13/04/2015
Carbon Chemistry
OCR Gateway
W Richards
Fundamental concepts
Compounds
Compounds are formed
when two or more
elements are
chemically combined.
Some examples:
Methane
Sodium
chloride (salt)
Glucose
Some simple compounds…
Methane, CH4
Water, H2O
Carbon
dioxide, CO2
Key
Hydrogen
Ethyne, C2H2
Oxygen
Sulphuric
acid, H2SO4
Carbon
Sulphur
More simple compounds…
Water
SO2
Carbon dioxide
H2O
Carbon monoxide
NaHCO3
Sodium hydrogencarbonate
Na2CO3
Sulfur dioxide
CO2
Sodium carbonate
CO
Chemical formulae
The chemical formulae of a molecule or compound is simply a
way of showing the ratio of atoms in it. For example…
Na
Cl
= sodium chloride (NaCl)
K
I
= potassium iodide (KI)
O
K
N
O
O
= potassium nitrate (KNO3)
Chemical formulae
Try drawing these:
1) Water H2O
2) Carbon dioxide CO2
3) Calcium sulphate CaSO4
4) Magnesium hydroxide Mg(OH)2
Simple chemical reactions
H
Mg
O
Cl
H
Cl
Cl
Magnesium + Hydrochloric
oxide
acid
MgO
+
2HCl
Mg
H
Cl
Magnesium
chloride
+
Water
MgCl2
+
H2O
O
O
Mg
Cu
O
S
O
Cu
Mg
Mg
+
Copper
sulphate
CuSO4
O
S
O
O
Magnesium +
O H
Copper
+
Magnesium
sulphate
Cu
+
MgSO4
O
Naming compounds
Rule 1– If two identical elements combine then the
name doesn’t change
This happens with the following elements:
1) H2
4) F2
2) N2
5) Cl2
3) O2
6) Br2
These elements always go
around in pairs (diatomic
molecules). For example,
hydrogen looks like this:
Naming compounds
Rule 2 – When two elements join and one is a halogen,
oxygen or sulphur the name ends with ____ide
e.g. Magnesium + oxygen
magnesium oxide
1) Sodium + chlorine
6) KBr
2) Magnesium + fluorine
7) LiCl
3) Lithium + iodine
8) CaO
4) Chlorine + copper
9) MgS
5) Oxygen + iron
10)KF
Naming compounds
Rule 3 – When three or more elements combine and two of
them are hydrogen and oxygen the name ends with
hydroxide
e.g. Sodium + hydrogen + oxygen
Sodium hydroxide
1) Potassium + hydrogen + oxygen
2) Lithium + hydrogen + oxygen
3) Calcium + hydrogen + oxygen
4) Mg(OH)2
Naming compounds
Rule 4 – When three or more elements combine and
one of them is oxygen the ending is _____ate
e.g. Copper + sulphur + oxygen
Copper sulphate
1) Calcium + carbon + oxygen
6) AgNO3
2) Potassium + carbon + oxygen
7) H2SO4
3) Calcium + sulphur + oxygen
8) K2CO3
4) Magnesium + chlorine + oxygen
5) Calcium + oxygen + nitrogen
Balancing equations
13/04/2015
Consider the following reaction:
Sodium + water
Na
+
sodium hydroxide + hydrogen
Na
O
H
H
O
H
+
H
H
This equation doesn’t balance – there are 2 hydrogen
atoms on the left hand side (the “reactants” and 3 on
the right hand side (the “products”)
Balancing equations
13/04/2015
We need to balance the equation:
Sodium + water
sodium hydroxide + hydrogen
Na
O
H
Na
+
Na
H
O
O
H
Na
H
O
H
+
H
H
Now the equation is balanced, and we can write it as:
2Na(s) + 2H2O(l)
2NaOH(aq) + H2(g)
H
Some examples
2Mg
O2
2 MgO
Zn
+ 2 HCl
ZnCl2
2 Fe
+ 3Cl2
2 FeCl3
NaOH
CH4
Ca
+
+
HCl
+ 2 O2
NaCl
CO2
+
+
13/04/2015
H2
H 2O
+ 2H2O
+ 2 H2O
Ca(OH)2
+
+
H2SO4
Na2SO4
+ 2H2O
2 CH3OH
+ 3 O2
2 NaOH
2 CO2
+ 4H2O
H2
The structure of the atom
13/04/2015
The Ancient Greeks used to believe that
everything was made up of very small particles. I
did some experiments in 1808 that proved this
and called these particles ATOMS:
Dalton
NEUTRON –
neutral, same
mass as
proton (“1”)
PROTON –
positive, same
mass as
neutron (“1”)
ELECTRON –
negative, mass
nearly nothing
Mass and atomic number
13/04/2015
Particle
Relative Mass
Relative Charge
Proton
1
+1
Neutron
1
0
Electron
Very small
-1
MASS NUMBER = number of
protons + number of neutrons
SYMBOL
PROTON NUMBER = number of
protons (obviously)
Mass and atomic number
13/04/2015
How many protons, neutrons and electrons?
