Chemistry C1.3-1.4

Chemistry C1.3-1.4

1. C1.3

   • Extracting metals
     • Rock containing enough metal to make it worth extracting is an ore
       • Mining ores often involves digging up large amounts of rock.
       • The ore may need to be concentrated before being extracted
         • This can produce high amounts of waste and impact the environment
   • Iron and steels
     • Many ores used to produce iron contain iron(lll)oxide.
       • Iron(lll)oxide is reduced at heat in a blast furnace using carbon
         • Iron produced contains 96% iron, impurities make it hard and brittle so it has few uses as cast iron
       • Amounts of carbon and other elements are carefully adjusted when making steel. Low-carbon steels are easily shaped and high-carbon steels are hard
         • Stainless steels, contain larger quantities of other metals. They resist corrosion
     • Most iron is used to make steels. Steels are alloys of iron as they are mixtures of iron, carbon and other elements. Alloys can be made so they have properties for specific uses
   • Aluminium and titanium
     • Aluminium has a low density and is resistant to corrosion
       • More reactive than carbon so it can't be displaced using carbon
         • Must be extracted using electrolysis of molten aluminium oxide. Requires high temp and lots of electricity. Makes it expensive to extract
     • Titanium is resistant to corrosion and is strong. Low density
       • Titanium oxide can be reduced by carbon, but the metal reacts with carbon making it brittle
         • Extracting titanium is expensive
   • Extracting copper
     • Copper can be extracted from ores using smelting, this is heating the ore in a furnace
       • This produces impure copper, which electrolysis can purify
         • This needs huge amounts of heat and electricity, it's very expensive
     • Phytomining uses plants to absorb copper compounds from the ground. Plants are burned and produce ash from which copper can be extracted
     • Bioleaching uses bacteria to produce solutions containing copper compounds
   • Metallic issues
     • Mining for ores involves digging up and processing large amounts of rock. This produces lots of waste and can harm the environment
     • Benefits of metals in construction: Strong, Can be bent into shape, can be made into flexible wires, good electrical conductors
     • Drawbacks of metals in construction: Obtaining metals from ores produces pollution and uses limited resources, metals are more expensive than materials like concrete, iron and steel can rust

2. C1.4

   • Fuels from crude oil
     • Crude oil contains many different compounds that at different temps. they burn under diff conditions so crude oil needs to be separated to make useful fuels
       • Distillation is used to separate mixtures of liquids. Simple distillations of crude oils can produce liquids boil within different temps. these liquids are called fractions
         • Most of the compounds in crude oil are hydrocarbons. Their molecules contain only hydrogen and carbon. Many hydrocarbons are alkanes, alkanes contain as many hydrogen atoms as possible and are known as saturated hydrocarbons
   • Fractional distillation
     • Crude oil is separated at refineries
       • The boiling point of a hydrocarbon depends on the size of its molecule. the larger it is, the higher the boiling point
         • The crude oil is vaporised and fed into a fractionating column. It is hot at the bottom and gets cooler towards the top.
           • In the column there are trays with holes to allow gases through. Vapours move up the column getting cooler. The hydrocarbons condense to liquids when they reach their boiling point
             • Hydrocarbons with smaller molecules have lowest boiling points and are collected at the top. Fractions with low boiling points are less viscous so they are runny, they are also flammable
   • Burning fuels
     • When pure hydrocarbons burn totally they are oxidised to CO2 and H2O
       • In a limited supply of air, incomplete combustion produces carbon monoxide, carbon may be also produced. Solid particle that contain soot and particulates are produced
     • Most fossil fuels contain sulfur compounds. When fuel is burned the compounds produce sulfur dioxide. this causes acid rain
       • At high temps produced when fuels burn, oxygen and nitrogen may combine to form nitrogen oxides. this also causes acid rain
   • Cleaner fuels
     • Burning fuels releases substances that spread through the atmosphere, affecting the environment
       • Burning any fuels containing carbon produces CO2, scientists believe CO2 causes global warming. carbon monoxide produces tiny solid particulates that reflect sunlight and cause global dimming
         • Sulfur dioxides are removed by power stations. exhausts of cars are fitted with catalytic converters to remove carbon monoxide and nitrogen oxides
   • Alternative fuels
     • Biofuels are made from plant or animal products and are renewable. Biodiesel is made from vegetable oil
     • Biodiesel contributes little to CO2 levels. However plants grown for biodiesel use large areas of farmland
     • Ethanol is a biofuel. It can be stored and distributed like other liquid fuels. it can be mixed with petrol