C2

Lithosphere -  Outer layer of the earth

• cold
• rigid
• comrpises the crust and top part of the mantle
• made up of tectonic plates which are less dense than the mantle below

The crust is too thick to drill through, so most of our information about the earth is collected from seismic waves produced by earthquakes and man made explosions

Mantle:

The mantle is the zone between the core and the crust

Its cold and rigid just below the crust

At greater depths it is hot and non-rigid and able to move

The earths core transfers energy, so the temperature of the mantle increases with depth

Convection currents -  slowly move plates

Oceanic crust is denserthan the continental crust ( Subduction occurs )

Plate tectonics:

Scientists now acept plate tectonic theory because:

• It explains a wide range of evidence
• It has been discussed and tested by many scientists

Wegeners theory

He proposed that continents were all joined together in a single supercontinent called Pagnea (1914)

Wasnt accepted at the time by scientists but in 1960s new sea floor spreading evidenve was found. Subsequent research led to Wegener's theory slowly becoming accepted

Magma

It rises through the earth's crust because it is LESS DENSE than the crust, this can cause volcanoes

Magma can have different types of composition causing different types of eruptions

When magma cools quickly it forms small crystals

Rocks

Different types of IGNEOUS rock are formed from LAVA, Ignerous rock has different size crystals  

Iron rich basalt rock comes from runny lava in slower volcanic eruptions. It is an EXTRSUIVE igneous rock as it forms outside the volcano

Silica-rich rhyolite rock comes from thick lava explosive eruptions

Sometimes magma rises towars the surface but never reaches it and cools down slowly undeground which reuslts in large crystals like granite. It is an INTRUSIVE igneous rock as it forms inside

Uses of limestone :

• Steel
• Neutralise acidic soil
• Cement and bricks
• Building rocks
• Paper
• Glass

Limestone is Calcium carbonate (CaCO3)

Raw material                  Building material

Clay                                Brick

Limestone and clay        Cement

Sand                               Glass

Iron ore                           Iron

Alluminium ore               Alluminium

Hardness can be compared by rubbing 2 materials together

Limestone is a sedimentary rock - it is made from soft sediments compressed and cemented together, so limestone is quite soft

Marble is a metamorphic rock - formed when limestone is changed by heat and pressure, and is typically comprised of an interlocking mossaic of carbonat crystals. Marble is harder than limestone because its been baked

Granite is an igneous rock with interlocking crystals - when magma cools it solifies and becase of the interlocking crystals it is very hard

Calcium carbonate is both the chemical name for limestone and marble

Thermal decomposition - A reaction where one substance breaks down on heating to give at least 2 new substances

Calcium Carbonate (Limestone) thermally decomposes when heated

Calcium Carbonate        Calcium Oxide + Carbon Dioxide

CaCO3                                 CaO                    CO2

Cement - made when limestone is heated with clay

Concrete - made by mixing cement, sand and small stones with water

Reinforced concrete - It's a composition material whichhas steel rods or meshes running through it. Composites contain at least 2 materials that can still be distinguished

Concrete is strong under compression (squashing forced) but weak under tension (pulling force)

If heavy loads are applied to a beam,the concrete will bend. This creates tension and compression. The tension cracks the concrete

Reinforced concrete is harder and more flexible than concrete, so it is a better construction material

Impure copper can be purified using electrolysis

ANODE - IMPURE COPPER - POSITIVE

CATHODE - PURE COPPER - NEGATIVE

In the purification of copper, an electrolyte of copper(II) sulfate solution is used

• The positive anode loses mass as the copper dissolves
• The negative cathode gains mass as pure copper is plated onto it

The concentration of the copper(II) sulfate electrolyte stays the same because as the impure copper anode dissolves, pure copper is plated on to the cathode at the same rate

At the anode, the Cu atoms lose electrons to form cu2+ ions. This is called oxidation

The electron half equation is:

At the cathode, copper is plated when cu2+ ions gain electrons. This is reduction.

The electron half equation is:

Electrolysis - Method of breaking up a compound using elctricity

An electrical conductor which carries charge to and from a liquid undergoing electrolysis

Sodium Chloride can only conduct electricity when molten or dissolved as the ions are free to move

Aqueos - Dissolved in water

Advantages of recylcing copper:

• It has a fairly low melting point so the energy cost to melt it is low
• Reduces the need for mining, saving reserves and the environmental problems caused by mining
• It keeps the cost of copper down

Disadvantages of recycling copper:

• The small amounts used in electrical equiptment are difficult to seperate
• Valuable 'pure' copper scrap mustnotbe mixed with less pure scrap, such as solder
• Less copper is mined so there are fewer mining jobs
• The actual seperating process may produce pollution
• A lot of copper is thrown away as it is difficult to persuade people to recycle it

OILRIG!!!

