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C2a Structure of Earth, Plate tectonics and Igneou

The Earth has a layered structure. The thin rocky crust floats on the mantle and at the centre is the hot iron core.Radius is 6370KM

Crust and outer mantle are called the Lithosphere. This is rigid and cold and is divided into tectonic plates that are less dense than the mantle so float upon it.. Convection currents in the mantle cause the plates to move. (2.5 com per year) Earthquakes and volcanic eruptions occur at plate bounderies.

Subduction + process of one tectonic plate being pushed under another as they move.

Oceanic plates are denser than continental plates. At oceanic margins the oceanic plates cool , they collide with continental plate and get pulled under - subduction-  Subducted oceanic plate melts and volcanoes can occur.

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C2a Structure of Earth, Plate tectonics and Igneou

Alfred Wegener - Continental drift 1914- only proved in 1960's

Magma = molten rock under E's surface

Lava is liquid rock that cools to form igneous rocks containing a variety of crystal sizes. Size of crystal depends on rate of cooling. Slow = large.

Basalt= rich in iron forms from runny lava.

Gabbro = rich in iron but larger crystals cooled more slowly

Rhyolite = Rich in silica forms form thick lava  produces lava bombs and volcanis ash.

Granite= rich in silica but larger crystals cooled more slowly

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C2 b Construction Materials

Limestone ( calcium carbonate) is a  sedimentary rock used as a building material

Sedimentary rock = formed fom sea creatures on the floor of the oceans built up to a thick layer.

metamorphic rock = Rock formed as Sedimentary rock but changed by effects of high pressure and temperature.

Igneous rocks (granite) and metamorphic roxks (marble) are harder than sedimentary rocks.

Marble= (calcium carbonate)m metamorphic rock harder than limestone.  small grains held tightly together.

Granite = Igneous rock harder than marble = Crystals are joined together more strongly.

Thermal decomposition= process breaking compound down  into simpler compound by heat.

Limestone is heated with clay to form cement. Cement water and sand form concrete which can be reinforced with steel = composite material.

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C2 c Copper

Copper metal is extracted from copper ore by heating it with carbon.This is called reduction because oxygen is removed.

Copper = good conductor of heat and electricity, ductile easily made into wires, unreactive with other metals good for water pipes.

Electrolysis = Process which melted or dissolved ionic compounds are broken down by passing an electric current through them.

Copper can be extracted from its ore by heating it with carbon. Impure copper is purified by electrolysis in which the anode is impure copper, the cathode is pure copper, and the electrolyte is copper sulphate solution.During the process of electrolysis the positive copper ions move towards the negative electrode and form pure copper metal.

Electrolyte= Liquid that will conduct an electric current and decompose.

Electrode = Conductor through which an electric current enters or leaves a melted or dissolved ionic compound in electrolysis

Cathode = pure copper Negatively charged electrode   Anode= impure copper positively charged electrode

Recycling copper saves resources, energy and reduces waste.

 

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C2 c Alloys

An alloy is a mixture of two elements, one of which is a metal. Alloys often have properties that are different to the metals they contain. This makes them more useful than the pure metals alone. Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.

alloy              main metal(s) in alloy typical use

amalgam       mercury              dental fillings

brass            copper and zinc       hinges, electrical plugs

solder l          lead and tin          joining metals

Smart alloys have unusual properties. Nitinol is an alloy of nickel and titanium, and is known as a shape memory alloy. If nitinol is bent out of shape, it returns to its original shape when it is either heated or an electric current is passed through it.  makes it useful for making spectacle frames - they return to their original shape if they are put in hot water after bending them.

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C2 d Corrosion and cars

Rusting is metal corrosion -occurs iron in contact with air and water

Corrosion- reaction of metal with chemicals, esoecially water and oxygen in the air. Weakens structures made of metal

Oxidation- Chemical reaction in which an element or comound gains oxygen, or an atom or ion loses electrons.

Salt does nopt cause rusting but speeds up process.

Aluminium does not corode easily - it has a thin natural layer of aluminium oxide, and has a lower density than iron or steel.

Iron has physical properties ideal for manufacture of cars. Aluminium and plastic are easier to recyle and used in cars to reduce weight, better fuel consumption and resist corrosion. Aluminium more expensive than steel (alloy of iron)

Dense - large mass in proportion to volume

Density -Relationship between mass and volume.

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C2 e Ammonia

140 million tons manufactured in world each year. It is gas with sharp smell, used for cleaning fluids explosives and in fertilisers. 80% amonia produed used in fertilisers.Fertilisers - substances applied to soil to replace minerals- improve crop size-

Ammonia is manufactured in a reversable reaction using nitrogen (air) and hydrogen ( oil or natural gas) using Haber process

(http://scienceaid.co.uk/chemistry/applied/images/habereq.png)

Nitrogen (from air) + Hydrogen = Ammonia

Conditions:

  • 200 atmospheric pressure -high
  • 450 Celsuis temp - Temperature is 450 Celsuis as reversible reactions are endo and exothermic so reaction occurs at acceptable rates
  • Ammonia is an Alkali and can be neutralised by acids to make ammonia salts which an be used as fertilisers
  • e.g. Ammonium Nitrate 
  • NH3 +HNO3 ---- NH4NO3
  • All ammonuim compounds contain NH4
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C2 e Haber Process

The Haber Process is a reversible reaction which occurs in both directions, the reaction reaches a dynamic equilibruim

Haber Process = Exothermic as heat is given out 

  • Exothermic = Low temperature
  • Endothermic = High temperature

Catalyst: 

Powdered Iron Catalyst - Increases rate of reaction without increasing temperature because that would lower the yield. 

