releases 50.1 kJ energy per gram
Efficiency of electric heat using natural gas: 34%
Heat needed = heat used x efficiency
Heat used = (heat needed) / efficiency
= 3.5 x 107 kJ / .34 = 1.0 x 108 kJ
Methane used = 1.0 x 108 kJ / 50.1 kJ = 2.0 x 106 g
Energy Transformation
It takes about 3.5 x 107 kJ of energy to heat
a house in January
Methane releases 50.1 kJ energy per gram
What if you didn‟t use the power plant‟s electricity, but
just burned the methane yourself at home?
Efficiency of home heater using natural gas: 85%
Heat needed = heat used x efficiency
Heat used = (heat needed) / efficiency
= 3.5 x 107 kJ / .85 = 4.1 x 107 kJ
Methane used =4.1 x 107 kJ / 50.1 kJ = 8.2 x 105 g
Compared with 2.0 x 106 g methane to create
electricity at the power plant
Energy Transformation

 Potential Energy – energy stored in bonds,
or intrinsic to position
 Kinetic Energy – the energy of motion
 Thermal Energy – random motion of
molecules
 Entropy – randomness in position or energy
level
– Chaos
– Disorder
Formation of Water

 The overall energy change in breaking
bonds and forming new ones is – 498 kJ
 The release of heat corresponds to a
decrease in the energy of a chemical
system
 This explains why the energy change is
negative
Formation of Water
2 H2(g) + O2(g)  2 H2O(g) + energy
Reactants
Hydrogen (2 molecules, each with 1 H-H bond)
Oxygen (one O=O double bond)
Products
Water (2 molecules, each with 2 H-O bonds)

Energy is released because there is energy left over
872 kJ + 498 kJ – 1868 kJ = – 498 kJ (exothermic)
Energy as a Barrier to Reaction
 Activation energy – the energy necessary
to initiate a reaction
From Fuel Sources to Chemical Bonds

 Combustion of Propane, C3H8
-2024 kJ/mol
 Combustion of Ethanol, C2H5OH
-1281 kJ/mol
Energy as a Barrier to Reaction
 Low activation energies – fast reaction
rates
 High activation energies – slow reaction
rates
 Useful fuels react at rates that are neither
too fast nor too slow
 Smaller „bits‟ react faster than large „bits‟
 Increased temperatures help reactants to
get over activation energy barrier
Laboratory Teams

2 students
Per team
Lab 8 – Baking Soda to Table Salt

 NaHCO3 + HCl  NaCl + H2O + CO2

 Quantitative measurement: moles NaCl
from 1 mole NaHCO3
 Mole NaCl from Moles NaHCO3 is determined
gravimetrically
 Overview of the Experiment

– Label and weigh three test tubes
– Add a weighed quantity of sodium
bicarbonate to each test tube
– React the sodium bicarbonate with 10% HCl
– Evaporate the liquid remaining in the test
tube after the reaction takes place (NaCl,
must be DRY)
– Determine the weight of sodium chloride
produced
– Calculate the ratio of moles of NaCl formed to
moles of NaHCO3 used.
 Procedural Changes & Safety Notes

– Safety goggles for everyone
– 10% HCl – corrosive to skin/clothes
– Use Bunsen burner in the hood to evaporate
the water
– Point the open test tube away from your
partner and others
– Use boiling chips in the tubes to prevent the
solution from bumping during heating
– Too rapid heating will cause splashing
Combustion of Methane

 Total energy change in breaking bonds
1664 kJ + 996 kJ = + 2660 kJ
 Total energy change in forming bonds
- 1606 kJ + (-1868 kJ) = - 3474 kJ
 Net energy change
2660 kJ + (-3474 kJ) = - 814 kJ
From Fuel Sources to Chemical Bonds
This theoretical value (- 814 kJ) compares very
favorably with the experimental value (- 802.3
kJ). But it‟s not the same. Why not?
• In real chemical reactions, not all the bonds
are broken – just the pertinent ones
• In real molecules, not all bonds the same
type are energetically equal
 The O-H bond in water is not the same strength
as the O-H bonds in hydrogen peroxide, H2O2
• But we can calculate the energy of any
reaction as if these assumptions were true,
and get pretty close to the real answer
 The heat of combustion of methane is 802.3
kJ/mol. Methane is usually sold by the standard
cubic foot (SCF). One SCF contains 1.25 mol of
methane. What is the energy that is released by
burning one SCF of methane.

