 No Brain Too Small  CHEMISTRY 
CHEMISTRY AS 90932
Demonstrate understanding of aspects of carbon chemistry
Level 1, 4 Credits
This achievement standard involves demonstrating understanding of the structure, properties, production,
uses, importance and effects of carbon and its chemistry.
Structure: Names of carbon compounds using systematic nomenclature
Alkanes: Have the general formula CnH2n+2. At room temperature C1 – C4 are gases, C5 – C8 are liquids.
They are saturated hydrocarbons – contain only single C-C bonds.
Each one is a
bigger than the previous one.
C2H6 is a molecular formula (tells you the type and number of each atom).
formula (tells you how the atoms are bonded to each other).
is a structural
methane
ethane
propane
butane
CH4
C2H6
C3H8
C4H10
H
H
C
H
H
H
H
H
C
C
H
H
H
H
H
H
H
C
C
C
H
H
H
H
H
H
H
H
H
C
C
C
C
H
H
H
H
pentane
hexane
heptane
octane
C5H12
C6H14
C7H16
C8H18
H
H
H
H
H
H
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
C
C
C
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H C
C
C
C
C
C
C H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H C
C
C
C
C
C
C
C H
H
H
H
H
H
H
H
H
Alkenes: Have the general formula CnH2n.
ethene
propene
Ethene and propene are both gases at room
temperature. They are unsaturated hydrocarbons
– contain a C=C double bond.
C2H4
C3H6
H
H
C
H
H
C
H
C
H
C
H
H
H
C
C
C
H
H
H
H
H
H
H
H
C
C
C
C
H
H
H
H
H
H
H
H
H
H C
C
C
C
C
C
C H
H
H
H
H
H
H
H
H
H
methanol
ethanol
CH3OH
C2H5OH
H
H
H
H
Alcohols:
Have the general formula CnH2n+1OH.
H
Contain the –OH group, the alcohol group. Both
methanol and ethanol are liquids at room
temperature.
H
H
C
H
H
H
H
H
H
H
H
H
H
H
H C
C
C
C
C
C
C
C H
H
H
H
H
H
H
H
H
H
C
H
O
H
H
H
H
C
C
H
H
O
H
 No Brain Too Small  CHEMISTRY 
Covalent bonding between atoms:
Covalent bonds are formed by atoms sharing electrons to form molecules. One single covalent bond is a
sharing of one pair of electrons, two pairs of shared electrons between the same two atoms gives a double
bond and it is possible for two atoms to share three pairs of electrons and give a triple bond.
Single bond
H
H
Triple bond (won’t be examined
in this AS)
Double bond
H
H
C
C
H
H
H
H
H
C
C
H
H
H
H
H
H
C
C
H
C
C
H
H
H
H
H
C
C
H
H
C
C
H
A carbon and four hydrogen atoms all achieve stable structures by sharing their single unpaired electron as
in the diagram.
Covalent bond
H
H
C
H
Covalent bond
H
H
H
C
H
H
The fact that this has been drawn with electrons marked as crosses and dots is simply to show where all
the electrons come from. In reality there is no difference between them.
The atoms are joined by covalent bonds. The reason that the atoms stick together is that the shared pair of
electrons is attracted to the nucleus of both atoms.
(The atoms aren’t really “sharing” electrons as much as they are “fighting over” them. They are both trying
to attract the same electrons but neither one can actually take them away from the other. This creates a
situation in which both atoms are “stuck together”).
Properties

H
H
Solubility in water
The alkanes are insoluble in water. They are immiscible forming two separate layers; this is
because there are no attractive forces between the water and the hydrocarbon molecules
to allow solubility. The alkane is less dense than water.
The alcohols methanol and ethanol are soluble in water. They are soluble (miscible) in
water because there are attractive molecules between the alcohol and water.
 No Brain Too Small  CHEMISTRY 
H
H
C
H

H
H
O
H
H
O
O
C
H
H
H
Trends in melting and/or boiling points
Melting point is the temperature at which a substances changes from a solid to a liquid. Boiling point
is the temperature at which a substances changes from a liquid to a gas.
Temperature (oC)
As the number of carbon atoms in the alkane molecules increases, the mass of the molecules
increases and the molecules get bigger. As the size of the molecule increases, the temperature of the
boiling point increases. This is because the molecules are getting bigger and the attractive forces
between them are also getting bigger. This means more energy is required to break the
intermolecular bonds. This means that more energy is requires to free up particles in the solid state
(melting) or for particles to escape from the liquid state (boiling). This factor causes the
melting/boiling points to rise.
Boiling points
Melting points
Number of carbon atoms

Complete and incomplete combustion reactions
Incomplete combustion means there is not enough oxygen (insufficient percentage) present in the
air for all of the carbon atoms in the carbon compound to turn into carbon dioxide. Some or all of it
turns into carbon monoxide or carbon particles (soot). The hydrogen atoms react with oxygen to
form water. The carbon compounds burn with a yellow sooty flame.
Complete combustion requires plenty of oxygen. Complete combustion has an almost invisible
flame. All the carbon atoms react with oxygen to form carbon dioxide. The hydrogen atoms here also
react with oxygen to form water.
Energy is released in combustion. Complete combustion is a more efficient producer of energy than
incomplete combustion.

