NCEA L1 Science 2013 Chem 13 Understand that matter including carbon is made up of particles atoms An atom is the smallest neutral particle that makes up matter The type of atom and the way these atoms are arranged and connected to each other determines the type of matter ID: 794241
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Slide1
Chemistry
NCEA L11.3 Carbon Chemistry
NCEA L1 Science 2013
Chem
1.3
Slide2Understand that matter, including carbon, is made up of particles /atomsAn
atom is the smallest neutral particle that makes up matter. The type of atom and the way these atoms are arranged and connected to each other determines the type of matter – and therefore the physical
and
chemical
properties of the matter.
NCEA L1 Science 2013 Chem 1.3
Slide3Atoms have a particular structure – protons, electrons and neutrons
This is known as the Bohr model. Atoms have a central nucleus. The nucleus
contains
protons
(p) and
neutrons (n). Electrons (e) orbit the nucleus, arranged in shells or energy levels.
P
P
N
N
N
P
N
P
P
N
N
P
Electron -ve
Nucleus
Neutron
Proton +ve
Shell 1
Shell 2
NCEA L1 Science 2013 Chem 1.3
Slide4NCEA L1 Science 2013 Chem 1.3
Carbon has four valence electrons. The electronegativity of carbon is too small for carbon to gain electrons from most elements to form C
4-
ions, and too large for carbon to lose electrons to form C
4+
ions. Carbon therefore forms covalent bonds with a large number of other elements, including the hydrogen, nitrogen, oxygen, phosphorus, and sulfur
.
Groups of compounds in which the main atom in the molecule is carbon belong to a category known as
organic compounds
.
Carbon chemistry
Slide5NCEA L1 Science 2013 Chem 1.3Covalent bonding between atoms
Covalent bonding
occurs where
valence electrons
around atoms are
shared between neighbouring atoms.
This type of bonding is found between the C and H atoms in hydrocarbons and the C, H and O atoms in alcohol and is called
intramolecular
bonding. This bonding is very strong. The bonding between molecules is called
intermolecular
bonding and this is much weaker. When hydrocarbons are heated and they change state into liquids and gases it is this bonding that is broken
not
the covalent bonding.
Note the distinction:
Intra-molecular Forces
: the strong bonding forces within a molecule. i.e. the covalent bonds holding the molecule together.
Inter-molecular Forces: the weak bonding forces between molecules due to the attractions between partial charges.
Slide6NCEA L1 Science 2013 Chem 1.3Covalent bonding between atoms
H
H
C
x
x
Lewis diagram of
CH
4
(methane)
Bonded pair
Hydrogen electron
Carbon
electron
H
H
x
x
Lewis diagrams can be used to show how atoms are arranged in a molecule and which valence electrons are used in bonding. A bonding pair of electrons can also be shown as a line:
H
H C H
H
Slide7Molecular Formula
– type and number of each atom.
i.e. Propane C
3
H
8
Structural Formula
– placement of each atom.
Condensed Structural Formula
CH
3
-CH
2
-CH3
Structural isomers are molecules with
the same molecular formula but different structural formula.
How many ways can you draw C6H14 ?
Organic chemistry formula
NCEA L1 Science 2013 Chem 1.3
Slide8NCEA L1 Science 2013 Chem 1.3Alkanes
Compounds that contain only carbon and hydrogen are known
as
hydrocarbons
. Those that contain as many hydrogen atoms as possible are said to be
saturated
. The saturated hydrocarbons are also known as
alkanes
.
Slide9Straight-chain hydrocarbons
, in which the carbon atoms form a chain that runs from one end of the molecule to the other .i.e. butane
Alkanes
also form
branched
structures. The smallest hydrocarbon in which a branch can occur has four carbon atoms. This compound has the same formula as butane (C
4
H
10
), but a different structure. Compounds with the same formula and different
structure are called
structural isomers.
Alkanes
generic formula C
n
H
2
n
+2
NCEA L1 Science 2013
Chem
1.3
Slide10Sources of Alkanes
NCEA L1 Science 2013 Chem 1.3Alkanes are found in petroleum (either crude oil or natural gas). They are formed by the
anaerobic
decomposition of marine plant and animal organisms. The main components in new Zealand natural gas are methane (one carbon alkanes) and carbon dioxide.
