C3 Chemicals in our lives: Risks and Benefits (1)
B: Mineral wealth in Britain
A: A journey through geological time
The Earth’s outer layers are divided into a number of _______________
plates. Each plate contains ________ oceanic crust, often carrying some
___________ continental crust on top of it. The plates move because of
very slow ______________ currents in the underlying solid mantle. Most
major volcanic eruptions and _____________ happen at plate
boundaries. This movement means that Britain has experienced various
climates during its history and __________ for this is found in the
different rocks that make up the country.
Word bank: convection, dense, evidence, tectonic, earthquakes, lighter
In the 1950s a group of scientists showed that it was possible
to track the position of a slowly drifting country by studying
(magnetic/atomic) particles in the rock. Some sediments from
volcanic lava contain the mineral (magnetstone/magnetite).
This mineral gets its name from the magnetic properties of its
(crystals/fossils). Magnetite in lava can be magnetised in a
fixed direction once the rock has (cooled/warmed) enough.
The magnetism lines up in the direction of the Earth’s
magnetic field at the time the rock was formed. By measuring
the angle at which crystals are magnetised in rocks, scientists
work out the (longitude/latitude) at which the rock was
originally formed.
C: Salt: sources and uses
Salt can be used to preserve food and to add flavour to it. It can also be used to treat icy roads in winter
and as a source of chemicals such as chlorine. ______ _______ is extracted from the sea by evaporating
the water (e.g. east coast of Essex), ______ ________ is obtained by mining it from underground salt
mines (e.g. in North Yorkshire and Cheshire). Salt used for the chemical industry in Britain is obtained by
____________ _____________ .
Impurities like clay do not dissolve
and so stay underground.
The salt dissolves and is carried to the
surface in solution. It is called brine.
The crystals are separated from any
remaining brine by filtering or using
a centrifuge.
Salt crystals are recovered from brine
by evaporating the water.
Water is pumped into the rock.
Large scale pumping to extract brine in Cheshire in the 1870s eventually created large underground
holes. This led to widespread subsidence resulting in buildings collapsing. Nowadays, holes in the rock
are separated by pillars of rock to help prevent subsidence.
(label the Peak
District and
310 MYA
220 MYA
280 MYA
350 MYA
Sea water formed
shallow salt marshes.
Rock formed as the
water evaporated.
Peak district
Formed as dead
swamp plants
formed peat and
were compressed.
Sand and small
pebbles were
deposited in layers,
which were
Peak district
Formed as dead
animals and plants
sank to the bottom
of the sea and
formed fossils.
Peak district
D: Salt in food
Sodium from salt is an essential part of the diet. In your body it is found in
__________ , ________ and _________ . The main sources of salt in the
diet are __________ , ____________ and some dairy products such as
cheese. Health experts think that people eat too much salt. They think
that eating too much salt can raise people’s ___________ pressure and
can therefore increase the risk of ____________ ____________ .
Shabana: The research
does not support a
general recommendation
to reduce sodium intake.
Angie: There is
conclusive evidence
that moderate sodium
reduction lowers
blood pressure.
Joseph: Cutting salt in the diet
may be worthwhile for older
people with high blood pressure.
For people whose blood pressure
is normal, the evidence is not
strong enough to justify a
general reduction in salt levels.
Some people challenge the theory that reducing salt intake brings health benefits to all. Who is stating a
health benefit of reducing salt intake? ______________ Who suggests the group of people who might
benefit from reducing their levels? ______________
C3 Chemicals in our lives: Risks and Benefits (2)
E: Alkalis and their uses
Traditional alkalis were needed to _______________________________
One of the first pure chemicals made in Britain was alum. This was
used for dyeing cloth. Alum was made on the North East coast of
Britain, where rocks in the cliffs were rich in aluminium compounds.
F: Chemicals from salt – the foul way
(Label Runcorn by
the river Mersey)
(label the North
East coast of
Rock was roasted in
fires for many months
The solution was boiled to
evaporate most of the water.
Alkali was added to
neutralise the acids.
The solution was allowed to
cool in wooden casks and
alum crystals formed.
The resulting soluble
chemicals were put into
lead pans.
Rock was put into pits of
water and allowed to
Alkalis and their reactions – alkalis can neutralise acids
Alkaline hydroxide + acid
salt + water
Alkaline carbonate + acid
salt + carbon dioxide + water
What products are formed during these reactions?
1. Calcium hydroxide + hydrochloric acid
2. Potassium hydroxide + sulfuric acid
3. Sodium carbonate + nitric acid
G: Benefits and risks of water treatment
Water that is contaminated by __________ can sometimes carry fatal diseases such as ________ ,
typhoid, dysentery and gastroenteritis. Waterborne infections cause 1.7 million deaths per year. Those
who die are mainly __________ in developing countries. Chlorination of drinking water in Britain
became common in the early twentieth century.
Chlorination is used to __________________________
Using the graph, describe what happened to the
numbers of deaths from typhoid fever in the USA
following water chlorination.