Atoms, ions and molecules
An “atom” is simply one
particle on its own in its
“normal” state, e.g. a helium
atom:
An “ion” is an atom that has
lost or gained electrons, e.g.
sodium:
A “molecule” is a combination
of atoms in a compound:
+
Na
Na
Examples of ionic molecules
Magnesium
chloride:
Mg
2+
Cl
Cl
Mg
+
-
-
Cl
Cl
MgCl2
Calcium oxide:
Ca
+
2+
O
Ca
2-
O
CaO
Bonding introduced
Cl
Hi. My name’s Johnny Chlorine.
I’m in Group 7, so I have 7
electrons in my outer shell
I’d quite like to have a full outer
shell. To do this I need to GAIN
an electron. Who can help me?
Cl
13/04/2015
Bonding
Cl
13/04/2015
Here comes one of my friends, Harry
Hydrogen
Hey Johnny. I’ve only got one
electron but it’s really close to my
nucleus so I don’t want to lose it.
Fancy sharing?
Cl
H
Now we’re both really stable.
We’ve formed a covalent bond.
H
Bonding
Here comes another friend, Sophie
Sodium
Cl
Na
Hey Johnny. I’m in Group 1 so I have
one electron in my outer shell. Unlike
Harry, this electron is far away from
the nucleus so I’m quite happy to get
rid of it. Do you want it?
Okay
+
Cl
13/04/2015
Na
Now we’ve both got full outer shells
and we’ve both gained a charge.
We’re both called IONS and we’ve
formed an IONIC bond.
C1a – Making Crude Oil useful
Fuels
A “fuel” is something that can be burned to release heat and
light energy. The main examples are:
Coal, oil and gas are called “fossil fuels”. In
other words, they were made from fossils.
Hydrocarbons and crude oil
13/04/2015
Crude oil is a mixture of HYDROCARBONS
(compounds made up of carbon and hydrogen).
Some examples:
H
C
C
H
H
H
Ethane
H
H
H
H
H
C
C
C
C
H
H
H
H
Butane
H
Increasing length
H
H
Longer chains mean…
1. Less ability to flow
2. Less flammable
3. Less volatile
4. Higher boiling point
Distillation revision
13/04/2015
This apparatus can be used to
separate water and ethanol
because they have different
_____ ______. The ______
will evaporate first, turn back
into a _______ in the
condenser and collect in the
_______. The water remains
in the round flask, as long as
the _______ does not
exceed water’s boiling point.
This method can be used to
separate crude oil.
Words – temperature, boiling points, ethanol, beaker, liquid
Forces between molecules
Weak force of interaction here
Longer molecules =
stronger force of
attraction
Fractional distillation
13/04/2015
Crude oil can be separated by fractional distillation. The oil is evaporated
and the hydrocarbon chains of different lengths condense at different
temperatures due to the different intermolecular forces between each
molecule:
Fractions with
low boiling
points condense
at the top
Fractions with
high boiling
points condense
at the bottom
Crude Oil
13/04/2015
Using Crude Oil
Benefits
Drawbacks
Getting oil from
unstable countries?