Crude oil is imported into New Zealand from other countries and contains a mixture of different hydrocarbons with different length carbon chains. The different chain length hydrocarbons are separated by a process called
fractional distillation as they have different boiling points.
Slide11Prefixes are used to name the longest carbon chain
NCEA L1 Science 2013 Chem 1.3
Slide12NCEA L1 Science 2013 Chem 1.3
Write
the name of the alkane as
–
Identify the longest C chain
Write
the name
Prefix
of long chain
-
ane
Naming straight chain alkanes
Slide13Slide14Non reactivity of alkanes
(in relation to acids, alkalis, metals, water, because they are non-polar molecules).
Low melting and boiling points
– intermolecular forces are weak van der Waal forces.
Odour
– hydrocarbons are volatile because they have weak intermolecular forces and they have characteristic smells.
Do not conduct heat or electricity.
As the C chain gets longer the hydrocarbons change from gas to liquid to solid.
Combustion of alkanes. Alkanes are very good fuels. You must know the equations for
complete and incomplete combustion.
You must know that the products of combustion for both complete and incomplete combustion
.
Alkanes are non-polar so they are
not soluble in water
Chemical properties of alkanes
NCEA L1 Science 2013 Chem 1.3
Slide15Alkane reactions -substitution
Alkanes are
saturated
molecules, that is that every carbon atom has the maximum amount of atoms bonded to it. If any other atoms are to be added to an alkane one atom must be removed first.
This reaction is known as a
substitution
reaction. For this reaction to proceed enough energy must be available to overcome the activation energy required to break the strong C-H bond. The available site can then be occupied by the provided atom. This energy may be provided by heat or UV light
NCEA L1 Science 2013 Chem 1.3
Slide16NCEA L1 Science 2013 Chem 1.3Alkenes
Alkenes are known as
unsaturated
hydrocarbons. The carbons do not contain
as many hydrogen atoms as possible
because two or more carbons are joined by a double bond. Each carbon atom involved in the bond shares two of its valance electrons therefore four electrons (in two pairs) are involved in the covalent bond.
Slide17Functional Group
– One double carbon-carbon bond C=C
A
functional
group is the part of the molecule responsible for
reactions typical of the homologous series.
Alkene Nomenclature
Alkenes are named in a similar way to alkanes,
but the longest continuous carbon chain is numbered to give the carbon atoms in the double bond the lowest possible numbers
.
The position of the double bond is given by the smaller number of the two carbon atoms involved.
After
numbering the longest chain C1-C2=C3-C4,
the
compound is named 2-butene or but-2-ene,
but not 3-butene nor but-3-ene.
generic formula C
n
H
2
n
Alkenes
NCEA L1 Science 2013
Chem 1.3
Slide18NCEA L1 Science 2013 Chem 1.3
Number carbons so double bond has the lowest number.
Write
name as
1. Prefix
of long chain
2.
Location of C=C
3. –
ene
Naming
alkenes
Slide19Alkenes are
unsaturated
molecules, that is that not every carbon atom has the maximum amount of atoms bonded to it because it has one or more double bonds. If another atom is added to an alkene the double bond can be broken down to a single bond and the available site can be occupied by another atom.
This reaction is known as an
addition
reaction. This reaction has a lower activation energy requirement than substitution, that is it requires less energy to break a double bond than break a C-H bond, therefore it can proceed easier than a substitution reaction.
