Chemistry in Society – Summary File
Given below are some of the basics of what you will need to know for
this topic. In order to make sure that you have revised all aspects of
the unit, you also will have to look at your noted booklet.
Metals and Alloys
 Metals are a type of element, clearly marked in the periodic
table.
 The alkali metals (group 1) and the transition metals are metals
that all have similar chemical properties.
 Metals are hard, shiny, conductors of heat and electricity,
ductile (able to be drawn into wires) and malleable (able to be
beaten into shape). All metals are solid, bar mercury which is a
liquid at room temperature.
 Metal all conduct electricity due to having delocalised
electrons.
 Alloys are mixtures of metals with improved properties, e.g.
solder has a lower meting point than lead and tin which make it
up.
 Metals are finite and will run out thus the price of them is
increasing and we are trying to find better ways of recycling
them.
Reactivity Series:
 Metals can all be placed in a reactivity series, with the most
reactive metals at the top.
 Metals react with oxygen, water and dilute acid.
Differences in the reaction rates give an indication of the
reactivity of the metal.
 Metal + oxygen -> Metal Oxide
 Metal + Water -> Metal hydroxide + hydrogen
 Metal + Acid -> a Salt + hydrogen
 Ores are naturally occurring compounds of metals.
 The less reactive metals, including gold, silver and copper, are
found uncombined in the Earth’s crust and the more reactive
metals have to be extracted from their ores.
 Some metals can be obtained from metal oxides by heat alone;
some metal oxides need to be heated with other substances,
e.g. carbon or carbon monoxide; other metals cannot be
obtained by these methods.
 Iron is produced from iron ore in the Blast Furnace. The
production of carbon monoxide and the reduction of iron oxide
are the two key reactions which take place in the Blast
Furnace.
 The more reactive metals, including aluminium, are obtained by
electrolysis.
Electrochemical Cells:
 Electricity can be produced by connecting different metals
together, with an electrolyte, to form a simple cell.
 The cathode and the anode must be different metals to
produce a voltage. The electrolyte must be an ionic solution in
order for the ions to be free to move.
 The voltage between different pairs of metals varies and this
leads
to
the
electrochemical
series.
The
greater
the
difference
 Displacement reactions occur when a metal is added to a
solution containing ions of a metal lower in the electrochemical
series.
 The reaction of metals with acids can establish the position of
hydrogen in the electrochemical series.
 Electricity can be produced in a cell by connecting two
different metals in solutions of their metal ions.
 Electricity can be produced in a cell when at least one of the
half-cells does not involve metal atoms.
 Electrons flow in the external circuit (through the wire) from
the species higher in the electrochemical series to the one
lower in the electrochemical series.
 The purpose of the ‘ion bridge’ (salt bridge) is to allow the
movement of ions to complete the circuit.
Using Electricity:
 Electrolysis is the splitting up of an ionic compound using
electricity.
 Electricity can be used to electroplate, purify or protect
metals.
 Anodising is the protection of aluminium using an aluminium
oxide coating.
Corrosion:
 Corrosion is a chemical reaction which involves the surface of a
metal changing from an element to a compound.
 Different metals corrode at different rates.
 The term rusting is applied to the corrosion of iron.
 Both water and oxygen, from the air, are required for rusting.
When iron rusts, initially the iron atom loses two electrons to
form iron (II) ions which can be oxidised further to give iron
(III) ions.
Electrons lost by the iron during rusting are
accepted by the water and oxygen to form hydroxide ions.
 Ferroxyl indicator can be used to detect the presence of
iron(II) ions and hydroxide ions and turns blue in the presence
of Fe2+ ions.
 Acid rain increases the rate of corrosion and acid acts as an
electrolyte.
 Salt spread on roads increases the rate of corrosion on car
bodywork as salt acts as an electrolyte.
 When attached to metals higher in the electrochemical series,
electrons flow to the iron, and when attached to metals lower
down in the series, electrons flow from the iron.
 Iron does not rust when attached to the negative terminal of a
battery. This is called cathodic protection
 Electrons flowing to the iron prevents rusting.
 Anti-corrosion methods are used in everyday situations.