Oxidation is loss, Reduction is gain

Metals:

Haematite - Iron ore

Bauxite - Alluminium ore

Malachite - Copper ore

Some unreactive metals such as gold can be found as the metal itself - chemical seperation is not needed

Alloys:

Alloys - Mixtures containing at least one metal

Some smart alloys return to their original shape after being heated to a certain temperature

Nitinol ( nickel-titanium ) is a smarty alloy which is used to make spectacle frames, it returns to its original shape after being bent if it is put in hot water

Smart alloys are becoming more important as new ways to use them are found

Only IRON and STEEL rust

ACID RAIN and SALT WATER accelerate rusting

Rusting is an OXIDATION reaction because iron reacts with oxygen forming an oxide

Word equation for rusting:

Alluminium does NOT corrode in moist air because it has a protective layer of alluminium oxide which, unlike rust , does not flake off the surface

Different metals corode at different rates

Alluminium in car bodies and wheel hubs - Does not corrode, low density, malleable, quite strong

Iron or steel in car bodies - Malleable, strong

Copper in electrical wires - Ductile, good electrical conductor

Lead in lead-acid batteries - Chemical reaction with lead oxide produces electricity

Plastic in dashboards , dials, bumpers - Rigid, does not corrode, cheap

PVC in metal wire coverings - Flexible, does not react with water, electrical insulator

Glass and plastic/glass composite in windscreens - transparent shaterproof (may crack)

Fibre in seats - can be woven into textiles, can be dyed, hard-wearing

Alloys - Mixtures of elements containing at least one metal; and often have different and more useful properties than the metals they are made from

E.g.

• Steel is harder and stronger than iron
• Steel is less likely to corrode than iron

Advantages of Alluminium:

• Lighter
• More resistant to corrosion than steel

Advantages of Steel

• Costs less
• Stronger

Lighter alluminium body improves fuel economy as it corrodes slowly so car body lasts longer

Advantages of recycling materials from old cars:

• Less mining saves finite resources needed to make metals
• Less crude oil is needed to make new plastics
• Less waste means less landfill
• Fewer toxic materials, such as lead from batteries, are dumped

Disadvantages of recycling materials from old cars:

• Fewer mines are built and fewer mining jobs created
• Difficult to seperate the different materials
• Some seperating techniques produce pollution
• Some recylcing processes are very expensive

World food production depends on NITROGEN FERTALISERS - These are made from ammoia

Ammonia is made by the Haber process

Word equation for The Haber Process:

Balanced symbol equation:

The optimum (best) conditions for the Haber process are to:

• Use a Catalyst made of Iron
• Raise the temperature to about 450 degrees (which is fairly low for an industrial process)
• Use high pressure ( about 200 atmospheres )
• Recycle any unreacted nitrogen and hydrogen

How do the conidions used make the process as efficient as possible:

• The IRON CATALYST increases the rate of reaction (rate of successful collisions) but not the percentage yield
• HIGH PRESSURE increases the percentage yield of ammonia
• HIGH TEMPERATURE increases reaction rate and breaks down ammonia, reducing percentage yield
• The yield isnt very high but the rate is fairly quick

The Catalyst

The catalyst has NO affect on the posiion of equilibrium and doesnt produce any greater percentage of ammonia, it is there to simply SPEED UP THE REACTION

In the abscence of a catalyst the reaction is so slow virtually no recation takes place in a sensible time

What effects the cost of chemical manufacture:

Costs INCREASE when the PRESSURE is raised (increasing the plant costs) and the TEMPERATURE is raised (increasing energy costs)

Costs DECREASE when a catalyst is used, unreacting starting materials are recycled and automation is used (reducing wage bills)

These economic considerations determine the conditions used to manufacture a chemical

• Both the reaction rate and the percentage yield must be high enough to give a sufficient daily yield of product
• A low percentage yield can be accepted if the reaction can be repeated many ti es with recycled starting materials
• Optimum conditions give the lowest cost, rather than the fastest rates or highest yields

Metal oxides and metal hyroxides are bases

Alkalis - bases that are soluble in water, e.g. sodium hydroxide and calcium hydroxide