Break this bond
Two places to bond atoms to
Addition reactions
NCEA L1 Science 2013
Chem
1.3
Slide20NCEA L1 Science 2013 Chem 1.3
Alkenes undergo addition reactions - this means they can undergo addition of a halogen atom (chlorine, bromine, iodine) across the double
bond
to form a
haloalkane
.The common test for an unsaturated hydrocarbon (alkene) to distinghuish
it from a saturated hydrocarbon (alkane)
is therefore the
rapid
decolourisation of an orange solution of bromine. This occurs both in the presence or absence of sunlight
compared with the slower decolourisation (only with
uv
light) of the alkanes.CH3
CH=CH2 + Br2
1,2-dibromopropane
Addition reactions
Slide21Alkane – single bonds, saturated hydrocarbon
Alkenes – at least one double bond, unsaturated hydrocarbon
Subsitution – one (or more) hydrogen replaced by another atom
Addition reaction – double bond breaks and atoms added
Halogenation (Bromine)
Orange colour fades slowly in UV light
Halogenation (Bromine)
Orange colour disappears immediately changes to
haloalkane
Acidified Potassium Permanganate
Doesn’t react – solution remains purple
Acidified Potassium Permanganate
Purple to colourless – oxidation changes to alcohol
We can use these to identify whether the molecule is an alkene or alkane
Tests to distinguish between Alkanes and Alkenes
NCEA L1 Science 2013 Chem 1.3
Slide22NCEA L1 Science 2013 Chem 1.3
AlcoholAlcohols are not considered hydrocarbons as they have one or more oxygen atoms attached in addition to the hydrogen and carbon atoms. Alcohols are organic substances however and share many of the same chemical and physical properties of the alkanes and alkenes. Alcohols are used
as
solvents and
fuels and ethanol
(a two carbon alcohol) is used as a drink.
Slide23Functional group is the hydroxyl group –OH (not a hydroxide
)
Naming alcohols
Prefix
of long chain
an-
Location of
OH
-
ol
Alcohol
NCEA L1 Science 2013
Chem
1.3
Slide24NCEA L1 Science 2013 Chem 1.3
Small alcohol molecules are polar and the presence of the OH group means they are able to undergo intermolecular
hydrogen bonding
. The large difference in electronegativity
(ability to “grab” electrons from another atom due to their pull from the
combined
positive protons in their nucleus) between
the O and H atoms means the O-H bond is very polar and the slightly positive charge on this H atom is attracted to the non-bonding electron pairs of the oxygen on another molecule.
Physical properties
: This
means small alcohol molecules are
highly soluble in water
. However as the length of the non-polar hydrocarbon chain increases this solubility in water decreases.Chemical properties
: Aqueous solutions are neutral. The presence of the OH group in this molecule is NOT the same as the OH- in sodium hydroxide, NaOH (an ionic compound). Alcohol properties
Slide25NCEA L1 Science 2013 Chem 1.3Summary of solubility in Water –Alkanes and Alkenes
NCEA L1 Science 2013 Chem 1.3
Alkanes and Alkenes:
Not soluble in water.
These molecules are non-polar (there is no negative or positive ends to the molecule) compared with water which is polar (having a negative area near the oxygen atom and positive area near the hydrogen atoms) so they are not attracted to each other. Alkanes and alkenes
are
immiscible
(
two
or more liquids that will not mix together to form a single homogeneous
substance) and form a distinct layer from the water. Smaller C chained alkanes and alkenes are less dense than water and float on top.
If either an Alkane or Alkene is mixed into water eventually the two liquids will
form
separate
immiscible layers
Slide26NCEA L1 Science 2013 Chem 1.3
Summary of solubility in Water –Alkanes and Alkenes
Alkanes and water do not mix.
Hydrogen bonds between water molecules
Weak intermolecular bonds between alkane molecules
Because attractions between water and alkane molecules are different from the water – water and alkane – alkane attractions the two types of molecules stay separate
The less dense alkane floats on top of the water
Slide27Summary of solubility in Water - Alcohol
NCEA L1 Science 2013
Chem
1.3
Alcohols:
Soluble in water.
These molecules are polar (due to the –OH end) and water, also being polar, will bond with the alcohol. The alcohol molecules will therefore disperse and mix within the water molecules.
At the instant ethanol and water are mixed the ethanol floats on top of the water
Because the attractions between their molecules are similar, the molecules mix freely, allowing each substance to disperse into the other
Hydrogen bonds between ethanol molecules.
Hydrogen bonds between water molecules.
Hydrogen bonds between ethanol and water molecules.
