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Tectonic Plates

Earth's almost spherical has layers

Crust and upper part of mantle cut up into sections called tectonic plates

Like rafts- float on the mantle

Plates don't stay in one place

Earth's look changed over years

Plates move at few cm's each year

When tectonic plates under sea move away from each other, exposed mantle rises up and forms new crust

When crust forms, magnetised by Earth's magnetic field

Every few millions of year earth magnetic field swaps

So rocks polarity either normal or reversed

Can use this to tell age of different parts of Earth's crust

Geologists look at different features of rocks to tell what environment made in

Fossils- remains, imprints of dead organisms can tell you age of rock and conditions it was formed in

Underwater rocks contain shells and ripples created by sea and river

Can tell if rock was made underwater or in air by it's grains

Underwater- water borne grains

Air- airblown grains

Minerals in Earth's Crust

Different types of rocks contain different minerals

Minerals formed by lots of different processes

E.g: Sedimentation, evaporation, erosion, dissolving, mountain building

Chemical industries tend to set up near the resources

Limestone sedimentary rocks

Grey/ white and mainly made from calcium carbonate

Sedimentary rocks formed layers of sediment in lakes seas

Sediment come from bones or shells of plants or erosion from pre-existing rocks

Erosion weathering of rocks making sediment in sea bed and weight squeezes out water and fluids flowing through pores creates minerals binding rock together

Coal sedimentary rock

Made from mainly carbon

Salt left behind in evaporation of ancient seas and lots of underground rock salt especially in Cheshire and Teeside

Salt

Rock salt mix of salt and impurities

2 ways of extracting- mining or solution mining

Mining- Rock drilled, blasted, dug out brought to surface using machines

Salt obtained this way generally used on roads

Can be separated out and used as cooking salt and chemical salt

Solution Mining- Water injected into salt deposit

Dissolves into salt and makes brine

Pressure forces brine up stored into containers

Then refined and boiled to leave salt behind

Mining bad for environment

Leaves big holes where land can fall in on itself- called subsidence

Subsidence reduced by leaving caverns

Also mining requires lots of energy, usually comes from burning fossil fuels also causes pollution

In some hot countries shallow pools built filled with seawater and left to evaporate

Repeated several times then collected

Purest kind of salt- can be 100% sodium chloride

Salt in Food Industry

Salt used to enhance food flavour

Also used as preservative, keeps bacteria waya by drying out the meat and any bacterial cells

Some health issues with salt

Increase blood pressure

Been linked with stomach cancer

Hard to keep track of your daily salt intake

Gov has health guidelines on salt

Watch dogs made companies write percentage of GDA of salt that product has

Making people more aware of salt intake

Manufactures don't want to decrease salt because it could change flavour meaning company needs to make new recipe

Also product might not taste as good or last as long

Electrolysis of Salt Solution

Salt important for chemical industry

They put an electric current through the brine

Splits solution into hydrogen, chlorine and sodium hydroxide

Lots of useful products can be made from electrolysis

Chlorine: used in swimming pools and our water supply kills bacteria

Hydrogen: Used to make ammonia, changes oils into fat also used as fuel in fuel cells

Sodium hydroxide: used to make soap, oven cleaner paper pulp etc.

Large scale electrolysis can cause environmental problems

Uses fossil fuel

Mercury also released which is toxic

Asbestos also used- toxic can cause lung cancer

Chlorination

In UK chlorine added to water to kill bacteria even after water has been treated like in pipes

Not everyone has access to clean water

About a billion don't

Some people have to walk miles just to get dirty water

Countries with higher life expectancies have ability to supply clean water

Clean water reduces risk of cholera, diarrhoea and many more diseases

Chlorine needs to be made from sodium chloride or hydrogen chloride

Must be separated, can't just put salt in because properties are different

Can be separated either by electrolysis or oxidation of hydrogen chloride

Disadvantages of drinking chlorinated water:

H2O contains variety of organic compounds and chlorine reacts with them to make chlorinated hydrocarbons which are carcinogenic

Chlorine gas dangerous irritates respiratory systems can be dangerous during chlorination process

Alkalis

Alkalis react with acids to make salt and water

Neutralisation reaction

Carbonate means CO2 will be made too

Alkalis been used for 100's years

Used to turn oils+fats into soap

Used to neutralise acidic soil

They used to make alkalis from stale urine and burnt wood

Then more was needed so the started manufacturing it

First manufacturing used limestone and salt

Made LOTS of pollution and physical waste

Slowly released hydrogen sulfide which is toxic

Impacts of Chemical Production

Lots of chemicals used in industry to make: drugs, agricultural chemicals, plastics, metals etc.

Some chemicals stay in environment for very long time

Stay long if not broken down

Can end up being carried around and contaminating lot of different animals

Like DDT almost caused otters to disappear in south of England

Plasticisers can harm environment

PVC very popular polymer- used lots

PCB's can leach out which are toxic

Life Cycle Assessments

When product being made, manufactures need to think of products life cycle and reduce amount of pollution product causes as much as possible

Choice of materials:

Most products use water

Metals used quite widely, need to be mined and extracted from ore- takes up lots of energy

Crude oil used a lot as well, but needs to be obtained from ground and refined before used for raw materials- also takes up lots of energy

Manufacture:

Manufacturing takes up lots of energy and creates lots of pollution

When manufacturing need to think about how they are going to dispose of waste products

Some reuse waste products- reducing amount wasted

Using the product:

Using product can also damage environment

Paint can be toxic

Fertilisers can leach and contaminate rivers/ seas

Burning fuels releases greenhouse gases can lead to global warming

Product disposal:

Landfills take up lots of space and pollutes land and water

Some products incinerated- creates air pollution

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