Painting, greasing, electroplating, galvanising, tin-plating and
coating with plastic give a surface barrier to air and water
which can provide physical protection against corrosion.
 Galvanising (covering iron in zinc) and the use of scrap
magnesium result in electrons flowing to the iron giving
sacrificial protection.
 Scratching tinplate increases the rate of rusting of iron.
Metals
 Metallic bonding joins metals together as positive nuclei are
surrounded by a sea of delocalised electrons (which allows
conduction).
 Oxidation is a loss of electrons by a reactant in any reaction. A
metal element reacting to form a compound is an example of
oxidation.
 Reduction is a gain of electrons by a reactant in any reaction. A
compound reacting to form a metal is an example of reduction.
 In a redox reaction, reduction and oxidation go on together.
 Ion-electron equations can be written for oxidation and
reduction reactions (see data book).
 During electrolysis, oxidation occurs at the positive electrode
and reduction occurs at the negative electrode.
 Fuel cells produce electricity using reactions of hydrogen and
oxygen.
 Materials and Plastics
 Synthetic materials are made by the chemical industry.
 Most plastics and synthetic fibres are made from
chemicals derived from oil.
 Examples of plastics include polythene, polystyrene,
perspex, PVC, nylon, bakelite, formica and silicones.
 Kevlar, which is very strong, and poly(ethenol), which
readily dissolves in water, are recently developed
plastics.
 The everyday uses of plastics are related to their
properties.
 Examples of synthetic fibres include polyesters, e.g.
Terylene, and nylon.
 For some uses, synthetic materials have advantages over
natural materials and vice versa.
 Biopol is a recently developed degradable plastic.
 Most plastics are not biodegradable (i.e. do not break
down naturally) and their low density and durability can
cause environmental problems.
 Some plastics burn or smoulder to give off toxic fumes,
including carbon monoxide.
 The toxic gases given off during burning or smouldering
can be related to the elements present in the plastic
(PVC=HCl and polyurethane = hydrogen cyanide HCN).
 Plastics can be either thermoplastic or thermosetting. A
thermoplastic is one which can be reshaped on heating. A
thermosetting plastic cannot be reshaped by heating.
 Monomers are small molecules, polymers are large and
monomers join up to form polymers in a polymerisation
reaction.
 Addition polymerisation
Plastics are made up of long chain molecules called
polymers .Polymer molecules are made from many small
molecules called monomers. Addition polymers are made
from small unsaturated molecules produced by cracking
by a process called addition polymerisation. The small
unsaturated molecules join together by the opening of
the carbon to carbon double bond. The name of the
addition polymer is related to the name of the monomer.
The repeating unit or the structure of an addition
polymer can be drawn given the monomer structure and
vice versa.
 Condensation polymerisation
Condensation polymers are made from monomers with two
functional groups per molecule. The repeating unit or the
structure of a condensation polymer can be drawn given
the monomer structures and vice versa. Polyesters are
examples of condensation polymers. An amine can be
identified from the functional group. Polyamides are
examples of condensation polymers.
Fertilisers:
 Fertilisers contain the elements N, P and K as these are
the essential elements needed by plants for growth.
 The Haber process takes nitrogen from the air and
hydrogen from natural gas to make ammonia (alkaline gas,
NH3). An iron catalyst is used as is high pressure and
moderately high temperatures.
 The Ostwald Process takes ammonia and oxygen to make
nitric acid. This is used to make fertilisers. This is an
exothermic reaction and uses a platinum catalyst.
 You should be able to do percentage by mass calculations.
Nuclear Chemistry:
 The atom has the following structure:
 Protons and neutrons have mass 1 and electrons have
almost no mass.
 Isotopes have the same atomic number but different
mass numbers, i.e. they have different numbers of
neutrons.
 There are 3 main types of radioactivity, that can be used
for a number of uses, including medicine and energy
generation:
 Half-life is the time it takes for radiation to decrease by
half.
You should expect to be able to do half-life
calculations.
Chemical Analysis:
 The concentration of acids/alkalis can be calculated from
the results of volumetric titrations.
 You should be able to do a variety of problem solving and
calculations on this topic.
This is a summary of what is in this topic – please look at your
notes for further information.