C3 Flashcards
(33 cards)
how do geologists explain most of the past history of the surface of the Earth?
geologists explain most of the past history of the surface of the Earth in terms of processes than can be observed today
what has made up Britain (in terms of tectonic plates)?
Movements of tectonic plates mean that the parts of ancient continents that
now make up Britain have moved over the surface of the Earth. The movements of continents means that different rocks in Britain formed in different climates
how do geologists track the movement of continents over the surface of the Earth?
geologists use magnetic clues in rocks to track the very slow movement of
the continents over the surface of the Earth
what processes have led to the formation of valuable resources found in England?
processes such as mountain building, erosion, sedimentation, dissolving and
evaporation have led to the formation of valuable resources found in England including coal,
limestone and salt
what do geologists study to find evidence of the conditions under which sedimentary rocks were formed
geologists study sedimentary rocks to find evidence of the conditions under which they were formed, including:
- fossils
- shapes of water borne grains compared to air blown grains
- presence of shell fragments
- ripples from sea or river bottom
where do chemical industries form?
chemical industries grow up where resources are available locally, e.g. salt,
limestone and coal in north west England.
what is salt used in (industry wise)?
- salt is used as a source of chemicals
- to treat icy roads in winter
how can salt be obtained?
salt can be obtained from the sea or from underground salt deposits. underground salt can be obtained by mining, or by solution mining
why is rock salt spread on icy roads?
- the rock is insoluble but the sand in the rock salt gives grip
- it shows up so people know when roads have been gritted
- the salt in the solution lowers the freezing point, preventing ice from forming easily
why is the method used to obtain salt dependant on how the salt is to be used?
- mining does not leave pure salt
- solution mining is when salt crystallises and is separated from any remaining brine by filtering
what is solution mining?
water is pumped at high pressure into the rock salt, the salt dissolves and the salt solution is pushed to the surface. this method is more efficient
how can the methods of obtaining salt have an impact on the environment?
Extracting salt in solution can create large underground caverns. This can lead to bedrock collapsing and as a consequence, cause the lowering of the Earth’s surface. This is known as subsidence. It can be avoided by sensibly spacing out the holes created so the surface is supported by a sufficient amount of rock underground.
Why is salt important to the food industry?
- it is used as a preservative because a higher level of salt prevents bacteria growth
- it adds taste
what are the health implications of eating too much salt?
too much salt can cause
- high blood pressure
- heart failure
- strokes
what do government departments have a role in doing (salt wise)?
Government departments, such as the Department of Health and the Department for Environment, Food and Rural Affairs, have roles in:
- carrying out risk assessments in relation to chemicals in food
- advising the public in relation to the effect of food on health.
even before industrialisation, what were alkalis needed for?
even before industrialisation, alkalis were needed to: -neutralise acid soils
- make chemicals that bind natural dyes to cloth
- convert fats and oils into soap
- to manufacture glass
what were the traditional sources of alkali?
traditional sources of alkali included burnt wood or stale urine
what happens when alkalis neutralise acids?
alkalis neutralise acids to make salts
name some alkalis
- soluble hydroxides
- carbonates
what are the products of the reactions of hydroxides and carbonates with acids
hydroxide + acid → salt + water
carbonate + acid → salt + water + carbon dioxide gas
what did increased industrialisation lead to?
increased industrialisation led to a shortage of alkali in the nineteenth century
what did the first process for manufacturing alkali from salt and limestone cause?
The first process for manufacturing alkali from salt and limestone using coal
as a fuel caused pollution by releasing large volumes of an acid gas (hydrogen chloride) and
creating great heaps of waste that slowly released a toxic and foul smelling gas (hydrogen
sulfide). pollution problems can sometimes be solved by turning wastes into useful
chemicals
what can oxidation convert hydrogen chloride to?
oxidation can convert hydrogen chloride to chlorine, and that the properties of
a compound are completely different from the elements from which it is made
what is chlorine used for?
chlorine is used to kill microorganisms in domestic water supplies and as a bleach