Ethanol and water mix.
Slide28NCEA L1 Science 2013 Chem 1.3Summary of Boiling points
Alkanes: The smaller the alkane molecule the lower the boiling point and the more volatile (easier to combust) the alkane. As the molar mass (Mass number of all the atoms combined) increases, the boiling points also increase as the strength of the intermolecular (between molecules) attractions increases. The alkanes methane to butane (C1 – C4) are all gases at room temperatureAlkanes with between 5C and 15C atoms are all liquidsAlkanes with over 15 C atoms are soft solids
Alkenes: The boiling point trend is similar to alkanes where the larger the number of C atoms in the chain the higher the boiling point. The equivalent length C chain alkene has a slightly higher point than that of the alkanes.
Alcohols:
The boiling point trend is similar to
both alkanes and alkenes where
the larger the number of C atoms in the chain the higher the boiling point
.
The boiling point is higher than both alkanes and alkenes as the intermolecular bonding is stronger due to being a polar molecule– which creates a positive and negative end and hold the individual alcohol molecules together stronger and thus needs more energy to break them (heat energy)
Even small chain alcohols are liquid at room temperature
Slide29NCEA L1 Science 2013 Chem 1.3
Summary of Boiling points
Slide30Addition polymers
are formed when alkene monomers undergo addition to form a polymer eg. polythene from ethene, P.V.C. from vinyl chloride (chloroethene), polypropene from propene.
n(CH
3
CH=CH
2)
Addition polymers
NCEA L1 Science 2013
Chem
1.3
Slide31Monomers - smallest repeating unit with a double bond
Polymers – long chains of monomers joined together
Polymerisation – breaking of the double bond of each monomer and joining together with single bonds
MONOMERS
POLYMER
polymerisation
Addition polymerisation
NCEA L1 Science 2013
Chem
1.3
Slide32NCEA L1 Science 2013 Chem 1.3
Uses and importance of polymers from ethene and propeneThe alkenes are used to make
polymers (which we also refer
to
generally as plastics).
The chemical properties of these polymers such as low
chemical
reactivity with air, water and many
chemicals
make
them ideal as containers for liquids and chemicals
as they will not corrode or
decompose. Polymers
are also ideal as
clothing that can
be washed repeatedly
.
Slide33NCEA L1 Science 2013 Chem 1.3The physical properties of polymers such as their density (low) and strength make them ideal for strong yet light containers and clothing. Their ability to be melted and shaped makes production of
moulded shapes efficient and cheap, as well as making polymers easy to recycle and reuse.
Uses and importance of Polymers from
ethene
and propene
As polymers are insoluble in water they will not dissolve when exposed to water.
Polymers
are thermal and electrical insulators they have many uses in electrical applications, appliances and insulating wires.
Slide34NCEA L1 Science 2013 Chem 1.3Uses and importance of Polymers from ethene and propene
Examples:Polythene, made from ethene, is very cheap and strong, and is easily molded
. It is used to make, for example, plastic bags, bottles, and buckets
.
Polypropene
, made from propene, has strong fibers and a high elasticity. It is used, for example, in the manufacture of crates, ropes, and carpets
Slide35Combustion of Alkanes
Combustion
of hydrocarbons involves the breaking of bonds
between the atoms
,
(as opposed to melting) either
with plentiful oxygen – complete combustion, or limited oxygen – incomplete combustion. The products formed are water plus CO
2
(or CO/C with limited oxygen).
NCEA L1 Science 2013 Chem 1.3
Slide36Combustion of AlkanesComplete combustion
Alkane + Oxygen → Carbon Dioxide + water Incomplete combustionAlkane + limited oxygen → Carbon Monoxide or Soot + Water
NCEA L1 Science 2013 Chem 1.3
Slide37NCEA L1 Science 2013 Chem 1.3Complete combustion: needs plentiful O2
/ good ventilation. Flame burns clear / blue. The products are CO2 and H
2
O
Energy efficient - maximum amount of energy in hydrocarbon released
Combustion
Incomplete combustion:
occurs in limited O
2
/ poor ventilation. Flame burns dirty yellow/orange. The products CO and C (soot) and H
2
O.
