MATERIALS and their USES
- general index AND examples of uses of materials, relating their properties to
a particular application
Brown's Chemistry GCSE/IGCSE/O level Revision Notes
A GENERAL SURVEY OF
Properties of materials and
choosing a material for a particular use - this page
Part 1. General introduction to nanoscience,
and commonly used terms explained
Part 2. NANOCHEMISTRY - an introduction and potential
Uses of Nanoparticles of titanium(IV) oxide, fat and silver
From fullerenes & bucky balls to carbon nanotubes
Cubic and hexagonal boron nitride BN
Problems, issues and
implications associated with
Chromogenic materials - Thermochromic, Photochromic & Electrochromic Materials
Shape memory alloys e.g. Nitinol & Magnetic Shape Memory Alloys
Shape memory polymers, pH and temperature sensitive-responsive polymers,
performance polymers like kevlar
Gore-Tex, Thinsulate and Teflon-PTFE
Piezoelectric effect/materials & Photomechanical materials
Examples of how we use materials
Ceramics, polymers and composites are typical
categories of materials used in everyday life, transport and industry.
Most of the glass we use is relatively cheap
soda-lime glass, made by heating a mixture of sand, sodium carbonate and
limestone (limestone chemistry,
glass and ceramics). More expensive borosilicate glass, is made from sand and
boron trioxide, and melts at higher temperatures than soda-lime glass - good for
laboratory apparatus! Clay ceramics, including pottery and bricks, are made by
shaping wet clay and then heating to a high temperature in a furnace.
The properties of polymers depend on what
monomers they are made from and the conditions under which they are made. For
example, low density (LD) and high density (HD) poly(ethene) are produced from
ethene using different catalysts and reaction conditions (see
thermosoftening addition polymer notes). These are
thermosoftening polymers consisting of individual, tangled polymer chains and
melt relatively easily when they are heated. This contrasts with
thermosetting polymers consist of polymer chains with cross-links between them
and so they do not melt when they are heated (see
thermosetting polymer notes).
Most composites are made of two materials,
(i) a matrix or binder surrounding and binding together (ii) fibres or fragments
of the other material, which is called the reinforcement. Examples of composites
wood is a natural composite of cellulose
fibres strongly held together by a polymer matrix chemically derived from
cross-linked cellulose structures (similar in this respect to man-made
concrete mixture (aggregate of sand,
gravel and cement) - the sand and gravel act as reinforcement, used for
basement flooring and road surfaces, but the concrete can also be set with
reinforced with steel rods embedded in it, widely used as a construction
resin-fibreglass - the polymer monomer
mixture polymerises via a catalyst and sets hard to form a hard strongly
bonded material (thermosetting polymer) and the set resin reinforced by the
glass fibres embedded in it, this is a very strong low density composite
material, its used for car body work, boat hulls, sports equipment e.g.
some more technologically
advanced composites are made from carbon fibres or carbon nanotubes instead of
glass fibres, carbon fibre composites are based on a polymer matrix which are
reinforced by carbon fibres or carbon nanotubes, these composites are very
strong and of low density ('light'), they are quite costly to produce but
are widely used in the aerospace industry, sports car bodies,
It is important to be able to compare the
physical properties of glass and clay ceramics, polymers, composites and metals
and explain how the properties of materials are related to their uses and select
natural polymers, structure, function and
choosing a material for a particular use
Part 1. Natural and synthetic materials
Reminders: All materials are
atoms of various elements and they may be pure elements, pure compounds or
mixtures of elements and compounds.
For definitions and explanations
with examples see
ideas and definitions in Chemistry.
This section is more about ideas and decision making
than learning lots of facts.
Be able to explain why a material is best suited for
a particular purpose based on its characteristic properties.
Naturally occurring materials which have proved
Materials from plants e.g.
The timber from trees is used as a
construction material and pulped to make paper.
The cotton to make clothing fabrics
is grown in fields of the cotton plant.
Latex rubber is collected as a sticky
fluid from rubber trees
Wool for clothing comes from shearing
Leather goods are made from the skin
Silk, a fine weaving material is
obtained from silkworm larva.
To compliment, and in many cases supersede these
naturally occurring materials, we humans have developed an enormous range of ...
The main advantage of man-made synthetic
materials compared to natural materials is that you can design their
properties to suit a particular use and develop a better product by
chemically changing the structure of the material and how it is processed.
The extraction of metals from raw
materials from the Earth's crust - ores are mined and processed to produce iron, copper, titanium,
aluminium, which are converted into lots of different things and variety of
properties enhanced by making alloys to suit specific technical
Plastics - polymers with a huge range of
properties and uses have been developed from the products of crude oil in
the petrochemical industry e.g.