Cheap to
extract
Wide range of
uses as fuel
Used to make
plastics
13/04/2015
Crude Oil
It’s
going to
run out
Burning
fossil fuels
causes
pollution
It takes
millions of
years to
form
Cracking
13/04/2015
Shorter chain hydrocarbons are in greater demand because
they burn easier. They can be made from long chain
hydrocarbons by “cracking”:
Butane
Ethane
For example, this bond
can be “cracked” to
give these:
Ethene
Cracking
Gaseous
hydrocarbon
Long chain
hydrocarbon
Heated
catalyst
13/04/2015
Liquid
hydrocarbon
This is a THERMAL DECOMPOSITION reaction,
with clay used as a catalyst
Cracking is used to produce plastics such as polymers and polyethanes. The
waste products from this reaction include carbon dioxide, sulfur dioxide
and water vapour. There are three main environmental problems here:
1) Carbon dioxide causes the _________ effect
2) Sulfur dioxide causes _____ _____
3) Plastics are not _____________
C1b – Using Carbon Fuels
Choosing a fuel
Does it create
pollution?
How much energy
does it release?
Which fuel should
you use?
How much does
it cost?
Is it toxic?
Is it easy to use,
store and transport?
Burning Fuels – “Combustion”
Lots of
oxygen:
H
H
H
O
C
O
H
Methane
+
O
O
Oxygen
C
H
O
H
O
Carbon
dioxide
+
O
O
H
H
Water
What would a balanced symbol equation for this reaction look
like?
Incomplete Combustion
Incomplete combustion is when a fuel is burned
without having a plentiful supply of oxygen, e.g.
when the Bunsen’s air hole is closed:
H
Some
oxygen:
H
O
C
H
H
H
H
O
H
H
Methane
Little
oxygen:
H
H
O
C
+
H
H
Methane
+
O
C
O
C
O
O
Oxygen
O
C
O
O
Oxygen
Carbon
monoxide
+
C
Carbon
Balanced symbol equations?
+
H
O
H
O
H
O
H
O
H
H
H
H
Water
H
O
H
O
Water
H
H
Incomplete Combustion
As well as producing carbon monoxide, incomplete combustion
can also produce soot:
Little
oxygen:
H
H
H
O
C
H
Methane
+
O
Oxygen
C
Carbon
“Soot”
+
H
O
H
O
Water
H
H
C1c – Clean Air
The Earth’s Atmosphere
13/04/2015
For the last 200 million years the atmosphere has remained roughly the
same – it contains 78% nitrogen, 21% oxygen, 1% noble gases and about
0.03% CO2
Carbon dioxide, water vapour
Oxygen
Nitrogen
Noble gases
The Carbon Cycle
CO2 in air
5. Burning
fossil fuels
also releases
CO2
4. Animals
release CO2
through
respiration
13/04/2015
2. Plants and algae
release CO2 through
respiration
1. CO2 is taken in
by plants and
algae for
photosynthesis
and turned into
carbohydrates,
fats and proteins
3. The carbon taken in
by plants is then eaten
by animals and the
animals that eat them
13/04/2015
Evolution of the Earth’s Atmosphere
Carbon
dioxide
4 Billion years
Methane
Ammonia
Oxygen
Nitrogen
Others
Present day
atmosphere contains
78% nitrogen, 21%
oxygen, 1% noble
gases and about
0.03% CO2
3 Billion years
2 Billion years
1 Billion years
Present day
13/04/2015
Evolution of the Earth’s Atmosphere
Volcanic activity
releases CO2, methane,
ammonia and water
vapour into the
atmosphere. The water
vapour condenses to
form oceans.
4 Billion years
3 Billion years
Some of the oxygen is
converted into ozone.
The ozone layer blocks
out harmful ultra-violet
rays which allows for the
development of new life.