Spare heat energy is recycled to maintain temperature of plant

Uses:

  • Fertiliser
  • Explosives
  • Nylon and Nitric Acid
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C2 e Reversible reactions

Reversible reaction= reaction that can go either way so that the products of one reaction act as the reactants of the opposite reaction.

Reactants=  Products in a chemical reaction - written on left hand side of chemical equation      Yield= amount of product made in a reaction

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C2 f Making Salts a

Acidic = PH value less than 7 Alkaline = PH value more than 7  neutral= PH = tp 7

Indicator= Substance changes coloue in solutions with different pH levels

Alkali = soluble base  / Base= substance that neutralises an acid to form a salt and water only.

Neutralisation= reaction of acid with base = neutral solution making a salt and water

Acid  +  base ------- a salt   + water

Acidic solutions contain hydrogen ions H+ Highre concentration stronger acid and lower PH

Alkaline solutions contain hydroxide ions OH-

Ionic equation= Equation that summarises a reaction between ions by showing only the ions that take part in reaction

H+   +  OH-   _______ H2O

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C2 f Making Salts b

Bases and carbonates

BASES     NAME FORMULA ION IN SALT COPPER OXIDE CuO Cu2+ SODIUM HYDROXIDE NaOH Na+ POTASSIUM HYDOXIDE KOH K+ AMMONIA SOLUTION NH4 OH NH4+ CARBONATES     CALCIUM CARBONATE CaCO3 Ca2+ SODIUM CARBONATE Na2CO3 Na+ ACID     HYDROCHLORIC ACID HCI Cl- NITRIC ACID HNO3 NO- SULFURIC ACID H2SO4 SO42- PHOSPHORIC ACID H3PO4 PO43-

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C2 g Fertilisers and crop yields

Fertilisers increase crop production by replacing essential elements used by a previous crop or by boosting levels of such elements. Nitrogen in particluar is needed to build plant proteins, increasing growth.Fertilisers provide plants with the essential chemical elements needed for growth particularly nitrogen, phosphorus and potassium. 

Fertilisers increase crop yields but cause the problem of eutrophication when they're washed into rivers and lakes by rainwater polluting water supplies. Excess fertlisier increases concentration of nitrate or phosphate in water. Algea use these to grow faster rate. they produce green layer on water called algal bloom. This blocks sunlight to other plants in water which die. 

Aerobic bacetria use oxygen, they feed on dead plants and as they respire these bacteria use up the oxygen in the water causing most other living organisms to die.

Most chemical fertilisers are made by the reaction of an acid with an alkali.

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C2 g Fertilisers

Most chemical fertilisers are made by the reaction of neutralising an acid with an alkali.

Nitrogenous fertlisersUrea- ammonium nitrate- ammonium sulfate- ammonium phosphate- Potassium nitrate.

The preparation of a fertiliser in a lab involves the following equipment:

  • measuring cylinder to measure a particular volume of an alkali solution
  • a burette to add acid a little at a time until the alkali has been neutralised
  • a filter funnel to remove solid crystals of fertiliser after evaporating some of the water from the neutral fertiliser solution.

A quantity of alkali is placed in a beaker and a solution of acid is run in until the solution is neutral. This can be measured with a pH meter or by removing samples for testing with universal indicator. 

The neutral solution of salt is evaporated until crystals form. These are filtered out, washed and dried in a warm oven.

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C2 h Chemicals from salt

Chlorine , sodium hydroxide and hydrogen are all useful products of electrolysis of sodium chloride solution. Common salt ( NaCl)

It can be made in a laboratory by the reaction of sodium with chlorine. It is found naturally in large amounts in sea water or in underground deposits. It is obtained either by evaporating sea water or by mining underground deposits.

Brine = concentrated solution of sodium chloride in water.

Solution mining is a continuous process that is safer than sending miners underground. Water is pumped underground and into the salt deposit. Salt dissolves in the water, forming a concentrated salt solution. This is then pumped up to the surface ready for use by the chemical industry. 

Mining for salt can lead to subsidence. This happens when insufficient salt is left underground after mining. The weight of the ground above causes the ground to sink downwards and this subsidence can damage buildings and roads.

Sodium chloride is the raw material for the manufacture of hydrogen, chlorine and sodium hydroxide by electrolysis.

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C 2 h Electrolysis of brine

During electrolysis:

  • chlorine gas forms at the anode (positive electrode)
  • hydrogen gas forms at the cathode (negative electrode)
  • a solution of sodium hydroxide forms.

Chlorine used to make Bleach = substance that removes colouras from dyes by oxidising them.

Oxidation happens at the anode because electrons are lost. Reduction happens at the cathode because electrons are gained. Remember OIL RIG: Oxidation Is Loss of electrons, Reduction Is Gain of electrons.

Sodium ions Na+ and hydroxide OH are also present in the sodium chloride solution. They are not discharged at the electrodes. Instead, they make sodium hydroxide solution.

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C2 h Chemicals from salt b

  • Products of electrolysis of sodium chloride solution
  • Hydrogen = manufacture of ammonia and margarine, used to harden vegetable oils.
    Chlorine used for
  • Kill bacteria in drinking water and swimming pool water
  • make solvents
  • make plastics such as polyvinyl chloride (PVC)
  • make household bleach.
  • Sodium Hydroxide is used to make soap and household bleach.
  • Bleach = usedto clean disinfect toilets, drains and kitchen surfaces. Bleach is made when sodium hydroxide and chlorine react together = sodium chlorate

sodium hydroxide + chlorine → sodium chloride + water + sodium chlorate

2NaOH + Cl2 → NaCl + H2O + NaClO

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