1.25 molCH 4    802.3 kJ
1 SCF CH 4                          1003 kJ
1 SCF CH 4    1 molCH 4
From Fuel Sources to Chemical Bonds
 Combustion – combination of the fuel with oxygen
to form products
CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g) + energy
 Exothermic reaction – any chemical or physical
change accompanied by the release of heat
 Heat of combustion – the quantity of heat energy
given off when a specified amount the a substance
burns in oxygen
– Typically reported in kilojoules per mole
(kJ/mol), but sometimes in kJ/g
– Most* combustion reactions are exothermic
From Fuel Sources to Chemical Bonds
 CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g) + energy
 Heat of combustion of methane is -50.1 kJ/g
– For every gram of methane burned we get 50.1 kJ
energy
16.0 g CH 4   50.1 kJ
1 mol CH 4                        802.3 kJ
1 mol CH 4 1 g CH 4
– For every mole of methane burned we get 802.3 kJ
energy
 The combustion of one mole of methane will always
produce one mole of carbon dioxide, two moles of
water, and 802.3 kilojoules of heat energy
From Fuel Sources to Chemical
Bonds

Energy change (DE) = Energyproducts – Energyreactants
The SIGN of the change is important!
Energy Changes at the Molecular Level

 Bond energy – the amount of energy that
must be absorbed to break a specific
chemical bond.
 Can be used to estimate heats of reactions
Bomb Calorimeter
Energy Consumption

 Pre-Historic man had only body and food for
fuel
– Used ~2000 kcal/day of energy
more technology
– Use 650,000 kcal/day of energy
– 65 barrels of oil or 16 tons of coal per person
per year
History of US energy
consumption by source, 1800 -
2000

History of US energy consumption by source, 1 EJ = 1018 J
Annual US energy consumption by source, 2002. „Other‟
includes wood, waste, alcohol, geothermal, wind and solar
Properties needed in a fuel

   Contain substantial energy content
   Plentiful
   Burn readily at just the right rate
   Others…
Energy Content
Fossil Fuels
 “You will die but the carbon will not; its career
and there a plant may take it up again in time,
sending it once more on a cycle of plant and
animal life”
– Jacob Bronowski in Biography of an Atom – And the
Universe.
Organic matter (plants, animals) decays upon
death, producing CO2 and H2O, just like in
combustion
But in some cases, decaying matter doesn‟t have
enough O2 around to complete the reaction
Other reactions take place deep in the earth at
high temperatures and pressures, producing
coal, petroleum and natural gas.
Fossil Fuels: Coal
 Was known in ancient times – used in
funeral pyres as early as 3000 B.C.
 Mining for coal was not common until
~1300 A.D., in Britain
 During the Industrial Revolution (beginning
in the 1700s), coal became the chief fuel
source in Britain, and later the rest of the
world
– Fuel was needed in vast quantities to
power the new Steam Engines
– Wood was already in short supply
Fossil Fuels: Coal
 Coal is a better energy source than wood
– Coal yields 30 kJ per gram
– Wood yields 12 kJ per gram

 Coal has higher ratio of carbon (85% by
mass)
– Fuels with a higher carbon ratio produce
more energy when they are burned
– An approximate molecular formula for
coal is C135H96O9NS
 As carbon content increases, so does the heat
content
 The less oxygen a compound contains, the more
energy per gram it will release on combustion
 “Better” coals have been exposed to higher
pressures for longer times, losing more oxygen
and becoming harder
Fossil Fuels: Coal
 Drawback #1: Difficult to obtain
– Underground mining dangerous and
expensive
– Since 1900 more than 100,000 workers killed
in American mine disasters – but how many
worldwide? And how many have been made
sick, or died from “black lung”?
 Drawback #2: Coal is a dirty fuel
– Soot
– Sulfur and nitrogen oxides
– Mercury
– Carbon dioxide
Fossil Fuels: Coal
 The benefit of coal: the global supply is
large
 20-40 times greater than petroleum

 Because of this, coal is expected to
become a much more important fuel in the
next 100-150 years

 It will become important to find ways to
better use coal – more cleanly, more
safely
Calculations Concerning Coal
1. Compute the amount of energy released by
burning 1.5 million tons of coal – the amount
consumed at an average coal-burning plant in
one year, assuming this coal produces 30 kJ per
gram

