C1: Carbon Chemistry
OCR GCSE in Chemistry B
Gateway Science
J264
Name…………………………………..
Form……………………….
This booklet contains a summary of the
information and concepts in the
C1 module.
You’ll need this material for your year 10
exam, and you should also refer back to it
when you’re revising for year 11. Take good
care of this booklet!
NOTE: the syllabus changed in 2011 and the letters and numbers
(C1a, C1b etc) changed. Be careful when looking at older books
and resources; they may reflect the old syllabus. The information
in this booklet is correct for the course you’re following.
C1a – MAKING CRUDE OIL USEFUL
Crude oil, coal and natural gas are all fossil fuels. Fossil fuels are finite which means they
are either no longer being made (or are being made so slowly) that they’re non-renewable
because they are being used up faster than they are formed.
The finite nature of crude oil causes a number of problems including;
•
•
•
All readily extractable resources will be used up in the future.
Finding alternatives to fossil fuels.
Conflict between making petrochemicals and fuels.
Crude oil is a mixture of many different hydrocarbons. It can be split into more useful
products called fractions by fractional distillation. It works by:
•
•
•
•
Heating the crude oil and passing it into a fractionating column which is cold at the
top and hot at the bottom.
Fractions containing mixtures of small range of hydrocarbons are obtained.
Each fraction contains a number of substances of similar size, with similar boiling
points.
Smaller fractions with lower boiling points ‘exit’ from the top end of the fractionating
column and larger fractions with higher boiling points ‘exit’ at the bottom end of the
fractionating column.
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The diagrams below show the hydrocarbon structures for propane and butane, which are
both molecules found in crude oil. The lines between the atoms represent the covalent
bonds that hold them together. These covalent bonds are very strong and are not easily
broken. They are much stronger than the intermolecular forces between the hydrocarbon
molecules and it is these intermolecular forces which are disrupted when the substance
turns from a liquid into a gas (boils).
Larger hydrocarbon chains have stronger intermolecular forces keeping the molecules
together and therefore require more energy to boil; they have higher boiling points.
Smaller hydrocarbon chains have weaker intermolecular forces and therefore require less
energy to boil; they have lower boiling points.
Propane
C3H8
Butane
C4H10
Cracking
Oil companies have lots of larger, less useful hydrocarbons and a shortage of smaller,
more useful hydrocarbons, which are in high demand, such as those used for petrol.
They solve this problem by the use of a process called cracking that converts large
alkane molecules into smaller alkane and alkene molecules. The smaller alkane
molecules can be used as fuels; the alkenes can be used to make polymers (see C1d).
The laboratory apparatus used for the cracking of liquid paraffin is shown below. It
requires a catalyst and high temperatures.
ceramic wool
+ paraffin
clamp
water
heat
aluminium
oxide beads
(catalyst)
Bunsen
valve
Environmental problems
Environmental problems caused by the use of crude oil include leakages (either from
wells or during transportation). These leaks then lead to further problems such as
damage to birds’ feathers causing death, and damage to wildlife caused by the use of
detergents to clean up the oil slicks.
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There are also a number of political issues to consider surrounding future supplies of
crude oil to the UK from politically unstable countries.
C1b – USING CARBON FUELS
There are seven things that you need to consider when choosing the best fuel. You can
remember these using TEACUPS:
T
E
A
C
U
P
S
Toxicity – how poisonous the fuel is.
Energy value – how much energy the fuel gives out.
Availability – how easy the fuel is to get hold of.
Cost – how expensive the fuel is.
Usability – how easy the fuel is to use.
Pollution – how much pollution is created by the fuel.
Storage – how easy is the fuel to store.
The amount of fossil fuels currently being burnt is increasing due to increasing world
population and growth of use in developing countries.
Burning fuels
The combustion of all fuels needs oxygen and releases useful heat energy. When
hydrocarbons are burnt in lots of oxygen, carbon dioxide and water are produced. This is
called complete combustion.
The diagram below shows how you can test these products:
The pump draws air through the apparatus as the hydrocarbon burns. The first test tube
contains blue cobalt chloride paper; this turns pink in the presence of water, confirming its
production. The second test tube contains limewater which turns cloudy as carbon dioxide
gas is bubbled through it.