Reduced energy efficiency – less than the maximum amount of energy in hydrocarbon is releasedAs C chain length increases you get more incomplete combustion occurring as bigger molecules need more O
2 from complete combustioncomplete
incomplete
Slide3838
Combustion Equations
Step 1. Write down the molecular formula of the alkane plus O
2
on the left hand side
Step 2. Write down CO
2
plus H
2
O on the right hand side
Step 3. Add the number of carbon atoms in the Alkane and balance the number of CO
2
(same as number of Cs)
Step 4. Add number of Hydrogen atoms in the Alkane and balance the number of H
2O (will be half number of
Os)Step 5. add the total number of Os on the RHS and balance the LHS of O2 (if there is an uneven number then you can use ½
Os)
Incomplete combustion
For limited oxygen replace CO
2
with CO and use same steps
For very limited oxygen replace CO
2
with C and use same steps
Combustion equations
NCEA L1 Science 2013 Chem 1.3
Slide39Combustion
Complete Alcohol + 1
1/2
Oxygen CO
2 + 2H
2
O
Incomplete Alcohol + 1 Oxygen CO + 2H
2
O
The longer the chain of carbons in the alcohol the less vigorously the combustion reaction. Methanol and ethanol (drinking alcohol) combust more readily.
Chefs will flambé a dish, setting alight the alcohol – this will reduce the alcohol content in the food or drink.
Combustion of Alcohol
NCEA L1 Science 2013
Chem
1.3
Slide40Combustion summary
Complete combustion – plentiful supply of Oxygen (CO
2
+ H
2
O)
Alkane C
3
H
8
+ 5O
2
3CO2 + 4H2
OAlkene C3H6 + 4
1/2 O2
3CO2 + 3H2OAlcohol C2
H6O + 3 O
2 2CO2 + 3H2O
Incomplete combustion – limited supply (CO + H
2O)Alkane C3H8 + 31/2
O2 3CO + 4H
2OIncomplete combustion – very limited supply (C + H2O)
Alkane C3H8
+ 2O2 3C + 4H2O
>Balance Carbon and Hydrogen on RHS
>Add oxygen to make CO
2
/CO/C and H
2
O on RHS
>Balance Oxygen by adding number of O
2
to LHS
Slide41NCEA L1 Science 2013 Chem 1.3
Summary of reactions
Slide42NCEA L1 Science 2013 Chem
1.3Effects of Combustion products on human health and the environmentCarbon Dioxide
Increased levels of
Carbon dioxide
are linked to an enhanced greenhouse effect and global warming leading to climate change. Climate change has resulted in melting polar ice and less settled weather as well as causing different climates that is affecting animal and plant survival.
Slide43NCEA L1 Science 2013 Chem 1.3
Year 10 Science 2012
43
Carbon dioxide is a greenhouse gas and traps heat in the atmosphere. Without it and other greenhouse gases, Earth would be a frozen world
Earth’s climate in 4.5
billion-year
has
naturally
changed
between being very cold and covered in ice, or very hot. In the
recent
10,000 years the planet’s climate has become much more stable,
creating an ideal environment for humans and domestication of plants and animals.
However, over the past 50-100 years, increasing human activity (such as industry, agriculture and transportation) has begun to affect the natural climate balance
. These activities are increasing the amount of greenhouse gases in our atmosphere and causing Earth to heat up faster than ever seen before since humans have been on Earth.
Slide44NCEA L1 Science 2013 Chem 1.344Around 1750, the period of history called the
industrial revolution, humans began to burn (combust) fossil fuels and produce carbon dioxide in increasing amounts. The overall effect of human activities on the climate has been a warming influence.
According
to scientific studies, in the past 650,000 years the planet has never had so much carbon dioxide in its atmosphere as it does today, and the levels
of the gas are
continuing to rise.
Human activity is increasing the CO2 in the atmosphere and Earth is becoming a warmer place
Slide45NCEA L1 Science 2013 Chem 1.345
Human activity is accelerating climate change
Persistent human activities like driving cars,
farming and burning
coal
in combustion reactions produce greenhouse gases – mainly carbon dioxide. This gas gathers
in the atmosphere, wrap around the earth and trap the sun's
heat.