2. How much C is in 1.5 million tons of
C135H96O9NS?

3. How much CO2 would be produced from that
combustion?
C135H96O9NS
C + O2  CO2 + Energy
   135 mol C x 12.0 g/mol = 1620 g C
   96 mol H x 1 g/mol = 96 g H
   9 mol O x 16 g/mol = 144 g O
   1 mol N x 14 g/mol = 14 g N
   1 mol S x 32 g/mol = 32.1 g S
   1 mol C135H96O9NS = 1906 g/mol
   1620 g C per 1906 g Coal
C135H96O9NS
C + O2  CO2 + Energy
 1620 g C per 1906 g Coal
 [1 g = 1.1023 x 10-6 short tons (long, metric)]
 mass-to-mass relationship stays the same,
as long as same mass unit is used for both
 1620 tons C per 1906 tons Coal
 1.5 x 106 tons Coal (per year) x 1620 tons
C/1906 tons Coal = 1.3 x 106 tons C
 44 tons CO2/12 tons C x 1.3 x 106 tons C =
4.77 x 106 tons CO2
 (4.77 million tons per year-power plant)
Fossil Fuels: Petroleum
 Liquid - easy to pump to surface
 Transported via pipelines
 Higher energy content than coal
– 48 kJ/g for petroleum
– 30 kJ/g for coal
 Petroleum (crude oil) easily converted to
gasoline
 Around 1950, oil surpassed coal as the primary
fuel in the U.S.
 In 1998, the U.S. burned 125 billion gallons in
more than 203 million vehicles
 The U.S. consumes 25% world‟s oil … for 5% of
the population
U.S. petroleum product use, domestic production, and
imports. In 2002, more than 50% of total oil used in U.S.
is imported.
Sources of crude oil and petroleum products
imported by US (August 2003)
May 11, 2010
World Energy Consumption by Region
CO2 Emissions by Region 1990-2030
Mongabay.com
Rainforest News
Environmental News
http://www.mongabay.com

Summer from hell: seventeen nations hit all-time heat records
Jeremy Hance
mongabay.com
August 09, 2010

1. Belarus               2. Ukraine               3. Cyprus
4. Russia                5. Finland               6. Qatar
7. The Sudan             8. Saudi Arabia          9. Niger
10. Chad                 11. Kuwait               12. Iraq
13. Pakistan             14. Columbia             15. Myanmar
16. Ascension Island     17. Solomon Islands
Mongabay.com
Rainforest News
Environmental News
http://www.mongabay.com

Hottest Temperature ever recorded in Asia:

Pakistan-Summer 2010

128F
Mongabay.com
Rainforest News
Environmental News
http://www.mongabay.com

Officials point to Russian drought and Asian
deluge as consistent with climate change

2010 the second hottest year on record through May

Freak floods in US predicted by 2009 climate change
report

NASA satellite image reveals record low snow for
the United States
Mongabay.com
Rainforest News
Environmental News
http://www.mongabay.com

Monthly average
carbon dioixde
concentration
measured at the
Mauna Loa
Observatory in
Hawaii 1958-2005
Rising Sea Levels
& Rising Global
Temperatures
Fossil Fuels: Petroleum

 Crude oil must be refined
 Mostly hydrocarbons – molecules consisting
of hydrogen and carbon atoms
– Range from 1 to 60 carbon atoms per
molecule
 Mostly alkanes – hydrocarbons with only
single bonds between carbons
Oil Refinery
 Distillation –
purification, or
separation, process in
which a solution is
heated to its boiling
point and the vapors
are condensed and
collected
The higher the number of
carbons contained in the
molecule, the higher the
boiling point.

