The Earth's Structure
Lithosphere = the Earth's crust and top part of the mantle.
Mantle = the zone between the core and the crust.
Subduction happens when an oceanic plate meets a continental plate. The denser oceanic crust sinks below the continental.
Wegner's continental drift theory (1914) = All continents were once one piece of land but drifted apart due to convection currents in the mantle.
Since then, new evidence has come to light and the theory is now more widely accepted.
Magma rises up through gaps in the Earth's crust, leading to volcanoes. Igneous rock is formed from the lava (eg. basalt, rhyolite).
Over time, layers build up over this rock compressing it and forming sedimentary rock (eg. limestone).
This is put under further pressure, heated as it gets closer to the mantle, creating metamorphic rock (eg. marble).
Calcium carbonate (limestone) thermally decomposes when heated;
Calcium carbonate -> calcium oxide + carbon dioxide
Cement is made when limestone is heated with clay.
Concrete is made by mixing cement, sand, stones and water.
Reinforced concrete is a composite material which had steel rods running through it.
Concrete is strong under compression but weak under tension. Putting a steel rod/mesh in the concrete stops it from cracking under tension.
Alloy = mixture containing at least one metal.
Amalgam, which contains mercury, is used for fillings. Mercury is toxic, but amalgam is not.
Smart alloys return to their origninal shape when heated to a certain temperature.
Nitinol is a smart alloy used for glasses frames. It returns to its original shape if put in hot water.
Electrolysis of Copper
Electrolysis is used to purify impure copper so it can be recycled.
Electrolyte: copper (III) sulphate solution
Anode: impure copper
Cathode: sheet of pure copper
As the impure copper dissolves, the pure copper is plated on the cathode, so the concentration of the solution is always the same.
Anode: Cu - 2e⁻ -> Cu2+
Cathode: Cu2+ + 2e⁻ -> Cu
A pile of impurities collects underneath the anode.
Iron and steel rust, whereas other metals corrode. Acid rain and salt water accelerate rusting.
Iron + oxygen + water -> hyrated iron (III) oxide
Car bodies are built of aluminium or steel. Steel costs less and is stronger, whereas aluminium is lighter and more resistant to corrosion.
Copper is used in electrical wires because it is ductile and a good conductor.
Glass and plastic/glass composite materials are used in windscreens because they are transparent and shatterproof.
Recycling materials from old cars means that less finite resources such as crude oil are used to make new materials. However, some recyling processes can be very expensive and the lack of mining means that there are less available jobs.
High pressure = ^ % yield, but expensive.
High temperature = ^ROR, decreased % yield, also expensive.
Catalyst speeds up the ROR.
Neutralisation and Salts
Acid + Base -> Salt + Water
Acids contain H+ ions.
Alkalis contain OH- ions.
H+ + OH- -> H2O
Acid + Metal Carbonate -> Salt + Water + Carbon Dioxide
The second part of the salt name is determined by the acid used.
Sulphuric acid = sulphate
Nitric acid = nitrate
Hydrochloric acid = chloride
Phosphoric acid = phosphate
eg. hyrochloric acid + copper carbonate -> copper chloride + water + carbon dioxide
- Fertilisers are washed off fields
- They enter the water and cause an increase in nitrate and phosphate levels
- This encourages algae growth, creating an algal bloom
- The algae block off sunlight to other organisms
- Plants are unable to photosynthesise and die
- Decomposers use up the oxygen in the water
- All the other organisms are starved of oxygen and die
Fertilisers increase the crop yield by replacing lost essential elements in the soil.
The nitrogen encourges increased plant growth.
Salt is mined by removing it from the ground as rock salt, or pumped up from the ground as solution mining. Mining can lead to subsistence.
Anode = chlorine made, Cathode = hydrogen made. Sodium hydroxide solution is left behind.