The word and balanced symbol equations for the complete combustion of ethane are
shown below;
ethane + oxygen Æ carbon dioxide + water
2C2H6 + 7O2 Æ 4CO2 + 6H2O
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Incomplete Combustion
If fuel is burned without enough oxygen, incomplete combustion occurs. This forms the
poisonous gas carbon monoxide and carbon (soot).
The word equation for this reaction is shown below:
ethane + oxygen Æ carbon monoxide + carbon + water
Complete combustion is better than incomplete combustion because:
•
•
•
Less soot is produced,
More heat is produced,
Carbon monoxide is not produced.
Bunsen flames
When you heat something using a Bunsen burner, you are told to use a blue flame. This
is because the blue flame is a result of complete combustion, whereas the yellow flame is
due to incomplete combustion. The blue flame gives out more heat energy and is much
cleaner because it doesn’t produces soot like the yellow flame.
C1c – CLEAN AIR
The air around us is a mixture of different gases in different proportions. It contains;
•
•
•
•
•
21% oxygen
78% nitrogen
0.035% carbon dioxide
0.9% argon
0.07% other gases
The percentage of oxygen and carbon dioxide in the atmosphere remains constant
because of the carbon cycle. This includes combustion and respiration which both use up
oxygen and produce carbon dioxide.
The word and symbol equations for respiration are:
Glucose + oxygen Æ carbon dioxide + water
C6H12O6 + 6O2 Æ 6CO2 + 6H2O
Photosynthesis in green plants uses up carbon dioxide and produces oxygen. The word
and symbol equations for photosynthesis are:
Carbon dioxide + water Æ glucose + oxygen
6CO2 + 6H2O Æ C6H12O6 + 6O2
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The balance of carbon dioxide and oxygen in the air can be disturbed by human
influences such as:
•
•
•
Deforestation
Increasing energy consumption (which results in more fossil fuels being burned)
Population increase
The atmosphere developed into how it is today over millions of years. The key stages of
its evolution are outlined below:
•
•
•
•
•
•
Degassing of early volcanoes producing an atmosphere rich in water and carbon
dioxide.
Condensing of water vapour to form oceans.
Dissolving of carbon dioxide in ocean waters.
Relative increase of nitrogen due to its lack of reactivity.
Development of plants that photosynthesize.
Increase in oxygen levels due to photosynthesis.
Common pollutants & sources:
•
•
•
Carbon monoxide – formed by the incomplete combustion of petrol or diesel in car
engines.
Oxides of nitrogen – cause photochemical smog & acid rain – formed in the
internal combustion engine.
Sulfur dioxide – causes acid rain that kills plants and fish, and erodes stonework
and some metals – formed when sulfur impurities in fossil fuels burn.
Catalytic converters are fitted to all new car exhausts to remove carbon monoxide and
nitrogen monoxide. A catalytic convertor converts these harmful gases to nitrogen and
carbon dioxide as shown in the symbol equation below:
2CO + 2NO Æ N2 + 2CO2
C1d – MAKING POLYMERS
A hydrocarbon is a compound that is made up of hydrogen and carbon atoms only.
Alkanes are one family of hydrocarbons, they contain only single covalent bonds between
their carbon atoms. Compounds that contain only single C–C bonds are called saturated
and fit the general formula CnH2n+2
propane C3H8
C1: Carbon Chemistry 6
The covalent bond between the carbons in an alkane is made from two electrons, one
from each of the carbon atoms. The carbon atoms share this pair of electrons. The
hydrogen and carbon atoms also share an electron pair to form a covalent bond.
Alkenes are another family of hydrocarbons, they are different from alkanes as they
contain at least one double covalent bond between their carbon atoms. Hydrocarbons
that contain double C=C bonds are called unsaturated.
propene C3H6
Testing for unsaturation
You can test whether a hydrocarbon is saturated or unsaturated using bromine water,
which is made by dissolving bromine (Br2) in water. If ethane is bubbled through bromine
water no reaction will occur and the mixture will remain a clear orange/yellow. However,
unsaturated compounds will undergo an addition reaction, which causes the bromine
water to become decolourised (turn colourless). This happens because one of the double
bond breaks and the two reactants add together to form one single, colourless, dibromo
compound.