The most volatile
components of the
fractionating tower boil far
below room temperature
and are called refinery
gases.
Petroleum
 The gasoline fraction contains hydrocarbons with
5 to 12 carbon atoms per molecule
 One barrel of crude oil contains 42 gallons
 35 gallons of this is used for heating and
transportation
Manipulating Molecules
 Gasoline that comes directly from the
fractionating tower represents less than 50%
of the original crude
 Heavier and lighter fractions can undergo
chemical reactions to form more gasoline
Manipulating Molecules
 Cracking - a chemical process by which
large molecules are broken into smaller
ones suitable to be used in gasoline
– C16H34  C8H18 + C8H16
– C16H34  C5H12 + C11H22
 Thermal cracking – heat crude oil to high
temperature so it decomposes
 Catalytic cracking – lower temperature
process using a catalyst
Manipulating Molecules
 Catalytic combination – use a catalyst to join
smaller molecules together to form
intermediate sized ones
4 C2H4  C8H16
Manipulating Molecules
 Isomers –compounds
with the same chemical
formula but different
chemical structures.
– C8H18
– Octane – boiling point
125oC
– Isooctane – boiling point
99oC – ignites more
Internal Combustion Engine
http://auto.howstuffworks.com/engine1.htm
http://auto.howstuffworks.com/engine4.htm
Knocking
 Premature ignition during the compression
stroke
 Noisy and can damage the engine
 Octane rating of gasoline
The higher the number, the less likely the
gas will cause knocking
 Octane can be reformed to isooctane
 Oxygenated fuels are octane boosters
 Oxygenated gasolines –
blends of petroleum-
derived hydrocarbons with
oxygen-containing
compounds such as MTBE
(methyl tertiary butyl ether)
and ethanol.
 They reduce the carbon
monoxide emissions, since
fuel contains oxygen
(ethanol)
 Winter Oxyfuel Program (1992)
– Part of the Clean Air Act
– Reduce CO emissions
– During winter months, gasoline must contain
2.7% oxygen by weight
– Typically ethanol
 Year-round Reformulated Gasoline Program
(1995)
– Part of clean air act
– Reformulated gasolines (RFGs) are oxygenated
gasolines that also contain a lower percentage
of certain more volatile hydrocarbons, such as
benzene found in non-oxygenated conventional
gasoline
Reformulated gasolines
 <1% benzene
– Benzene is a carcinogenic compound
 >2% oxygenates
– Burn cleanly
 Evaporate less easily than conventional
gasoline
– Fewer smog-forming pollutants
 30% US gasolines are RFGs – with 90%
containing MTBE
MTBE
 In January 2004, the National Institute of Environmental
Health Sciences reported the human health effects of
short-term exposure to large or small amounts of MTBE
are not known.
 MTBE is very soluble in water and is finding its way to
drinking water
 Little likelihood that MTBE will cause adverse health
effects at concentrations of 40 ppb or below – above this
concentration one can taste it in the water
 California has phased out the use of MTBE in gasoline,
and many local governments in the Northeast have started
the same process
 Because this represents a huge market, most gasoline
providers have stopped using MTBE and have replaced it
with other additives – particularly ethanol
 Coal supply bigger than petroleum supply
 Convert coal into gaseous and liquid fuels

C  s   H 2O  g   CO  g   H 2  g 
coke                        water gas

CO  g   H 2  g   hydrocarbons
catalyst

water gas
 Biomass
– Materials produced by biological processes
– Wood
– Ethanol, CH3CH2OH
 Produced by fermentation of starch and
sugars in grains such as corn
 Can also be prepared commercially by the
reaction of water with ethylene (C2H4)
– Biodiesel
 Gasohol
– Mix 10% ethanol
with 90% gasoline
– Can be burned in a
standard car engine
 Ethanol produces
29.7 kJ/g of energy
 Octane produces
47.8 kJ/g of energy
Other Sources
 Flexible Fuel Vehicles
– Detect what the fuel
engine performance to
match
– Can use E85 – 85%
ethanol and 15% gasoline
– It is believed that most
FFV owners (4 million as
of 2006) are not aware
that their vehicles can run
on E85: fewer than 1% of
the consumed fuel is E85
Drawbacks of Ethanol as Fuel
 Not as much energy (gram per gram) as gasoline
 How much farmland would need to be diverted
from food production to get ample fuel
production?
 How much is needed? Estimates are that
California alone will consume 20% of the ethanol
produced in the U.S.
 Expense (\$\$ and Energy)
–   Energy required to plant, cultivate and harvest corn
–   Production and application of fertilizers
–   Distillation of alcohol
–   Tractors used in farming
–   More energy to produce a gallon of ethanol than
obtained from burning?
Biodiesel
 Can be used in any
standard diesel engine
 Natural and renewable
resources
– New and used
vegetable oils and
animal fats
 Burn more cleanly and
more efficiently than
Garbage Power
 140 U.S. power plants use garbage as fuel source
– Hennepin Energy Resource Company in Minneapolis
converts 365,000 tons of garbage per year into enough
energy to provide power to 25,000 homes
– One truckload of solid waste generates the same
amount of energy as 21 barrels of oil
– They‟ve since built a second facility that processes
another 235,000 tons
 Simultaneously addresses two major problems:
Energy and Waste
 Downside? Incineration process is efficient but
produces CO2
Garbage Power
 Methane Generators
– Animal and vegetable wastes are fermented
to form “biogas”
 60% methane
 Can be used for cooking, heating, lighting,
refrigeration, electrical generation
 The manure from 2 cows provides enough
energy to support a farm family
– Prevalent in China and India. In China, 2/3 of
rural families use biogas as their primary fuel

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