Slide46NCEA L1 Science 2013 Chem 1.346
Human activity is increasing the CO2 in the atmosphere and Earth is becoming a warmer place
The carbon dioxide and other greenhouse gases in the atmosphere act as an “insulation blanket”. With not enough greenhouse gases the heat from the Sun would reach Earth but then radiate away leaving the planet to cold. With too much greenhouse gases the heat is trapped around Earth and doesn’t escape as easily making the Earth to hot.
Slide47NCEA L1 Science 2013 Chem 1.3
Year 10 Science 2012
47
Human activity is accelerating climate change
The more greenhouse gases we
release,
the faster the world's climate heats up. This process is
called global warming
but it
also leads to climate change
because it is
increasing the amount of floods, storms, cyclones, droughts and landslips. Climate change is affecting our economy, environment and the way we live – we are already seeing the effects and need to prepare for more changes in the future.
Slide48NCEA L1 Science 2013 Chem 1.348In
New Zealand likely climate change impacts include: higher temperatures, more droughts in some areas and floods in others, and a change in the amount of rain with higher rainfall in the west and less in the east.
These changes
in climate will cause a range of effects including changing agricultural
productivity
where some species will not grow as well and other warm loving species will need to be grown, warmer winters with fewer frosts, but hotter summers causing heat stress and diseases in plants and animals, rising sea levels will effect coastal areas and glaciers
are expected to
retreat.
Human activity is accelerating climate change
Slide49NCEA L1 Science 2013 Chem 1.3
49
All
living things are made of carbon and that carbon changes from one form to another in a carbon cycle
Carbon exists in a number of forms. It is part of a gas molecule called
carbon dioxide
found
in the atmosphere which can be turned into carbon compounds in plants through
photosynthesis
. This carbon is then passed along to other living organisms when they are consumed and released back into the atmosphere during
respiration and combustion
Slide50NCEA L1 Science 2013 Chem 1.3
Year 10 Science 2012
50
All
living things are made of carbon and that carbon changes from one form to another in a carbon cycle
Natural processes of photosynthesis and respiration (blue arrows) keep the carbon dioxide levels reasonably stable in the atmosphere – and therefore the global temperature steady. Human activity such as farming, industry and burning fossil fuels (red arrows) which have a large amount of “locked up” carbon are affecting this balance and causing the levels of Carbon Dioxide to increase.
Slide51NCEA L1 Science 2013 Chem 1.3
Year 10 Science 2012
51
Carbon can be stored in the Earth in ‘carbon sinks’ such as fossil fuels, rocks and ocean sediments
Slide52NCEA L1 Science 2013 Chem 1.3
Slide53NCEA L1 Science 2013 Chem 1.3Effects of Combustion products on human health and the environmentCarbon Monoxide
Carbon Monoxide (CO) is a colourless, odourless, toxic gas that is produced during incomplete combustion when not enough oxygen is available.Carbon Monoxide stops haemoglobin in red blood cells carrying oxygen around body and so a person suffocates.
Slide54NCEA L1 Science 2013 Chem 1.3
Effects of Combustion products on human health and the environmentCarbon Monoxide
Slide55NCEA L1 Science 2013 Chem 1.3
Effects of Combustion products on human health and the environmentSoot (carbon)Soot (C) is dirty and polluting. Soot is produced during combustion when there is very limited amounts of oxygen available. Carbon particles can cause asthma in some people and even lung cancer.
Slide56NCEA L1 Science 2013 Chem 1.3
Fuels Fuels are a group of chemicals, mostly alkanes but also alkenes and alcohols, that humans use by converting the chemical energy stored in the high energy bonds between carbon and hydrogen into heat and light energy through
the process of combustion. Fuels are used
to
heat homes and include coal and oil as well as for transportation and industry using oil, petrol,
diesel and coal. Other fuels are processed into plastics.