H
H
C
H
+
C
Br Br
H
colourless
orange
Br
H
H
C
C
H
H
Br
colourless
Polymerisation
Addition polymerisation involves joining monomers together by a series of addition
reactions. Each monomer molecule is unsaturated, but the polymer is saturated. This
reaction requires a high temperature or high pressure and a catalyst. The diagram below
shows the polymerisation of ethene.
Monomer
Polymer
You can see ethene on the left hand side and of the equation and poly(ethene) on the
right.
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C1e – DESIGNER POLYMERS
Polymers are used on a daily basis in a number of different roles. Examples of uses of
polymers include polystyrene cups, polyester materials, plastic containers, PVC boots
and many more.
Structure of polymers
The diagram below shows how polyethene is held together. You can see the strong
covalent bonds holding the atoms together within chains. However the intermolecular
forces between these polymer chains are weak and easily broken. This means that the
plastics have low melting points and can be stretched easily as the polymer molecules
can pass over each other.
Some plastics have bonds between the polymer molecules (cross linking bridges). These
plastics have high melting points and, because the molecules cannot slide over each
other, they can’t be stretched and are rigid.
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Nylon and Gore-Tex
Nylon is tough, lightweight and keeps liquid water and UV light out. However it doesn’t let
water vapour through it either, which means that sweat condenses inside the clothes and
the wearer can become wet and ‘clammy’.
Gore-Tex has all the properties of nylon but is also breathable. This is because it is made
up of nylon laminated with a PTFE / polyurethane membrane, which contains tiny holes.
These holes are too small for liquid water to pass through but are big enough for water
vapour to pass through. The membrane has to be combined with nylon as it is too fragile
on its own.
Sweat
Wind/ rain
Outer layer
Gore-Tex layer
Protective layer
Many polymers are non-biodegradable and so will not decay or decompose by bacterial
action. This means that they have to be placed in landfill sites, burnt or recycled. This
causes a number of environmental problems:
•
•
•
Landfill sites are filling up and it is difficult to find new ones,
When they are burnt toxic gases are produced
Recycling is difficult as there are so many different types and mixed polymers are
not very useful.
In order to overcome these issues chemists are currently developing new types of
polymers that are either biodegradable or dissolve.
C1f – COOKING AND FOOD ADDITIVES
We know that cooking food is a chemical process because a new substance is formed,
the process is irreversible and an energy change takes place. When we cook eggs or
meat the protein molecules permanently change shape (called denaturing) which
changes the texture of the food.
C1: Carbon Chemistry 9
Potatoes contain a lot of carbohydrates. They contain cellulose, which forms the cell wall
of all plants. Starch is trapped inside the potato cells. Uncooked starch is difficult to digest
and cellulose can’t be digested at all. However, cooking the potato causes the cell walls
to rupture resulting in a loss of rigid structure and a softer texture. The starch grains are
released, absorb the water, swell and spread out making them easier to digest.
Food additives
There are a number of different food additives with different functions;
• Antioxidants stop food from reacting with oxygen
• Food colours give an improved colour
• Flavour enhancers improve the flavour of the food
• Emulsifiers help oil and water to mix and not separate.
Emulsifiers are molecules that have a water loving (hydrophilic) head that bonds to water
molecules and an oil or fat loving (hydrophobic) end that bonds with oil or fat molecules.
water
oil
droplet
emulsifier molecule
Baking powder
Baking powder is used in cake mixtures in order to make the cake rise. It is able to do this
as it contains sodium hydrogencarbonate, which breaks down (decomposes) in the
baking process to produce carbon dioxide. This carbon dioxide causes the cake to rise
and leaves lots of tiny little holes.