Synthetic fibres like nylon and polyester
can replace silk, cotton, wool and they can be made strong but
flexible/stretchy, waterproof ...
plastics don't rot like wood so can replace wooden
window frames, they don't corrode like metals to can replace iron/lead
piping and guttering,
synthetic rubber polymers replaces natural rubber
(though car tyres are still made of natural rubber and other materials),
insulating thinsulate can replace wool,
synthetic pigments mixed with solvents and
binding agents make hard wearing long lasting coatings, and have mainly replaced traditional paints made from mineral
powders + egg yoke + linseed oil.
Typical important physical properties of
Mainly physical characteristics
here, but chemical character is very important too and it is the properties of a
material that decide what it can be used for. So, knowledge of the properties of
materials helps you to decide on the suitability of a material for a particular
purpose i.e. what is best for the job! The effectiveness of a material is
how good it is for the function its supposed comply with.
For properties like strength,
stiffness and hardness, you would need to do a 'fair test' of pieces of
the same size material to get an accurate comparison e.g. a similar rectangular
The strength of a material is
measure of how much it can resist a force applied to it.
You might measure the force to
break a bar of the material, or what force is needed to permanently deform
it, that is changing its shape without snapping it.
There are two types of strength
values of importance, depending on how you apply the force to a material.
This is how much a material
can resist being pulled in tension until it breaks.
Ropes or chains on pulley
systems for lifting objects or steel cables supporting the road of a
suspension bridge, all need to have a high tensile strength or they
would snap under the weight of the load!
This is how much a material
can be compressed ('pushed') before it gives way or squashed and
materials like stone, bricks or concrete all have a high 'compression'
strength which is needed to support the weight of the rest of the
building they support.
Combination of tensile plus
Sometimes materials must be
strong in both tension and compression e.g. cross-beams in roofs which
get both pulled and compressed.
The stiffness of a material is a
measure of how easily it bends when a force is applied to it, but without
permanently deforming it i.e. the material springs back to its original
shape. A very stiff material hardly bends when a force is supplied.
Materials like stone, brick
and concrete are very inflexible, but blocks of most plastics and wood
are flexible and will all bend to some extent without breaking. Rubber
is one of the most flexible of materials and can be bent and stretched
by quite some margin and still spring back to its original shape.
Note that the thickness of
the material is important when considering 'stiffness'. Thin sheets of
almost any solid can be bent so far without breaking e.g. strands of
glass fibre, steel spring.
The hardness of a material is a
measure of difficult it is to cut into, so materials like diamond and
granite are very hard and butter and sodium metals are soft materials and
easily cut into.
Diamond is one of the
hardest substance is know and is used to put a strong cutting edge on
cutting tools and some industrial drills have diamond tipped tips.
Diamonds are so hard that they can only be cut by other diamonds!
The density of an object is a
measure of the mass of an object in a particular volume.
Density = mass / volume and is
usually measured in g/cm3 or kg / m3
The density of water is 1.00
g/cm3, the plastics poly(ethene) and poly(propene) are 0.92
to 0.98 g/cm3 (hence they float on water polluting the
surfaces of rivers, lakes and seas), nylon is 1.11 to 1.18 g/cm3, metals
have a wide range of density e.g. sodium floats on water, but most
metals sink in water (unless you shape them like a boat!).
For many contexts of
construction like aircraft wings and fuselage you would like a like a
low density ('lightweight') material hence the use of aluminium and
titanium alloys rather than steel.
Densities of some metals
in g/cm3: sodium 0.97, aluminium 2.70, titanium 4.54,
iron (~steel) 7.87, gold 19.30
States of matter density: solid
> liquid >>> gas. Solids and liquids have the highest densities because the
particles are close together. Gases have very low densities because the
molecules are so far apart as they fly around through mainly empty space!
Durability isn't something that
is easily quantified, but you should expect any product to have a reasonable
'working life'. Phrases like 'hard wearing', 'weather resistant' are a bit
vague, but they mean a lot to the consumer!
So, how long will the
material of a product last? or should last?
You don't want clothing
fabrics wearing away after a few months of wear, you expect the soles of
you shoes to last a reasonable length of time.
You don't want a carrier bag
to fall apart before your reach the car after leaving the supermarket!
You don't want the car tyres
wearing away after just a few thousand miles!
Very pure materials have quite
sharp melting points where the solid becomes a liquid e.g. water 0oC,
sodium chloride 801oC. However, many materials are a mixture of
different materials e.g. metal alloys or a range of different sized
molecules e.g. thermoplastics like poly(ethene), and in these cases the
material tends to melt over a wider temperature range. In the case of
polymers, they have a softening point and very gradually become a liquid
over the next few tens of degrees rise in temperature.
brief summary of widely used materials and their properties
(initial thoughts, still
which you should be able to relate to their
uses, and of course, where they are not used!
