Chemistry Unit 1

Chemistry Unit 1

1. C1.2.The Limestone Cycle

   • Limestone is mainly calcium carbonate
     • It can be used to make cement, mortar, glass and concrete
       • These react with carbon dioxide and acid rain water and wear away
     • Calcium oxide
       • quicklime
       • water
       • calcium hydroxide
         • slaked lime
         • Ca(OH)2 (s)
         • dissolve in water
         • calcium hydroxide solution
           • Carbon dioxide turns limewater cloudy
           • Ca(OH)2 (aq)
           • CaCO3
           • bubble in carbon dioxide
           • limewater
         • alkali that can be used in the neutralisation of acids
       • CaO (s)
     • carbon dioxide
     • thermal decomposition
     • Limestone is heated with clay to give cement
       • cement is mixed with sand to make mortar
       • cement + sand + aggregate = concrete
   • other carbonates decompose in a similar way
     • magnesium, copper, zinc, calcium and sodium
   • Carbonates react with acids to produce carbon dioxide
     • A salt and water

2. C1.1- Fundamental Ideas in Chemistry

   • C1.1.1 Atoms
     • Structure
       • Atoms have a central nucleus which is made up of protons and neutrons, and surrounded by "shells" of electrons
       • The relative electrical charges in an atom are
     • substances made up of only one kind of atom are elements
       • Elements in the same group have similar properties
     • no. of protons = no. of electrons
       • atoms have no overall electric charge
     • All atoms of a particular element have the same number of protons
       • atoms of different elements have different numbers of protons
     • no. of protons = atomic number
     • no. of neutrons + protons = mass of atom
   • C1.1.2 The Periodic Table
     • Elements in the same group have the same number of outer electrons
       • This gives them similar properties
     • Group 0 = noble gases
       • unreactive
       • stable arrangement of outer electrons
         • full shell
   • C1.1.3 Chemical Reactions
     • When atoms react together they form compounds
       • Ionic = transfer of shared electrons
       • covalent = sharing of electrons
       • metallic = dropping of surplus electrons to form a sea of de-localised electrons
     • mass of products = mass of reactants

3. C1.3 Metals and their Uses

   • C1.3.1 Extracting metals
     • Ores are economical to extract
       • mined and purified before extraction and purified
       • unreactive metals found as pure metals
         • most found as compounds
           • require chemical reactions to extract
       • copper is extracted from ores through smelting
         • requires heat and energy
         • purified through electrolysis
     • traditional mining is bad for the environment
       • phytomining
         • uses plants to absorb metal compounds and that the plants are burned to produce ash that contains the metal compounds
       • bioleaching
         • uses bacteria to produce leachate solutions that contain metal compounds.
     • extraction through carbon
       • Metals that are less reactive than carbon can be extracted by reacting them with carbon
         • iron oxide + carbon + heat = iron + carbon dioxide
       • Metals that are more reactive than carbon can be extracted by electrolysis
         • requires large amounts of energy so is more expensive
       • Metals that cannot be extracted via carbon are expensive
         • there are lots of stages in the process
         • large amounts of energy are needed
   • C1.3.2 Alloys
     • Iron from the blast furnace contains about 96% iron
       • The impurities make it brittle and so it has limited uses
     • An alloy is a mixture of two or more elements, where at least one element is a metal
       • Alloys contain atoms of different sizes, making it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.
         • most metals we use everyday are alloys as pure metals are too soft
     • Alloys can be designed to have certain properties
       • Low-carbon steels - easily shaped
       • high carbon steels - hard
       • stainless steels - resistant to corosion

4. C1.4 Crude oil and fuels

   • C1.4.1 Crude Oil
     • mixture of lots of compounds
       • Most of these are saturated hydrocarbons (alkanes)
       • can be separated by physical means
   • C1.4.2 Hydrocarbons
     • alkanes
       • saturated
         • CnH2n+2
     • alkenes
       • unsaturated
         • CnH2n
     • fractional distillation
   • C1.4.3 Hydrocarbon fuels
     • All fuels contain sulfur
       • This can be removed
       • This is released into the atmosphere when fuels are burned
     • During combustion the carbon and hydrogen in the fuels are oxidised.
     • biofuels
       • ethanol
       • biodielsel
     • Sulfur dioxide and oxides of nitrogen cause acid rain
       • solid particles cause global dimming

5. C1.5 Other useful materials from crude oil

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