2 Billion years
1 Billion years
Green plants evolve which take in CO2 and
give out oxygen. Carbon from CO2
becomes locked up in sedimentary rocks as
carbonates and fossil fuels. Methane and
ammonia react with the oxygen and
nitrogen is released.
Present day
Population and Pollution
The human population is
growing exponentially,
particularly in countries like
China and India:
Population
Time
This has a number of effects on the environment:
Farming –
less land available
for crops
Waste –
more waste needs
to be disposed of
Bigger
population
means…
Resources –
more resources
needed, e.g.
deforestation
Pollution –
More phosphates,
nitrates, CO2 and SO2
Pollution
What causes pollution?
Carbon monoxide is a
poisonous gas formed by
incomplete combustion.
Sulfur dioxide causes acid rain
that kills aquatic life and
damages buildings and metals.
It’s caused when fuels
containing sulfur are burned.
Oxides of nitrogen can cause
photochemical smog and acid rain,
and are formed in internal
combustion engines
Reducing Pollution from vehicles
A number of suggestions:
1) Buy a new, smaller, cleaner car
2) Buy a “hybrid” car
3) Convert your car to run on biodiesel
4) Make sure your car has a catalytic converter:
Carbon monoxide + oxygen
2CO + 2NO
5) Use the train or a bus!
carbon dioxide
N2 + 2CO2
C1d – Making Polymers
Hydrocarbons revision
13/04/2015
Crude oil is a mixture of HYDROCARBONS
(compounds made up of carbon and hydrogen).
Some examples:
H
C
C
H
H
H
Ethane
H
H
H
H
H
C
C
C
C
H
H
H
H
Butane
H
Increasing length
H
H
Longer chains mean…
1. Less ability to flow
2. Less flammable
3. Less volatile
4. Higher boiling point
Alkanes
13/04/2015
Alkanes are SATURATED HYDROCARBONS. What does this
mean?
HYDROCARBONS are molecules that are made up of
hydrogen and carbon atoms
SATURATED means that all of these atoms are held
together by single COVALENT bonds, for example:
H
H
H
C
C
H
H
Ethane
H
H
H
H
H
H
C
C
C
C
H
H
H
H
H
Butane
Alkanes are fairly unreactive (but they do burn well). The
general formula for an alkane is CnH2n+2
General Formulae for Alkanes
13/04/2015
Instead of circles, let’s use letters…
H
H
C
H
H
H
Methane (n=1)
H
H
H
H
C
C
C
H
H
H
Propane (n=3)
H
H
C
C
H
H
H
Ethane (n=2)
H
H
H
H
H
H
C
C
C
C
H
H
H
H
Butane (n=4)
General formula for alkanes = CnH2n+2
H
Alkenes
13/04/2015
Ethane
Ethene
Butane
Butene
ALKENES
ALKANES
Alkenes are different to alkanes; they contain DOUBLE
COVALENT bonds (a bond that has two shared electrons). For
example:
This double bond means that alkenes have the potential to join
with other molecules – this make them REACTIVE. Alkenes
turn bromine water colourless.
Testing for alkenes
Bromine
water
Oil
Bromine goes
colourless
13/04/2015
This is an “addition”
reaction where the
colour change is
caused by the
formation of a
colourless dibromo
compound.
General Formulae for Alkenes
13/04/2015
H
H
H
C
C
H
Ethene (n=2)
H
H
H
H
C
C
C
H
H
H
H
H
H
C
C
C
C
H
H
H
Propene (n=3)
Butene (n=4)
General formula for alkenes = CnH2n
H
Monomers and Polymers
13/04/2015
H
H
C
C
H
H
Ethene
Here’s ethene again. Ethene is called a
MONOMER because it is just one small
molecule. We can use ethene to make
plastics…
Step 1: Break the double bond
(this often requires high
pressure and a catalyst)
Step 2: Add
the molecules
together:
This molecule is called POLYETHENE,
and the process that made it is called
POLYMERISATION
Another way of drawing it…
13/04/2015
Instead of circles, let’s use letters…
H
H
C
C
H
H
H
C
H
C
H
Ethene
H
Ethene
H
H
H
H
C
C
C
C
H
H
H
H
Poly(e)thene
General formula for addition polymerisation:
n
C
C
C
C
n
e.g.
