Module: Chemistry 1

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Module Chemistry 1
Carbon Chemistry
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The units in this module are
C1a Cooking C1b Food Additives C1c
Smells C1d Making crude oil useful C1e Making
Polymers C1f Designer Polymers C1g Using
Carbon Fuels C1h - Energy
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C1a - Cooking

• Why we cook foods
• Methods of cooking
• Cooking proteins
• Raising agents

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Why do we cook foods?

• We cook foods for a number of reasons. Some of
  them are
• To kill harmful microbes that may cause food
  poisoning
• To make the food easier to digest
• To improve the flavour of the food
• To improve the texture of the food

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How can we cook foods?
There are several ways to cook foods.
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Cooking Proteins
Eggs are a good source of proteins. We know it is
a chemical change because the appearance changes.
When you heat up proteins, the molecule changes
shape. We say is has been denatured.
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Raising Agents
When we make a cake it is important it rises. We
add a raising agent.
Baking powder is a raising agent which contains
sodium hydrogen carbonate.
When it is heated it decomposes (breaks down)
Sodium Hydrogen ? Sodium Water
Carbon Carbonate Carbonate
Dioxide
2 NaHCO3 ? Na2CO3 H2O
CO2
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C1b - Food Additives

• Types of food additives
• E-numbers
• Emulsifiers and Antioxidants
• Active packaging

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Types of Additives
Food additives are chemicals added to food to
improve or enhance it.
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E-Numbers
Some additives have been approved for use in the
EU. These additives have E-numbers. The E-number
tells us what the additive is used for.
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Emulsifiers
Oil and water do not mix
Emulsifiers keep them mixed together in
mayonnaise.
An emulsifier molecule has two parts.
The hydrophilic head bonds to water
molecules. The hydrophobic tail bonds to the oil
molecules. This prevents oils molecules from
joining together.
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Active Packaging
Active packaging can be used to improve the
safety or quality of food.

• Examples
• Wrapping in plastic film keeps out oxygen and
  water which keeps the food crisp
• Some packaging removes water to stop food inside
  going off

Antioxidants are added to some foods or packaging
to stop them reacting with oxygen.
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C1c - Smells

• Esters
• Making esters
• Properties of perfumes
• Solvents

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Esters
Esters are a group of chemicals that provide
scents.
They can occur naturally or can be made
synthetically
Esters can be used in foods like sweets
They can also be used in perfumes
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Making Esters
Esters can be made by reacting an organic acid
with an alcohol. It produces an ester and water.
A drop of concentrated sulphuric acid acts as a
catalyst.
Organic acid Alcohol ? Ester
Water Methanoic acid Ethanol ?
Ethyl Methanoate Water
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Properties of Perfumes
Perfumes need certain properties if they are to
be used.
We can smell perfumes because they evaporate when
put on the skin. This is because the skin is
warm.
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Solvents
Esters can be used as solvents Ethyl ethanoate
can be used as nail varnish remover
Nail varnish in insoluble in water so water
cannot be used to take off varnish. A nail
varnish remover must be used.
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C1d - Making Crude Oil Useful

• Separating crude oil
• Properties of fractions
• Cracking
• Problems with crude oil

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Separating Crude Oil
Crude oil is a mixture of hydrocarbons.
Hydrocarbons contain hydrogen atoms and carbon
atoms.
The crude oil can be split into more useful
products by fractional distillation.
Vapour enters at the bottom of the tower. As it
passes up the tower, it cools. Fractions with
high boiling points condense and are collected at
the bottom. Fractions with low boiling points
condense and are collected at the top.
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Properties of Fractions
Bigger molecules have higher boiling points
Bigger molecules are more viscous
Bigger molecules are less flammable
Hydrocarbon molecules in fractions are held
together by forces of attraction called
intermolecular forces.
The stronger these forces are, the higher the
boiling point.
Bigger molecules have stronger intermolecular
forces.
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Cracking
The fractions that are used as fuels are in much
higher demand.
Oil companies can break large molecules into more
useful, smaller molecules.
This is called cracking.
Cracking is a thermal decomposition reaction and
requires heat and a catalyst.
Cracking also converts large alkane molecules
into smaller alkane molecules and an alkene
molecule.
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Problems with Crude Oil
Crude oil is a very useful chemical. However,
there are lots of problems with it.
Environmental problems Oil spills can pollute the
seas, harm wildlife when they are coated with oil
and beaches can be damages.
Political problems Countries can argue and begin
wars over who owns the oil.
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C1e - Making Polymers

