Carbon Chemistry

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Carbon Chemistry
(OCR Gateway)
W Richards The Weald School
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The structure of the atom
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
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Mass and atomic number
Particle Relative Mass Relative Charge
Proton 1 1
Neutron 1 0
Electron 0 -1
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Elements
If a solid, liquid or gas is made up of only one
type of atom we say it is an element. For
example, consider a tripod made up of iron
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Compounds
Compounds are different to elements. They
contain different atoms. Here are some examples
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Some simple compounds
Carbon dioxide, CO2
Water, H2O
Ethyne, C2H2
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An Introduction to Bonding
Hi. My names Johnny Chlorine. Im in Group 7,
so I have 7 electrons in my outer shell







Id quite like to have a full outer shell. To do
this I need to GAIN an electron. Who can help me?
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Bonding
Here comes one of my friends, Harry Hydrogen
Hey Johnny. Ive only got one electron. Fancy
sharing?
Now were sharing electrons. Weve formed a
covalent bond.
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Bonding
Here comes another friend, Sophie Sodium
Hey Johnny. Im in Group 1 so I have one
electron in my outer shell. Unlike Harry, this
electron is far away from the nucleus so Im
quite happy to get rid of it. Do you want it?
Okay
Ive given my electron to Jonny. This is an
ionic bond.
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Simple chemical reactions
Water
H2O
Magnesium sulphate
MgSO4
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Chemical formulae
The chemical formulae of a molecule or compound
is simply a way of showing the ratio of atoms in
it. For example
sodium chloride (NaCl)
potassium iodide (KI)
potassium nitrate (KNO3)
K
N
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Chemical formulae

• Try drawing these
• Water H2O
• Carbon dioxide CO2
• Calcium sulphate CaSO4
• Magnesium hydroxide Mg(OH)2

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Naming compounds
Rule 1 If two identical elements combine then
the name doesnt change
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Naming compounds
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Naming compounds

1. Potassium hydrogen oxygen
2. Lithium hydrogen oxygen
3. Calcium hydrogen oxygen
4. Mg(OH)2

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Naming compounds
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Balancing equations
Consider the following reaction


This equation doesnt balance there are 2
hydrogen atoms on the left hand side (the
reactants and 3 on the right hand side (the
products)
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Balancing equations
We need to balance the equation


Now the equation is balanced, and we can write it
as
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Some examples
2 2 2 3
2 2 2 2 3
2 2 2 2 2 4
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Periodic Table Introduction
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Periodic table







Horizontal rows are called PERIODS
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The Periodic Table
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg

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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
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The Chemistry of Cooking
Now consider a potato cell
Cooking a potato causes the cell wall to break
and release starch grains
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Baking Powder
Baking powder is used to make bread rise
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Testing for carbon dioxide
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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
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E numbers
If artificial additives are approved they are
given an E number
E100E199 (colours) E200E299 (preservatives)
E300E399 (antioxidants, acidity regulators)
E400E499 (thickeners, stabilizers, emulsifiers)
E500E599 (acidity regulators, anti-caking
agents) E600E699 (flavour enhancers) E900E999
(miscellaneous) E1000E1999 (additional
chemicals)
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Emulsions
Whats an emulsion?
Its a mixture of oil and water, like in salad
dressing
Paint is an emulsion. Other examples
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Emulsifiers - the details
Water
Oil
-

Emulsifier
-
-
-
-

-
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Active Packaging
Active packaging is when a product is packaged
with something that improves it, e.g.
Silica gel, to absorb water
A widget, to improve appearence and flavour
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Perfumes
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 dont react with water

A typical perfume reaction
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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
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Making a solution

• A solution forms because there are
• Weak forces of attraction between solute
  molecules
• 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.
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Fuels
Fuels are substances that can be used to release
useful amounts of energy when they burn, e.g.
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Crude Oil
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Hydrocarbons and crude oil
Crude oil is a mixture of HYDROCARBONS (compounds
made up of carbon and hydrogen). Some examples

• Longer chains mean
• Less ability to flow
• Less flammable
• Less volatile
• Higher boiling point

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Fractional distillation
Crude oil can be separated by fractional
distillation. The oil is evaporated and the
hydrocarbon chains of different lengths condense
at different temperatures
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Forces between molecules
Weak force of interaction here
Longer molecules stronger force of attraction
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Cracking
Shorter chain hydrocarbons are in greater demand
because they burn easier. They can be made from
long chain hydrocarbons by cracking
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Cracking
This is a THERMAL DECOMPOSITION reaction, with
clay used as a catalyst
Cracking can be used (as well as fractional
distillation) to extract petrol from crude oil.
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Alkanes
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 bonds, for example
Alkanes are fairly unreactive (but they do burn
well).
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General Formulae for Alkanes
Instead of circles, lets use letters
General formula for alkanes CnH2n2
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Alkenes
Alkenes are different to alkanes they contain
DOUBLE COVALENT bonds. For example
This double bond means that alkenes have the
potential to join with other molecules this
make them REACTIVE.
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General Formulae for Alkenes
General formula for alkenes CnH2n
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Monomers and Polymers
Heres 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
Step 2 Add the molecules together
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Another way of drawing it
Instead of circles, lets use letters
General formula for addition polymerisation
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Some examples
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Uses of addition polymers
Poly(ethene)
Poly(propene)
Poly(chloroethene), PVC
Poly(styrene)
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Man made fibres
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)
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Structure of Plastics
1) Some plastics have ____ intermolecular forces
between each molecule these have __ melting
points and can be ________ easily
2) Some plastics have _____ forces between each
molecule. These have ____ melting points and are
____.
Words high, low, strong, weak, stretched, rigid
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Disposal of plastics
Words recycling, greenhouse, decompose,
biodegradable, poisonous
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Choosing a fuel
Which fuel should you use?
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Burning Fuels
Lots of oxygen
Methane
Some oxygen
Little oxygen
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Endothermic and exothermic reactions
If a reaction gives out energy (e.g. it gets hot)
its an EXOTHERMIC reaction, e.g. burning
If a reaction takes in energy (e.g. it gets cold)
its an ENDOTHERMIC reaction, e.g. photosynthesis
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Burning Methane
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Breaking and making bonds
1) To burn methane you have to break all of these
bonds
2) And then you have to make these ones
Basically, the reaction is EXOTHERMIC if (2) is
greater than (1), i.e. More energy is released.
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Energy from fuels
Step 1 Calculate the energy gained by the
water Energy gained by water mass of water x
4.18 J/gC0 x change in temperature Step 2
Divide this value by the mass of the alcohol used
to find out the energy gained by the water per
gram of alcohol Energy gained per gram (answer
to Step 1) / mass of alcohol burned
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An example calculation
While doing this experiment, Gwyn got the
following results for methanol
Mass of water Start temp End temp Temp diff Start mass End mass Mass diff
100g 16 51 35 159.67 158.22 1.45
Step 1 100g x 4.18 J/gC0 x 35 14630 J Step
2 14630 / 1.45 10090 J/g