n
H
CH3
H
CH3
C
C
C
C
H
H
H
H
n
Some examples
n
n
n
13/04/2015
H
H
H
H
C
C
C
C
H
H
H
H
H
H
H
H
C
C
C
C
Cl
H
Cl
H
H
H
H
H
Propene –
C
C
C
C
Polypropene
CH3 H
CH3 H
Ethene –
n
polyethene
Vinylchloride –
n
n
Polyvinylchloride
(PVC)
C1e – Designer Polymers
Uses of addition polymers
13/04/2015
Poly(ethene)
Poly(propene)
What properties
would these
polymers have?
Poly(styrene)
Poly(chloroethene), PVC
Structure of Plastics
1) Some plastics have ____
intermolecular forces between
each molecule – these have __
melting points and can be
______ easily as the molecules
_____ over each other.
2) Some plastics have _____
forces between each
molecule. These have ____
melting points and are ____.
Words – high, low, strong, weak, stretched, rigid, slide
Outdoor Clothing
I love doing outdoor sports. I’d
like to wear clothing that is tough
but also lets my sweat out. What
should I wear?
Nylon and Gore-Tex
Nylon – lightweight, tough,
waterproof, blocks UV
Gore-tex – nylon coated with
PTFE – this means that it can
allow perspiration to escape
but rain cannot get in (it can
“breathe”)
Gore-Tex
Gore-tex is a material made from nylon laminated with the
polymer PTFE and its invention has been of great use in the
world of outdoor sports. Here’s how it works:
Outer fabric
Gore-tex
Inner fabric
Sweat
Basically, the holes in
the material are too
small for water drops to
pass through but big
enough for sweat
vapour. On its own, the
membrane is too fragile
so it is combined with
nylon.
Disposal of plastics
1) Landfill sites - most plastics do not
_________ which means that landfill sites
are quickly filled up. Research is being
carried out on __________ plastics.
2) Burning – this releases carbon
dioxide which causes the
________ effect, as well as
other ________ gases.
3) _______ – the best option, but
difficult because of the different
types of plastic
Words – recycling, greenhouse,
decompose, biodegradable, poisonous
Biodegradable carrier bags
13/04/2015
This carrier bag has been made with flax fibre from
industrial waste.
C1f – Cooking and Food Additives
The Chemistry of Cooking
The process of cooking food causes some chemicals to turn
into others (i.e. a chemical change) and these are irreversible.
For example, consider a protein molecule:
“Denatured”
The Chemistry of Cooking
Now consider a potato cell:
Cooking a potato
causes the cell wall
to break, leading to a
softer texture.
Starch grains also
swell up and spread
out.
Artificial Additives
Why do we use additives?
Some examples:
Additive
Interesting information
Flavour enhancers
Can include traditional ingredients like salt, vinegar etc.
Monosodium glutamate is often used in Chinese foods (its
found in soy sauce)
Colour enhancers
Processing food often results in colour loss so colour
enhancers are used. Could be natural like carotenes or
artificial like tartrazine
Preservatives
Can include vinegar and sugar. Artificial preservatives are
used to stop microbes growing and antioxidants stop fats
going off
Vitamins and minerals
Can be used to replace those lost during cooking
E numbers
If artificial additives are “approved” they are given an E
number:
E100–E199 (colours)
E200–E299 (preservatives)
E300–E399 (antioxidants, acidity regulators)
E400–E499 (thickeners, stabilizers, emulsifiers)
E500–E599 (acidity regulators, anti-caking agents)
E600–E699 (flavour enhancers)
E900–E999 (miscellaneous)
E1000–E1999 (additional chemicals)
Emulsions
13/04/2015
What’s an emulsion?
It’s a mixture of oil and
water, like in salad dressing…
Paint is an emulsion. Other examples:
Milk
Cream
Butterfat
Watery liquid
Butter
Why use emulsions?