Neutralisation - leaves no H+ ions:   H+  +   OH-          H20

Takes place when an acid and a base react together to make a salt and water

Acid + base       Salt + water

Indicators - show a sudden colour change at one PH value

Universal inicator - Shows a gradual range of colour changes as it contains a mixture of different indicators

In solution ALL acids contain H+ ions ( hydrogen ions ).  Alkalis contaom OH- ions (hydorxide ions)

The PH of an acid is determined by the CONCENTRATION of H+ ions-Higher conc lower PH

Acids react with bases and metal carbonates to form salts

Word equations:

Acid + Base       Salt + Water

Acid + Metal carbonate     Salt + water +carbon dioxide

Salts names have 2 parts, 2nd part shows which acid it has been made from

Sulfuric - Sulfate

Nitric - Nitrate

Hydrochloric - Chloride

Phosphoric - Phosphate

Word equation between hydrochloric acid and copper carbonate:

Symbol equation for the reaction between hydrochloric acid and copper carbonate is:

Salt is maintained by:

• Evaporation
• Mining (blasting and digging) - Hot water is pumped down and brine is pumped back up

Farmers use fertalisers to increase their crop yields

These fertalisers must be dissolved in water before they can be absorbed by the plant roots as only dissolved substances are small enought to be absorbed

Fertalisers are needed as the world population is rising and there is a greater demand for food production from the lad available

Fertalisers increase crop yield by:

• Replacing essential elements that are used by the previous crop or providing extra essential elements
• Providing nitrogen that is incorporated into plant protein resulting in increasded growth

Nitrogen - helps stalks and leaves grow

Phosphorous - Speeds up the growth of roota and the ripening of fruit

Potassium - Protects against disease and frost damage, promotes seed growth

Fertalisers cause problems if they get into ponds, lakes and rivers.

Fertalises encourage algae growth, leading to eutrophication

Eutrophication happens when:

• Sunlight reaches plats at the bottom of the water that photosynthesise and produce oxygen
• Fertalisers are washed off fields
• Fertalisers in the water increase the nitrate and phosphate levels in ponds, lakes and rivers
• Algae grow quickly on the surface (algal bloom) because of dissolved fertalisers
• The algae block off the sunlight to other oxygen-producing plants which die
• Aerobic bacteria use up the oxygen in the water and feed on the dead and decaying plants
• Most living organisms die due to the lack of oxygen

Excessive use of fertalisers pollutes water supplies

Many fertalisers are SALTS, so they can be made by reacting an ACID and an ALKALI to make salt and water

e.g. Sulphuric acid + ammonia        Ammonia sulfate

H2SO4 + 2NH3         (NH4)2SO4

A fertaliser would be produced by combining nitric acid and ammonia solution to give ammonium nitrate

The process of producing a fertaliser from an acid and alkali is:

• The alkali is TITRATED wih the acid using an indicator to find out the quantities needed before the main batch is made (this is repeated until the results are consistent)
• Although the acid and alkali have now reacted completley to producea neutral solution of ammonium sulfate fertaliser, this is contaminated with indicator soultion
• The titation results are used to repeat the experiment using the correct quantities
• The dissolved fertaliser is heated to evaporate most of the water off, then left for the remaining solution to crystalize. The cystals are then filtered off

Salt is mined in 2 different ways:

• Mining it from the ground as rock salt
• Solution mining by pumping in water and extracting saturated salt solutions

Mining salt can lead to SUBSIDENCE

The ground above a mine can sink causing landslips and destroying homes

Salt at the surface, particularly brine solution, can escape and affect habitats

Concentrated sodium chloride soiltion (brine) can be seperated by electrolysis

HYDROGEN is made at the NEGATIVE CATHODE

CHLORINE is made at the POSITIVE ANODE

SODIUM HYDROXIDE forms in solution

HYDROGEN and CHLORINE are reactive so it is important to use inert electrodes so that the products dont react before they are collected and the electrodes do not dissolve

NaCl

During the electrolysis of NaCl solution:

• Na+ and H+ ions migrate to the negative cathode, Cl- and OH- migrate to the positive anode
• At the cathode, hydrogen is made - electrons are gained so this is reduction as shown in this half equation:

At the anode, CHLORINE is made - electrons are lost so this is oxidation

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The ions not discharged make SODIUM HYDROXIDE SOLUTION

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Chlori-alkali industry

Sodium hydroxide and chlorine are used to make household bleach

Chlorine and sodium hydroxide are important raw materials. They are involved in making about half the chemicals we use on a daily basis including solvents, plastics, paints, soaps, medicines and food additives