____________________________________________ .
Another advantage of treating water with chlorine is __
____________________________________________ .
Why are some scientists concerned about chlorination? ______________________________________
How are trihalomethanes (THMs) formed? _________________________________________________
What are the suspicions about THMs? _____________________________________________________
Is there any evidence for this? ___________________________________________________________
How can the levels of THMs be limited? ___________________________________________________
3. The chemical produced when hydrogen
chloride is oxidised (8)
4. The name of the gas given off during the
Leblanc process (8,8,)
5. Hydrogen chloride dissolved in water
produces hydrochloric acid. What happens to
wildlife in rivers polluted with this acid? (4)
6. Alkalis were used in which industry in France
in the 1700s? (5)
7. The laws passed by the Government to
reduce the pollution produced by the chemical
industry (6,4)
8. The inventor of the process used to make
the alkali sodium carbonate from limestone
and salt (7)
1.The gas that smells of rotten eggs (8,7)
2. Chlorine is used to do what to paper and textiles? (6)
H: Chemicals from salt – a better way
Brine is a mixture of sodium chloride (
) in water (
So there are just four elements in brine, which can be
rearranged to make chlorine (
) , sodium hydroxide (
and hydrogen (
) .The chemical changes happen when an
electric current flows through the solution. The process is called
______________________ . The equipment is designed with a
porous membrane to keep the two main products, chlorine and
sodium hydroxide, separate because they react with each other
when they mix.
Environmental impact of electrolysis
Manufacturing chemicals from salt by electrolysis needs a lot of energy. How is most of this energy
(electricity) produced?
The industry is moving towards producing the electricity from renewable sources such as?
Until recently the most common system for the electrolysis of brine used mercury as one of the
metals in contact with the solution. What is the problem with using mercury?
C3 Chemicals in our lives: Risks and Benefits (3)
I: Protecting health and the environment
Chemicals in plastics and
Amount of chemical in
human blood
Amount of chemical
needed to be harmful
< 1 part per billion
The likelihood of a
hazard causing harm
Can cause cancer
Something that is
likely to cause harm
(Registration, evaluation and
authorisation of chemicals) was
introduced in the EU in 2007 to
collect information about the
hazards of chemicals to assess
risks. The responsibility for
control and safety of chemicals
is with the companies who
make them or use the.
J: Stages in the life of PVC
PVC is a synthetic polymer that is strong, easy to mould and quite cheap. It is also hardwearing, durable and can be used to make a wide variety of products. The stages in the
life of PVC products include production, use, and disposal. Label the statements P, U or D.
Used as window frames
Pipes are used underground
to carry drinking water.
Man made
Large doses
A LCA involves collecting data about each stage of the life
of a product. An assessment of this kind can show, for
example, what materials should be used to make
different products. Label the statements below C (cradle)
U (use) or G (grave).
What is the problem with plasticisers?
Materials used to make the product.
Shabana: There is
evidence linking
plasticisers with health
problems such as cancer
and infertility.
Water and chemicals needed to maintain
the product.
Energy and water used in
processing and manufacturing.
Who above would support a ban on the use of plasticisers? __________________________ If there is
no conclusive evidence that DEHP can cause harm, why do they have this opinion? ______________
Alternatives to using DEHP in medical equipment are expensive and not always available but the risk
of not treating a patient is greater than the very small risk of from exposure to the plasticiser.
Used as gutters
L: From cradle to grave
Plastic will not rot because it is not _______________ . Oil and products from oil, like plastic, are very
valuable. They lose value as they are used and end up as waste. This is not ___________ because the
materials cannot be used again. ____________ and reusing materials slow down the rate at which we
use up natural resources that are not renewable.
What are the most common plasticisers for PVC? ____________________________________________
Emily: PVC has been used for
over 50 years and in that time ,
there has not been a single
known case of anyone being
harmed as a result of phthalates.
Small molecules of vinyl
chloride monomers are
joined to make PVC polymers
Recycling – waste ground into
pellets, which can be reheated and
moulded into new products
K: Benefits and risks of plasticisers
What are plasticisers?
PVC sent to factories to be
moulded under heat and
Energy recovery – polymer waste is
burnt in incinerators and the
energy used to produce electricity.
Tipped into holes in
the ground as landfill
POPS (persistent organic pollutants) and pollutants
There are some synthetic chemicals that everyone agrees are _________
even in very small amounts. These are chemicals that do not ________
_______ in the environment for a very long time. This means that they
can spread around the world in air and water, and can ______________
in the fatty tissue of animals, which people then eat.
Gurpal: The plasticiser DEHP has been
shown to affect the development of the
reproductive system and sperm in young
male animals. These effects have not
been found in human babies, but it has
not been possible to show that there is no
Combining chlorine
and ethene
Energy needed to dispose of the product.
Energy needed to use the product.
Raw materials obtained and
processed to make useful materials.
Space needed to dispose of it.
Energy needed to maintain the product.