Slide57NCEA L1 Science 2013 Chem 1.3
57
The
Earth has a fixed amount of resources that have to be managed sustainably
Sustainable
means to continue being able to do something or use something
indefinitely
. Some of our fuels on Earth are
Non-renewable
such as coal, and oil and they will be all used up eventually as the process to make more takes a very long time. Other fuels such as biofuels are
renewable
. As long as we do not take to much and replace what we use then these resources can be used for a long period of time sustainably.
Slide58NCEA L1 Science 2013 Chem 1.3
58
Biomass energy
Biomass relies on the photosynthetic ability of plants to convert solar energy into chemical energy. The chemical energy stored in plants is then broken down by
enzymes
and useful
bacteria
into
biofuels
to be used in machinery.
This type of fuel is renewable as long as the same amount of trees are planted to replace those cut down. The carbon dioxide released when burning the fuels will also be reabsorbed by the plants as they grow.
Slide59NCEA L1 Science 2013 Chem 1.3
59
Non-Renewable Energy
Non renewable
energy is energy that comes from the ground and is
able to be not replaced within a useful period of time.
Fossil fuels
are the main category of
non renewable
energy. Fossil fuels include; coal, oil and natural gas. These resources come from animals and plants that have died millions of years ago and then decomposed to create a useable source of energy for humans
.
Slide6060
Fossil Fuels - Coal
Coal
was
formed millions of years ago when plants fell into peat swamps and were buried by heavy earth and rocks. Over
millions of years,
the weight of the rocks and heat in the ground turned the plants into coal
.
Most of the world’s coal was formed 300–350 million years
ago during the
Carboniferous
period that was warm and damp, ideal for plant growth.
New Zealand coals are much younger – they were made 30–70 million years
ago and they are a less energy rich fuel. Coal is mined either underground or in large open cast mines.
Slide6161
Fossil Fuels – Oil and Gas
Oil and gas were formed
many millions of years ago from
dead sea organisms falling to the sea floor
and being covered by sediment. Over time the
sediment that covered these dead creatures was compressed
and formed rock. The carbon and hydrogen atoms that used to be
part of the dead organisms bodies reformed into fuel – the liquid form called oil and the gas form. Oil and gas are mined by drilling deep into the ground from oil rigs.
Slide6262
The
limits of fossil fuels and the unlimited energy of the sun
Fossil fuels
Renewable energy
Fossil fuels are a limited resource. Extraction and mining can be expensive and can damage the surrounding area. Carbon dioxide gas that is released upon burning the fuels are contributing to the warming of the climate. Human society has a dependence on fossil fuels for energy but needs to consider alternative renewable energy sources to replace decreasing coal, gas and oil supply. Renewable energy is sustainable and in many cases produces little or no harm to the environment. As new technology develops to collect the energy it will become cheaper.
NCEA L1 Science 2013
Chem
1.3
Slide63Production of fuels – New Zealand
FuelsDue to new Zealand’s geological history and the processes involved to create fossil fuels we do not
have
large fields of crude oil (unprocessed oil) but we do have sources of coal (but not the very black and old high energy coal) and natural gas (mostly methane).
Coal can be used directly by combusting it in power stations such as
Huntly to heat water into steam and power turbines. It is also used in homes for heating. Combusting and mining coal is very polluting and its use is becoming more limited in New Zealand. Recent disasters (pike river) in coal mining have also reflected badly on the coal mining industry.
A fully laden coal train about to leave
Seddonville
for Westport
. (1898)
Slide64NCEA L1 Science 2013 Chem 1.3
Natural gas is extracted at fields around New Zealand, mostly off the coast out at sea, and this can be further processed into methanol (an alcohol fuel). We can also produce Ethanol (an alcohol fuel) through the process of fermentation – anaerobic respiration of yeast.