Effects of combustion products on human health and the environment.
Carbon dioxide gas is a major greenhouse gas. It contributes to the greenhouse effect. Greenhouse
gases absorb some of the heat from the sun and trap it so that the earth is warmed up. Increasing
amounts of this have added to the greenhouse effect and is known as global warming. This may
cause increases in melting of polar ice caps (which will cause flooding), increased ocean / land
temperatures, retreat of glaciers, change in migration and breeding of species, new growth and
flowering patterns of plants, extreme weather events, decreased agricultural yields etc.
 No Brain Too Small  CHEMISTRY 
Carbon monoxide gas, CO,is a dangerous gas as it is colourless and odourless and toxic. It combines
with haemoglobin in the blood, forming a stable compound with haemoglobin, thus preventing
oxygen from being carried to the parts of the body that need it. The person dies by suffocation.
Carbon particles, C, produced can affect the lungs if breathed in, and can cause respiratory problems
including asthma and even lung cancer. Carbon particles can scatter solar radiation. Large amounts of
carbon can act as a blanket, blocking solar radiation, reducing efficiency of photosynthesis.

Polymerisation reactions; polymers from ethene and propene
Polythene: In a chemical reaction numerous small ethene molecules are joined together. The ethene
molecule contains a double bond. The double bond breaks and a single covalent bond formed
between these carbon atoms and between carbon atoms of neighbouring molecules, forming long
carbon chains. This is an addition polymerisation reaction. The conditions required include high
temperature, pressure and the presence of a catalyst.
Uses of ethene are………………….
Polypropene: Many small propene molecules are joined together to form long-chain molecules. The
covalent double bond between each carbon atom in the propene molecule is broken and a single
covalent bond formed between these carbon atoms and between carbon atoms of neighbouring
molecules, forming long carbon chains which are the forms of the polypropene molecule. The
chemical reaction requires heat, high pressure and a catalyst.
Uses of polypropene are linked to properties such as low chemical reactivity (eg with air, water and
living organisms), insolubility in water, ability to be moulded or extruded into a wide range of shapes
with moderate heating, heat and electrical insulator. Being recyclable, it can be reshaped and use for
garden chairs, bins etc.

Fractional distillation of crude oil
Crude oil consists of a mixture of hydrocarbon molecules of different sizes. Hydrocarbons of different
molecular masses have different boiling points. Larger molecules have higher boiling points. Crude oil
is heated and turned into a vapour to enter the fractionating tower.
When the vapour enters the tower, the larger, heavier hydrocarbons with the higher boiling points
condense into liquids lower down in the tower, while the smaller, lighter hydrocarbons with the
lower boiling points rise up the tower and condense back into a liquid at the lower temperatures
near the top of the tower. The smallest hydrocarbons (C1 – C4) remain gases at room temperature.
The temperature at which a specific hydrocarbon condenses is related to its molecular mass,
particularly the number of carbon atoms. The lower / higher its molecular mass is, the lower / higher
the temperature at which it will condense. This determines where on the tower the particular
fraction is collected.

Cracking of fractions
 No Brain Too Small  CHEMISTRY 

Fermentation:
Fermentation is an enzyme - catalysed chemical reaction in which glucose molecules are converted
into ethanol and carbon dioxide molecules in anaerobic conditions (without oxygen) at room
temperature.
Equation: C6H12O6  2CH3CH2OH + 2CO2

Methanol from natural gas:
Uses and importance of alkanes, alkenes and alcohols

Fuels (alkanes and alcohols)
Organic compounds are used as fuels because they burn (combust) easily and produce large amounts
of energy. Complete combustion occurs when sufficient oxygen is present for the compound to form
carbon dioxide and water.
In incomplete combustion, less oxygen is available so some soot (carbon) or carbon monoxide is
formed.
Incomplete combustion produces carbon monoxide and soot as products. Soot can cause irritation
of the lungs – respiratory problems (bronchitis, asthma etc). Carbon monoxide can cause decrease in
oxygen in blood, leading to possible brain damage and death (due to binding with haemoglobin in
red blood cells, so carbon monoxide rather than oxygen is carried around the body).

Polymers (alkenes)
Alkenes because of their C=C double bond can be converted into polymers. They are far too useful
and therefore valuable to be burnt as fuels.