What a material can be used for is very
dependant on its properties, though cost can be a significant factor too.
||metals - alloys
||polymers - plastics
||glass, bricks and other ceramics
|Hardness - strength - rigidity -
||usually strong and fairly
rigid, but may need alloying with other metals to make them stronger,
||relatively soft and flexible
without breaking, though thermosetting polymers (thermosets) or rigid
PVC can be quite hard and brittle,
||very hard and rigid, not
flexible, but brittle and easily shatter when struck
|Heat related properties
||usually high melting point
||relative low softening -
melting points, thermosets may not melt but degrade at higher
||high melting point
||concrete has good thermal
|Thermal (heat conductivity)
||usually a good thermal
||good thermal insulator
||concrete is an insulator
||usually a good electrical
||good electrical insulator
||moderately (e.g. Al) to high
density (e.g. Fe)
||low density if based on
|Malleability, ductility, can it be
||malleable (easily pressed or
beaten into shape), ductile (easily drawn out into wire)
||some polymers can be drawn
out to form quite strong fibres, thermosoftening plastics are easily
moulded when warmed
||wet clay can be moulded
before firing in a furnace, but not afterwards!
||composites are malleable or
ductile, can't be moulded, but resins can be cast in moulds
|Durability to the environment
(e.g. water, atmosphere)
||may need protection from
corrosion which is relatively cheap low carbon steel, Aluminium has
natural protective oxide layer, non-porous,
||water repellent surface
||bricks are porous to water,
but glass is not porous and water-proof
||attractive shiny surface,
||properties depend on the
composition e.g. matrix, binder or reinforcement
||electrical wiring, cutlery,
strong sheeting e.g. aircraft, ships, car bodies
||clothing, insulators in
electrical or heat insulation, anything that might corrode which could
be replaced e.g. with plastic
||metals - alloys
||polymers - plastics
||glass, bricks and other ceramics
Case Study 1
Choosing the material for parts of a car
Case study 2
Well actually, lots on 'mini-cases' of
'suitability' to get you thinking as broadly as possible!
Rubber needs to be
strong, soft and flexible to be used for car tyres. Vulcanisation with
sulfur makes it tougher and hardwearing, so it lasts longer - an example of
modifying the properties of a material by extra processing.
Cooking utensils for the
kitchen need to be made of a strong, high melting, good heat conducting, not
toxic (aluminum is not used now!) material like stainless steel or iron.
Oven dishes are made of heat resistant (high melting) ceramic materials.
Children's toys must be
made of a tough durable material (stiff & strong), that is non-toxic,
hard-wearing (''play resistant'!) and of low density. Not surprisingly,
thermosoftening plastics like poly(ethene) and poly(propene) are mass
produced to fulfil our children's needs, and such plastics are easily
moulded into an infinitely range of objects, which are readily brightly
coloured with an array of pigments!
Clothing fabric needs to
be made of hard wearing fibres like nylon or terylene with a high tensile
strength, but it mustn't be stiff (must be very flexible) and in the case of
children's clothing or nightwear it must be fire resistant - so the material
must incorporate a flame retardant substance.
Many 'older' materials have
been replaced by more 'modern' synthetic materials e.g.
Strong plastics like
poly(propene) have replaced iron for drain-pipes and guttering. The
plastic doesn't break easily like brittle iron AND they don't rust and
corrode away in bad weather!
Some compact discs (CDs)
were originally made using a layer of aluminium to digitally record the
sound, but this was prone to slow corrosion, so after some time the
sound quality of reproduction deteriorated. CDs are now made from a very
tough, hard wearing and slightly flexible polycarbonate plastic that
will NOT corrode! (being plastic!) ...
... and while we are in the
music business, very old records were made of a very brittle material
that easily shattered and so few have survived, but modern 'vinyl
records' are made from strong and slightly flexible PVC plastic
[poly(chloroethene), old name polyvinyl chloride] which is far
less likely to break, even if dropped!
Plastics - polymers have
a wide variety of physical characteristics, they can be hard, strong, stiff
(rigid), flexible, low or high density, soften easily on heating or quite
heat resistant, some are easily moulded when softened on heating
(thermosoftening, the casing of many objects in the home), others set really
hard and are strong and don't melt (thermosets, worktops), strong fibres
like nylon for outdoor clothing and rope fibres.
USEFUL EXTRA READING ON MATERIALS and
This page can't cover all the
materials or contexts you may come across on your course or in the exam,
so, for more on the uses of
materials where their use is related to their properties see ...
poly(ethene), poly(propene), uses, problems, recycling
Condensation polymers, Nylon & Terylene,
comparing thermoplastics, fibres and thermosets
Metals - properties and uses
metals be made more useful? (alloys of Al, Fe, steel etc.)
The importance of titanium,
uses of alloys
Giant covalent structures and uses
Structure and properties of metals
Uses of carbon nanotubes
and checkout the 'smart
materials' index on this page Parts 2 to 6 and 8.
KS4 Science relating properties to
uses of natural synthetic materials GCSE chemistry guide notes on relating
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synthetic materials USA US grade 8 grade 9 grade10 relating properties to uses
of natural synthetic materials chemistry comparing the properties and uses of
metals, polymers, composites, glass and ceramics