13/04/2015
Emulsions can have varying textures and this makes them
useful. Some examples:
Different
thicknesses
of cream
Paint and
mayonnaise
Emulsifiers
13/04/2015
An emulsifier is an additive that will stop oil
and water from seperating, like in mayonnaise.
How they work:
I don’t want to
mix with you!
Water
I’m an emulsifier – I’ll
sort this out with my
hydrophobic end and
my hydrophilic end!
Oil
The water and oil drops become “coated” and insulated from
one another, which prevents them from seperating.
Uses of emulsifiers in food
13/04/2015
Emulsifiers are used:
1) In bread, to stop large _____ developing when it bakes
2) In low fat spreads, to allow the oil and water to be _____
3) In ice cream and spray cream, to ______ the foam
4) In sponge cakes, to make tiny pockets of ____
5) In chocolate, to stop melted chocolate forming _______
Words – crystals, air, holes, mixed, stabilise
Baking Powder
Baking powder is used to make bread rise:
Sodium hydrogen carbonate
2 NaHCO3(s)
sodium carbonate + water + carbon dioxide
Na2CO3(s) + H20(g) + CO2(g)
Gas
Testing for
carbon dioxide:
Limewater
Limewater turns
milky/cloudy
C1g – Smells
Perfumes
Perfumes are synthetically made from chemicals called
“esters”. Here are some facts about perfumes. Why are
these things important?
1) Perfumes are non-toxic
2) They are non-irritants
3) They evaporate easily
4) They do not dissolve in water
5) They don’t react with water
A typical perfume reaction:
Ethanol + ethanoic acid
C2H5OH
+
CH3COOH
ethyl ethanoate + water
C2H5OOCCH3 + H2O
Solutions revision
If a substance CAN be dissolved it is called __________
If a substance CANNOT be dissolved it is called _________
Words – soluble, solute, solvent, solution, insoluble
Solubility words
Something that CAN dissolve is described as being…
Solute
How much of something that can be dissolved is
called…
Solution
Something that CANNOT be dissolved is described
as being…
Solvent
A solution that CAN’T dissolve anything else is…
Soluble
The solid that will be dissolved is the…
The mixture of solute and solvent is called the…
The liquid that the solute will be dissolved into is
the…
Insoluble
Saturated
Solubility
Making a solution
A solution forms because there
are:
1) Weak forces of attraction
between solute molecules
2) Strong forces of attraction
between solute and solvent
molecule
For example, nail varnish remover
works because the nail varnish
remover molecules are attracted
to the nail varnish molecules with
a stronger attraction than water
molecules are. Esters can be
used as solvents.
Cosmetics
I think that the testing of cosmetics
should be allowed.
No way! I totally
disagree.
The testing of cosmetics on animals is currently banned in the
EU. Who do you agree with and why?
C1h – Paints and Pigments
Paint
Paint is an example of a “colloid” – a mixture of
one or more substances in a liquid but which are
not dissolved. The molecules have a large surface
area:volume ratio and, as such, they have a large
surface tension and are difficult to separate.
“Ingredients” in paint
Function
Solvent
Gives the paint its colour
Pigment
Sticks the pigment to the surface
Binding medium
Thins the paint, making it easier
to spread
Water based vs Oil based
“Water-based
paints”
“Oil-based paints”
In water-based paints the paint dries when the _______
evaporates, causing them to dry in around one ______. In oilbased paints the solvent has to ________ and then the oil is
_______ by oxygen in the air, which takes longer and paint
brushes have to be cleaned with ____ ___ rather than water.
Words – white spirit, evaporate, water, hour, oxidised
Thermochromic Paint
Thermochromic
paint is paint
that changes
colour when
heated. Some
uses:
Acrylic paints can be added to
thermochromic paint to give it an even
wider range of colours.
Here’s a strange use of this paint:
Phosphorescent Paint
Phosphorescent paint is paint that contains pigments that can
glow in the dark. They do this by “storing” energy and then
release it over time:
The original “glow-in-the-dark” paint contained radioactive
materials so this paint is much safer!