The lithosphere is the outer layer of the Earth and is cold and rigid
This comprises of the crust and top of the mantle
The mantle is between the core and crust. The crust transfers energy so the temperature of the mantle increases with depth
The Earth has an iron core
Plate tectonics:
A plate is a section of the lithosphere, which is moved by convection currents in the mantle
Plates move at around 2.5cm per year
Wegner's theory of continental drift was published in 1914 and evidence of sea floors spreading was found in the 1960s
Oceanic crust is more dense than continental crust - collision of these leads to subduction and partial melting
Plates are cooler at ocean margins so they sink and pull plates down
Raw materials:
Clay is used to create brick, limestone and clay creates cement, glass is made from sand, and metals are prepared from ore
Types of rock:
Igneous rock is created from magma. Example: granite, basalt (iron-rich), formed by runny lava, or rhyolite (silica-rich), formed by thick lava
Sedimentary rock is made of soft layers cemented together. Example: limestone - (calcium carbonate), which thermally decomposes to calcium oxide and carbon dioxide (CaCO3 → CaO + CO2)
Metamorphic rock is formed when limestone is heated and under pressure. Example: marble
The size of crystals in igneous rock is related to the rate of cooling of molten rock
Magma is molten rock beneath the surface and lava is molten rock at the surface
Some volcanoes erupt runny lava, but some erupt thick lava, explosively
Concrete and cement:
Calcium carbonate (limestone) thermally decomposes, yielding two substances, calcium oxide and carbon dioxide, when heat is applied)
The symbol equation for this is CaCO3 → CaO + CO2
Reinforced concrete is a composite (it contains steel rods and concrete). Steel rods prevent the concrete from cracking under tension
Copper mining:
Copper can be extracted by heating its ore with carbon
Extracting copper with electrolysis:
Electrolysis can be used to purify copper. Recycling it this was reduces the need to mine it from the ground and pollution is therefore lower
A diagram of the process is shown below. At the anode (+), copper atoms lose electrons, creating Cu2+ ions. At the cathode (-), copper atoms gain electrons. Here are the electron half equations: At the anode (+): Cu - 2e- → Cu2+, this is oxidation (loss of electrons) At the cathode (-): Cu2+ + 2e- → Cu, this is reduction (gain of electrons)
Impure copper is the anode and pure copper is the cathode. Copper(II) sulfate solution is the electrolyte
Alloys:
Alloys are a mix of multiple metals, such as brass (copper and zinc, used for coins, door decorations, musical instruments), solder (lead, tin, to join electrical wires) and amalgam (mercury, silver, tin and other metals, used for filling teeth)
Smart alloys, such as nitinol (nickel and titanium), used for spectacle frames, returns to its original shape once in hot water
Rusting:
Both steel and iron can rust when it reacts with oxygen and water: iron + oxygen + water → hydrated iron(III) oxide. The process is sped up with salt or acid rain
Aluminium vs steel vs iron for cars:
Aluminium is light, improving fuel economy and more resistant to corrosion than steel. It has a layer of aluminium oxide
However, steel is both cheaper and stronger
Iron is more dense than aluminium, and is magnetic. It rusts easily. Both iron and aluminium are both malleable and both good conductors
Glass, plastics, fibres, steel and aluminium are the main materials used to build a car
There is a law on the minimum percentage of recycled metal required in new cars
The Haber process:
The Haber process creates ammonia for use in fertilisers, cleaning products and other chemicals (e.g. nitric acid). It uses nitrogen from the air and hydrogen from cracking oil fractions or natural gas
It consists of a reversible reaction at equilibrium: N2 + 3H2 ⇌ 2NH3
The optimal conditions are: iron catalyst, 450 °C temperature, high pressure (200 atmospheres)
Although higher temperatures reduce yield, this increases the speed of the reaction and unused nitrogen and hydrogen is recycled in the process so there is no loss
Neutralisation:
A neutralisation reaction is between an acid and base, resulting in salt and water near to pH 7
acid + base → salt + water
All acids contain H+ ions and alkalis contain OH- ions, neutralisation leaves no free H+ ions
Universal indicator is a mix of many indicators for a gradual colour change
Litmus is a pH indicator which is red in low pH acids and blue in high pH alkalis
A base is a chemical with a pH greater than 7. An alkali is a type of base where OH- ions are present, a soluble base
Carbonates are types of base, when reacted with an acid the products are carbon dioxide, water and a salt
Salts:
Acids, bases and a metal carbonate react to form salts: acid + metal carbonate → salt + water + carbon dioxide. Salt names have two parts, the second shows the acid it was made from (eg 'sulfate' for a salt made with sulfuric acid)
A symbol equation for the reaction of hydrochloric acid and copper carbonate is: HCl + CuCO3 → CuCl2 + H2O + CO2
Fertilisers:
Fertilisers increase crop yield by containing essential elements and providing nitrogen, which increases growth
They must be disolved to be absorbed by the plant. Some fertilisers are slow release (they dissolve slowly)
The three essential elements needed for growth are nitrogen (N), phosphorus (P) and potassium (K)
Eutrophication:
Eutrophication destroys most plants and animals in a river, lake or pond and is caused by fertilisers. Here are the involved steps:
Fertilisers wash into the water
Fertilisers increase nitrate and phosphate levels in ponds, causing algae to grow quickly on the surface (an algal bloom)
Algae blocks off sunlight to oxygen producing plants in the water, causing them to die and stop producing oxygen
Aerobic bacteria use up all the oxygen in the water and feed on dead plants
Most animals in the body of water die
Making a sample of a fertiliser:
Most fertilisers are salts, so acid + base → water + salt
First, the alkali is titrated with the acid using an indicator to find the correct quantities required
Now a neutralised solution of fertiliser is formed, but this is contaminated with the indicator solution. Therefore, this titration is repeated, this time without the indicator, to get the batch of fertiliser
This is then heated to evaporate the water and left to crystallise. These crystals are finally filtered off
Ammonium sulfate fertiliser would be made with sulfuric acid and ammonia, ammonium nitrate is made with nitric acid and ammonia
Salt (sodium chloride - NaCl) mining:
Rock salt can be mined from the ground, or water can be pumped in and the saturated salt solution extracted to get salt
This can lead to landslips, and salt at the surface can escape, causing damage to wildlife
Electrolysis can be used to seperate concentrated sodium chloride (brine). Hydrogen gas is made at the cathode (-) and chlorine gas is made at the anode (+). A sodium hydroxide solution forms. At the cathode: 2H+ + 2e- → H2, at the anode: 2Cl- - 2e- → Cl2
A chemical test for chlorine is litmus paper, which is bleached if it is present
Sodium chloride can be used as a preservative or a flavouring. It is also a good source of chlorine and sodium hydroxide and can be used to make household bleach, PVC and solvents. Chlorine is used to sterilise water and to make solvents, household bleach and plastics. Hydrogen is used in the manufacture of margarine. Sodium hydroxide is used to make soap
Household bleach, sodium chlorate (NaClO) is made when sodium hydroxide and chlorine react together