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Sodium hydrogencarbonate Æ sodium carbonate + water + carbon dioxide
2NaHCO3
Æ Na2CO3
+
H2O
+
CO2
You can test to see if the gas released during a chemical reaction is carbon dioxide by
bubbling the gas through colourless limewater (calcium hydroxide). If the limewater turns
cloudy, then the gas is carbon dioxide.
calcium hydroxide + carbon dioxide Æ calcium carbonate + water
Ca(OH)2 + CO2 Æ CaCO3 + H2O
C1g – SMELLS
Cosmetics are either synthetic or natural depending upon their source. The organic
compounds that give perfumes their smell are called esters.
Perfumes
Perfumes need to have certain physical properties including;
• Easily evaporates so that the perfume particles can easily reach the nose.
• Non-toxic so it does not poison you.
• Does not react with water (because otherwise it would react with perspiration).
• Does not irritate the skin.
• Insoluble in water so it isn’t washed off too easily.
How easily a liquid evaporates is called volatility. In order to evaporate particles need
sufficient energy to overcome the attraction to other molecules in the liquid. Only weak
attraction exists between the particles in the liquid perfume so it is easy to overcome this
attraction.
Esters
Esters can also be used as solvents. A solution is a mixture of a solvent and a solute that
does not separate out. Ethyl ethanoate is an ester that is a non-aqueous solvent, so it
dissolves many substances that are not dissolved by water. For example nail varnish
does not dissolve in water but does dissolve in ethyl ethanoate. This is because the
attraction between water molecules is stronger than the attraction between water
molecules and particles in nail varnish. It is also because the attraction between particles
in nail varnish is stronger than the attraction between water molecules and particles in nail
varnish.
Esters are made by reacting an organic acid with an alcohol in the presence of an acid
catalyst. An example is:
acid catalyst
ethanoic acid
organic acid
+
+
ethanol
alcohol
Æ
Æ
ethyl ethanoate
ester
+
+
water
water
C1: Carbon Chemistry 11
Testing cosmetics
Cosmetics and perfumes need to be thoroughly tested before they can be sold in shops,
so that they do not cause any harm or allergic reactions. The testing of cosmetics on
animals is now banned in the EU because it doesn’t necessarily show or predict the effect
of the cosmetics on humans and therefore is unnecessarily cruel to animals.
Animal testing however is not banned for pharmaceutical products. This is so medicines
can be tested on animals and we can avoid doing unnecessary harm to humans but still
move forward with pharmaceutical developments.
In an exam, you need to be able to discuss and compare the advantages and
disadvantages of animal testing. Make sure you give clear comparisons, e.g. “animal
testing allows you to predict the effect on humans, BUT it may harm the animals”.
C1h – PAINTS AND PIGMENTS
Paints contain a number of different ingredients all with specific purposes;
• Solvent – thins the paint and makes it easier to spread.
• Binding medium – sticks the pigment in the paint to the surface
• Pigment – the substance that gives paint its colour.
Paint is a mixture called a colloid. This is where the particles are mixed and dispersed
with particles of a liquid but are not dissolved. The different component particles of the
paint do not separate out because they are scattered throughout the mixture. The
particles are also small enough so that they do not settle at the bottom.
Most paints, such as emulsions, are applied as a thin layer that dries as the solvent
evaporates. However oil paints use hydrocarbon oil as the solvent and consist of
pigments spread throughout the oil. They often contain an extra solvent that dissolves the
oil to form a solution. After the paint is applied, the solvent evaporates and the binding
medium reacts with the oxygen in the air (oxidises) to form a paint film.
Special paints
Thermochromic paint, contains thermochromic pigments that change colour when heated
or cooled. These can be used to coat a cup or kettle (to show when it is hot), or added to
acrylic paints to give even more colour changes. For example yellow acrylic paint can be
mixed with blue thermochromic paint to make green paint at room temperature but will
then turn blue when heated.
Phosphorescent pigments can glow in the dark. They are able to do this as they store
energy and then release it as light over a period of several hours. They release this light
energy whether it’s light or dark outside (they don’t ‘know’ when it’s dark) but usually the
light is so faint you can only see it in the dark. These pigments are often used in watch
faces or on road signs and are much safer than the dangerous radioactive sources that
were used in the first half of the 20th century.
C1: Carbon Chemistry 12