Production of fuels – New Zealand
Fuels
Above:
Kupe
Gas platform in
Taranaki
Slide65NCEA L1 Science 2013
Chem 1.3Methanol from Natural gas
Producing methanol (an alcohol CH
3
OH) from Natural gas (an alkane CH
4) is a three step process.Steam reforming where methane reacts with steam CH
4
+ H
2
O → CO + 3H
2
Synthesis reaction
2H2
+ CO → CH3OH
Methanol is used to make other chemicals that are used in making paints, plastics and explosives and in methylated sprits
Water shift reaction – a reaction that adjusts the ratio of CO: H2 gas
Slide66NCEA L1 Science 2013 Chem 1.3Fermentation to produce fuel (ethanol)
Fermentation is anaerobic respiration. Enzymes in yeast turn sugar solution (eg glucose) into ethanol and carbon dioxide (in the absence of oxygen).
C
6
H
12O6 → CO2 + CH
3
CH
2
OH
Glucose carbon dioxide ethanol
Slide67NCEA L1 Science 2013 Chem 1.3Production of fuels – imported Fuels
New Zealand needs to import crude oil from other countries and then further refine it (or process it) into other types such as petrol, diesel and motor oil in order to provide fuel for our cars, trucks and industries. These processes of refining include fractional distillation to separate out the mixed length carbon chain alkanes into distinct types of fuel as well as cracking which breaks the long carbon chained alkanes into shorter, more useful fuels.
Slide68NCEA L1 Science 2013 Chem 1.3Fractional distillation of crude oil
Fractional columnCoolest at the top, gases (Carbon chains 1 – 4) collected at the top – they have the lowest boiling points which is why they don’t condense – they stay as gasesCooler as you go up, smaller molecules condense higher up as they have lower boiling points
Hottest
at bottom. Large molecules condense here as have highest boiling points
Slide69Fractional distillation of crude oil
Slide70NCEA L1 Science 2013 Chem 1.3
Petroleum Gas - Used for heating, cooking, and making plastics
-small alkanes (1 to 4 carbon atoms)
-commonly known by the names methane, ethane, propane, butane
-boiling range = less than 104 degrees Fahrenheit / 40 degrees Celsius
-often liquified under pressure to create LPG (liquified
petroleum gas)
Naphtha
- intermediate that will be further processed to make gasoline
-mix of 5 to 9 carbon atom alkanes
-boiling range = 140 to 212 degrees Fahrenheit / 60 to 100 degrees
Celsius
Gasoline
- motor fuel -liquid -mix of alkanes and cycloalkanes (5 to 12 carbon atoms)
-boiling range = 104 to 401 degrees Fahrenheit / 40 to 205 degrees Celsius * Kerosene
- fuel for jet engines and tractors; starting materials for making other products -liquid -mix of alkanes (10 to 18 carbons) and aromatics
-boiling range = 350 to 617 degrees Fahrenheit / 175 to 325 degrees Celsius *
Different hydrocarbons and their boiling points
Slide71Gas oil - used for diesel fuel and heating oil; starting material for making other products -liquid -alkanes containing 12 or more carbon atoms
-boiling range = 482 to 662 degrees Fahrenheit / 250 to 350 degrees Celsius *
Lubricating oil
- used for motor oil, grease, other lubricants
-liquid -long chain (20 to 50 carbon atoms) alkanes, cycloalkanes, aromatics
-boiling range = 572 to 700 degrees Fahrenheit / 300 to 370 degrees Celsius *
Heavy gas or fuel oil
- used for industrial fuel; starting material for other
products
-liquid
-long chain (20 to 70 carbon atoms) alkanes, cycloalkanes, aromatics
-boiling range = 700 to 1112 degrees Fahrenheit / 370 to 600 degrees Celsius * Residuals
- coke, asphalt, tar, waxes; starting material for other products -solid
-multiple-ringed compounds with 70 or more carbon atoms -boiling range = greater than 1112 degrees Fahrenheit / 600 degrees CelsiusDifferent hydrocarbons and their boiling points
Slide72NCEA L1 Science 2013 Chem 1.3Cracking of fractions
The cracking process uses heat and/or catalyst to break long less useful alkenes e.g. naptha fraction, into smaller more useful ones such as to make petrol or to make ethene
(that can be made into plastics)
Temp, pressure, catalyst
C
10
H
22
----------------------
C
8
H
18 + C
2H4 Long hydrocarbon chain alkane + alkene