C3 CHEMICALS IN OUR LIVES Flashcards
(42 cards)
What are the jobs of geologists?
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.
How was limestone formed
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
how was coal formed in Britain
Coal formed in wet swampy conditions when plants like trees and ferns died and became buried. this excluded oxygen, slowing down decay
how was salt formed in Britain?
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
how did geologist find evidence for limestone formation?
limestone contains bits of shell fragments from sea creatures
how did geologist find evidence for coal formation?
coal contains fossils of the plants that formed it
how did geologist find evidence for salt formation?
Rock salt contains different shaped water eroded grains and wind eroded grains
what are the uses for salt?
- the food industry
- source of chemicals
- to treat icy roads in winter
how can we obtain salt?
evaporating sea water and mining underground deposits of rock salt
Why is rock salt spread on icy roads?
- 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
Why is salt added in food?
for flavouring and as a preservative - a higher salt level bl prevents bacteria growths - too much salt is bad for you
why are people worried about salt intake?
can cause high blood pressure, heart failure, kidney failure and strokes
What is the department of health?
the are responsible for carrying out risk assessment for chemicals in food and telling the public about how food affects health
What is neutralisation?
alkalis neutralise acids to make salts.
What is the word equation for neutralisation?
acid + alkali > salt + water
what are alkalis used for?
dying cloth, neutralising acid soul, making soap, making glass
what were past sources of alkalis
stale urine and ash from burnt wood
What was the first alkali to be manufactured and how was it done?
lime (calcium oxide) - done by heating limestone in line kiln using coal as fuel
What is lime used for?
neutralising acidic solutions, making glass when heated with sand and removing impurities when iron is made
What were used before modern dyes?
dyes from animals and plans
What is Alum?
it’s a mordant that sticks dye to a fabric. it was purified by reacting it with ammonia contained in stale urine
How does the Leblanc process make sodium carbonate
by reacting salt and limestone, heated with coal
What are the waste products of the Leblanc process?
- 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
harmful hydrogen chloride from the Leblanc process changed into useful substances. name useful substances
- chlorine used to bleach textiles prior to dying
- hydrochloric acid which is a starting material for making other chemicals