• Alkanes
• Alkenes
• Polymerisation
• Polymerisation diagrams

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Alkanes
Alkanes are a group of hydrocarbons that contain
only single covalent bonds. Known as saturated
hydrocarbons.
Alkanes have the general formula, CnH2n2
Each carbon must have 4 bonds Each hydrogen must
have 1 bond
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Alkenes
Alkenes are a group of hydrocarbons that contain
one or more double covalent bonds. Known as
unsaturated hydrocarbons.
Alkenes have the general formula, CnH2n
We can distinguish between alkanes and alkenes
using bromine water.
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Polymerisation
Polymers are long chained molecules. The basic
unit in a polymer is called a monomer.
ethene ethene ethene ? Poly (ethene)
single units ? many units
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Polymerisation Diagrams
We can show polymerisation by diagrams.
The double bond in the monomer splits open.
The double bond has become single bond The same
groups are attached to the carbon atoms.
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C1f - Designer Polymers

• Uses of polymers
• Gore-Tex
• Disposal of polymers 1
• Disposal of polymers 2

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Uses of Polymers
Polymers have lots of different uses.
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Gore-Tex
Nylon has been used in clothing because it is
tough, lightweight and is waterproof. However, it
does not let water vapour out so sweat cannot
escape.
Gore-Tex has a membrane layer attached to
nylon. Gore-Tex has all the advantages of nylon
but it is also breathable. This means it lets
water vapour out.
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Disposal of Polymers 1
Polymers are non-biodegradable. There are
different methods of disposing of polymers.
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Disposal of Polymers 2
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C1g - Using Carbon Fuels

• Choosing a fuel
• Complete combustion
• Incomplete combustion

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Choosing a Fuel
When you are choosing a fuel there are several
things you need to consider. Remember TEACUPS
T ? toxicity, how poisonous is the fuel E ?
energy value, how much energy does it give A ?
availability, how easy is it to get C ? cost, how
expensive is it U ? usability, how easy is it to
use P ? pollution, does it produce harmful
gases S ? storage, how easy is it to store
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Complete Combustion
Burning of fuels requires oxygen. If there is
plenty of oxygen we get complete combustion.
Fuel Oxygen ? Carbon Dioxide Water
The limewater turns cloudy proving carbon dioxide
is made. A colourless liquid collects which boils
at 100ºC proving it is water.
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Incomplete Combustion
If there is not enough oxygen present during
combustion, then incomplete combustion takes
place.
Fuel Oxygen ? Carbon Monoxide Carbon
Water
Incomplete combustion produce less heat, more
soot and poisonous carbon monoxide.
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C1h - Energy

• Exothermic and Endothermic Reactions
• Bond calculations
• Energy from fuels
• Energy per gram

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Exothermic and Endothermic Reactions
Chemical reactions involve a transfer of energy.
Exothermic reactions give out heat energy. The
temperature increases during an exothermic
reaction. Burning is a type of exothermic
reaction.
Endothermic reactions take in heat energy. The
temperature decreases during an exothermic
reaction.
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Bond Calculations
Each bond requires a specific amount of energy to
break it. When a bond is made, it releases a
specific amount of energy.
We can work out an overall energy change
by Overall change bonds broken bonds made
4 x CH 4 x 413 1652 2 x C O 2 x 805
1610 1 x O O 1 x 498 498 4 x O H 4 x
464 1856
Overall change 2150 3466 - 1316 Joules
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Energy from Fuels
We can compare the energy given out by different
fuels using a calorimeter.
Energy mass x specific heat x temp rise
Sample results 100g water heated by
ethanol Start temp 20ºC End temp 32ºC Mass
of lamp at start 105.57g Mass of lamp at end
103.47g
Energy 100 x 4.2 x 12 5040 Joules
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Energy per Gram
A useful comparison of the energy value of fuels
is the energy given out per gram.
Energy per gram energy (J)
mass of fuel
burned (g)
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