C3 CHEMICALS IN OUR LIVES

Question 1

What are the jobs of geologists?

Answer 1

they study rocks to see how the earths surface has changed. they look at how the rocks firm, how they change and when the changes happened.

Question 2

How was limestone formed

Answer 2

Britain was covered by sea:

• shellfish died forming sediments on the sea bed
• sediments compacted and hardened to form limestone, a sedimentary rock
• tectonic plate movements pushed the rock to the surface
• gradually rocks above were eroded away until limestone was exposed

Question 3

how was coal formed in Britain

Answer 3

Coal formed in wet swampy conditions when plants like trees and ferns died and became buried. this excluded oxygen, slowing down decay

Question 4

how was salt formed in Britain?

Answer 4

while Cheshire was covered by a shallow sea:

• rivers brought dissolved salts into the sea
• climate warming evaporated the water, leaving salt that mixed with sand blown by the wind
• rock salt formed and was buried by other sediments

Question 5

how did geologist find evidence for limestone formation?

Answer 5

limestone contains bits of shell fragments from sea creatures

Question 6

how did geologist find evidence for coal formation?

Answer 6

coal contains fossils of the plants that formed it

Question 7

how did geologist find evidence for salt formation?

Answer 7

Rock salt contains different shaped water eroded grains and wind eroded grains

Question 8

what are the uses for salt?

Answer 8

• the food industry
• source of chemicals
• to treat icy roads in winter

Question 9

how can we obtain salt?

Answer 9

evaporating sea water and mining underground deposits of rock salt

Question 10

Why is rock salt spread on icy roads?

Answer 10

• the rock is insoluble but the sand in the rock salt gives grip
• shows when roads have been gritted
• the salt in solution lowers the freezing point, prevent ice forming as easily

Question 11

Why is salt added in food?

Answer 11

for flavouring and as a preservative - a higher salt level bl prevents bacteria growths - too much salt is bad for you

Question 12

why are people worried about salt intake?

Answer 12

can cause high blood pressure, heart failure, kidney failure and strokes

Question 13

What is the department of health?

Answer 13

the are responsible for carrying out risk assessment for chemicals in food and telling the public about how food affects health

Question 14

What is neutralisation?

Answer 14

alkalis neutralise acids to make salts.

Question 15

What is the word equation for neutralisation?

Answer 15

acid + alkali > salt + water

Question 16

what are alkalis used for?

Answer 16

dying cloth, neutralising acid soul, making soap, making glass

Question 17

what were past sources of alkalis

Answer 17

stale urine and ash from burnt wood

Question 18

What was the first alkali to be manufactured and how was it done?

Answer 18

lime (calcium oxide) - done by heating limestone in line kiln using coal as fuel

Question 19

What is lime used for?

Answer 19

neutralising acidic solutions, making glass when heated with sand and removing impurities when iron is made

Question 20

What were used before modern dyes?

Answer 20

dyes from animals and plans

Question 21

What is Alum?

Answer 21

it’s a mordant that sticks dye to a fabric. it was purified by reacting it with ammonia contained in stale urine

Question 22

How does the Leblanc process make sodium carbonate

Answer 22

by reacting salt and limestone, heated with coal

Question 23

What are the waste products of the Leblanc process?

Answer 23

• large amount of an acidic harmful gas called hydrogen chloride
• produced heaps of solids waste called galligu , that slowly released hydrogen chlorine into useful substances

Question 24

harmful hydrogen chloride from the Leblanc process changed into useful substances. name useful substances

Answer 24

• chlorine used to bleach textiles prior to dying

- hydrochloric acid which is a starting material for making other chemicals

Question 25

how can chlorine be made?

Answer 25

reacting hydrochloric acid with manganese dioxide

Question 26

What is the pH and colour of an alkali?

Answer 26

greater than pH7 and it turns the indicator blue or violet

Question 27

why do we put chlorine in water?

Answer 27

To kill water borne microorganisms that cause diseases like cholera and typhoid

Question 28

What can electrolysis do?

Answer 28

break up compounds using an electric current

Question 29

what does the electrolysis of brine make?

Answer 29

chlorine gas, hydrogen gas, sodium hydroxide solution - have solutions and no waste

Question 30

what is the anode and cathode?

Answer 30

anode - positive electrode

cathode - negative electrode

Question 31

during brine electrolysis, what forms at the anode and cathode?

Answer 31

chlorine forms at the anode and hydrogen at the cathode

Question 32

what are the inductive uses of the products made in the electrolysis of brine

Answer 32

chlorine: for making plastics like PVC, in medicines and crop protection
hydrogen: for making margarine in as rocket fuel, in cells in vehicles
sodium hydroxide: for paper recycling, industrial cleaners and refining aluminium

Question 33

what are the environmental impact of brine electrolysis?

Answer 33

• chlorine products - eg fridges and aerosols are linked to ozone depletion
• chlorine increases risk of cancer
• the Mercury diaphragm method of electrolysis - Mercury waste
• plastics from chlorine - non-biodegradable

Question 34

How do we decide the level of risk of a particular chemical we need to know?

Answer 34

• how much of it is needed to cause harm
• how much it will be used
• the chance of it escaping into the environment
• who or what it may affect

Question 35

What does pvc contain?

Answer 35

it’s a plastic containing carbon, hydrogen and chlorine

Question 36

what is plasticised PVC used for?

Answer 36

to cover electrical wires, for clothing and for seat covers

Question 37

What is added to PVC to make it softer

Answer 37

small molecules called plasticisers

Question 38

What are PVCs risk on the environment?

Answer 38

it has long term effects on and fish and large amounts have been shown to harm animals

Question 39

what happens when PVC is burnt?

Answer 39

gives off toxic gases including dioxins. if eaten, these chemicals build up fat and are thought to cause cancer

Question 40

Why is it that many people dispute risk of PVC?

Answer 40

plasticisers are relatively new so long term studies are not possible

Question 41

what is the life cycle assessment (LCA)

Answer 41

it measures the energy used to make, use and dispose of a substance and its environmental impact

Question 42

at each stage of LCA, what do we need to consider?

Answer 42

• how much natural resources are required
• how much energy is needed or produced
• how much water and air is used
• how is the environment effected?