OCR 21st Century C3

Chemicals in our Lives
1. Alkalis
  1. before industrialisation, alkalis were needed to neutralise acid soils, make chemicals that bind natural dyes to cloth, convert fats and oils into soap and to manufacture glass
    1. traditional sources of alkali included burnt wood or stale urine
    2. increased industrialisation led to a shortage of alkali in the nineteenth century
      1. The Leblanc Process- The first process for manufacturing alkali from salt (sodium chloride) and limestone (calcium carbonate) using coal as a fuel to produce sodium chloride
        It caused pollution by releasing large volumes of hydrogen chloride and creating great heaps of waste that slowly released a toxic and foul-smelling gas (hydrogen sulfide)
        oxidation can convert hydrogen chloride to chlorine.
  2. Acid + Alkali = Salt + Water
    1. Compound that forms OH- ions when dissolved in water
      1. soluble hydroxides and carbonates are alkalis
        Acid + hydroxide = Salt + Water
        Acid + carbonate = Salt + Water + CO2
2. Chlorine
  1. chlorine is used to kill microorganisms in domestic water supplies and as a bleach
    1. The chlorination of drinking water in the early 20th century led to a steep decline in deaths from typhoid.
      1. Advantages of Chlorination- some chlorine remains in water so it can protect against possible contamination in the pipes that carry it from the treatment works to the consumer. Chlorine also removes unpleasant smells, tastes and colours and helps stop microorganisms (algae) from growing in storage tanks
        Disadvantages of Chlorination- Water contains organic matter (fragments of leaves) which reacts with chlorin to form THMS or chlorinated hydrocarbons, many of which are carcinogenic.
        The increased risk of cancer is small compared the risks of untreated water. Cholera epidemic could kill thousands
        Chlorine gas is very harmful if it's breathed in- it irritates the respiratory system. Liquid chlorine can cause severe chemical burns
      2. WHO estimated in 1995 1billion people did not have clean water
        In developing countries, it is expensive to get clean water. In rural parts of Africa and India, people have to walk miles just to get any water
        The biggest increase of life expectancy is linked to supply of clean water
        In 2004 WHO stated that improving drinking water quality would reduce diarrhoeal diseases by up to 40%
3. Safe and Sustainable products
  1. there is a large number of industrial chemicals with many widespread uses, including consumer products, for which there is inadequate data to judge whether they are likely to present a risk to the environment and/or human health
    1. some toxic chemicals cause problems because they persist in the environment, can be carried over large distances, and may accumulate in food and human tissues
      1. bioaccumulation- build up of chemicals in organisms as the chemicals travel through the food chain e.g. pesticides
        the consumer at the top of the food chain is most affected as it has the highest concentration of harmful substances (from eating much contaminated animals)
    2. PVC is a polymer that contains chlorine as well as carbon and hydrogen
      1. plasticizers used to modify the properties of PVC can leach out from the plastic into the surroundings where they may have harmful effects
        A Life Cycle Assessment (LCA) involves consideration of the use of resources including water, the energy input or output, and the environmental impact, of each of these stages
        making the material from natural raw materials
        making the product from the material
        using the product
        disposing of the product
        Products dumped in the landfill. This takes up space and pollutes the land and water e.g. plastic and paint into water. Products may be incinerated which causes pollution
        Paint gives off toxic fumes. Burning fuels release greenhouse gases and other harmful substances. Fertilisers can cause bioaccumulation.
        Manufacturing uses lots of energy. Can cause harmful pollutants and gases e.g. CO or HCL. Are there any waste products? Correct disposal of the waste products. Can any waste products be recycled?
        Mined and extracted from ores requiring vast amounts of energy, thus causing pollution. crude oil is non-renewable and refining it requires lots of energy, which generates pollution
Rocks, Minerals & Plate Tectonics
1. Plate History
  1. movements of tectonic plates, due to convection currents in the mantle, mean that the parts of ancient continents that now make up Britain have moved over the surface of the Earth
    1. Magnetite- is a mineral found in many volcanic lavas and some sediments
      1. Geologists use it to track the very slow movement of the continents
      2. When lava cools into rock, the magnetite within it is magnetised in a fixed direction.
        The magnetisation lines up with the Earth's magnetic field at that time
        Near the equator, the magnetisation lies horizontally
        Nearer the poles, the magnetisation is at an angle to the horizontal
        By measuring this angle, geologists can work out the latitude at which the rock was formed
        the movements of continents means that different rocks in Britain formed in different climates
        geologists explain most of the past history of the surface of the Earth in terms of processes than can be observed today. E.g. you can find out about the history of a sedimentary rock i.e. sandstone by looking at the size and shape of the sand grains
2. Rock formation
  1. Erosion- the natural weathering of large pieces of rock by the rain and wind, which creates tiny particles of sediment that are washed away and end up at the bottom of a sea or lake
    1. Sedimentation- shells, bones and small pieces of rock fall to the seabed where they form a layer. Over millions of years, the layers of sediment get buried under more layers and the weight pressing down squeezes out the water
      1. Geologists look at different features of rock to learn about the environment in which they were formed
        Fossils- they are the remains or imprints of dead organisms. They tell you about the age of the rock and the conditions in which they were formed
        rocks formed underwater contains, shells, fish bones and ripples
        the sediment that forms the rocks will either have been carried by water or air. By looking at the shape of the grains found in sedimentary rocks, you can tell if the rock was formed underwater (it'll contain water-borne grains) or on the surface (it'll contain air-blown grains)
  2. Coal is formed by the fossilisation of layers of plant matter. Some hard coal is formed when coal deposits are put unde high pressure and temperature. This can happen during the process of mountain building
  3. Evaporation- When ancient seas containing salt evaporated salt was left behind. This was buried and compressed by other layers of sediment over millions of years
    1. There are massive deposits under Cheshire and Teeside.
    2. dissolving- minerals eroded from rock and salt dissolve into water
  4. Mountain forming- when mountains are formed, the Earth's crust is thrust upwards exposing new and buried sediments and minerals
3. chemical industries grow up where resources are available locally, e.g. salt, limestone and coal in north west England.
Salt- Sodium CHloride
1. Uses of salt
  1. Roads- Rock salt contains impurities, it is used to prevent ice forming as once dissolved, the salt lowers the freezing point of water to around -5oc
  2. Industry- During solution mining, a brine is formed. This brine can be electrolyzed by passing a current through it. This splits the brine into hydrogen, chlorine and sodium hydroxide
    1. Chlorine- Disinfectants, killing bacteria (water purification), household bleach, plastics (PVC), hydrochloric acid and insecticides
    2. Hydrogen- Used to make Ammonia (Haber Process), Used to change oils into fats for making margarine (hydrogenated vegetable oil) and used as a fuel in fuel cells, and for welding and metal cutting
    3. Sodium Hydroxide- Very strong alkali: soap, oven cleaner, ceramics, organic chemicals, paper pulp and household bleach (NaOH+Cl2).
  3. Flavouring/ Preservative- Because humans need sodium in their diet, they naturally seek out salty foods. People like the taste despite the health risks. In meats, salt absorbs the water from bacterial cells, thus killing the bacteria and preserving the meat
    1. Eating too much salt may cause high blood pressure for about 30% of the UK population. Increase the chance of heart attacks, stokes, stomach cancer, osteoporosis and renal failure
2. Obtaining salt
  1. Mining- Rock salt is drilled, blasted and dug out. This method produces rock which is 90% NaCl (mineral halite) and the rest is impurities, mainly clay
  2. Solution mining- Hot water is pumped under pressure down into the rock salt layers in an out pipe. The hot water dissolves the salt to form a concentrated brine solution, which under pressure, is pumped back to the surface up through the inner pipe.
    2. Brine can be stored until electrolyzed or evaporated to remove any impurities, thus making it safe for human consumption
  3. Mining requires energy produced by the burning of fossil fuels, creating pollutants
  4. Subsidence- Large underground caverns are produced, which can cause land above to collapse and flooding. The risk can be reduced by having well-supported caverns (pillars of rock) or spacing caverns apart and filled in
  5. In hot countries, sea water flows into shallow pools and it is left to evaporate. It can form 100% pure NaCl
3. Salt in the Diet
  2. Government departments such as the Department of Health and the Department for Environment, Food and Rural Affairs, have a role in
    1. carrying out risk assessments in relation to chemicals in food
    2. advising the public in relation to the effect of food on health.

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OCR 21st Century C3

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	Created by Pritesh Patel over 8 years ago