C3

C3

1. Water

   • Hard Water
     • Needs more soap to form a lather
       • Because it contains dissolved compounds that react with the soap
         • Forms Scum
       • Soapless detergents dont react witht he hard water to form scum
     • Contain Mg 2+ ions or Ca 2+ ions
     • Temporary Hard water - when heated - reacts and forms scale
       • Deposited in kettles etc.
     • Calcium ions are good for teeth & bones and reduce the risk of Heart Disease
   • Removing Hardness
     • Made soft when Mg 2+ ions & Ca 2+ ions are removed
     • Tempory hard water made soft when heated as the Mg 2+ ions & Ca 2+ ions react
     • Can also be removed using sodium carbonate that reacts with the calcium ions to form calcium carbonate
     • Or removed using an Ion exchange column, that swaps sodium ions for Mg 2+ ions & Ca 2+ ions
   • Water treatment
     • The stages of treatment - Not shown in the pictrure; Aluminium sulfate is added to clump small bits of sediment together in the sedementation tank

2. Periodic Table

   • Early Periodic Table
     • They arranged the elements in atomic weight rather than in proton numbers
     • 1863 - Newlands proposed his Law of Octaves
       • It stated there would be similar properties every eigth element
       • Didnt work after the 20 element - Calcium
     • Mendeleev - 1869
       • He left gaps for undiscovered elements
         • This left elements with similar elements
         • When missing elements werer discovered, Mendeleev's predictions were confirmed
   • Modern periodic Table
     • Now aranged in proton number
     • Groups have similar properties as they have the same number of electreons on the outer shell
   • Alkali Metals
     • Group 1
       • 1 electron in outer shell
     • Soft Solids at room temp.
     • Low Density
     • React with Halogens to form salts that are white/colourless
   • Transition Metals
     • Middle of table
     • Malleable & Ductile
     • Strong and dense
     • Often used as alloys for building
   • Halogens
     • Non - Metals & in group 7
     • 7 electrons in outer shell

3. Energy & Fuel

   • Energy Released when oxidation occurs e.g. when food reacts with water
     • Use a calorimeter to Measure this
       • Work out the amount of energy transferred using the equation
         • Q = m c *T
           • Energy Transferred = mass of substance X Specific heat capacity X Temp. change
             • E.G ~ Q=m c *T
               • Q = 200g X 4.2 X 30
                 • Q = 25200 J
                   • = 25.2 KJ
         • * represents delta
   • When we work out the energy transfer in solutions we:
     • Assume it has the same properties of water: 1cm3 = 1g & it has a specific heat capacity of 4.2
       • This stays the same even if a solid is added
   • Energy Level Diagrams
     • An energy level diagram of an exothermic reaction
     • It is exothermic as the energy of the products is less than the reactants
   • Bond Energies
     • It is the energy required to make or break a bond
       • Energy Change is 'Bonds Made' - 'Bonds Broken'
   • Fuel Issues
     • Fossil fuels are running out - new fuels need to be developed
     • Hydrogen - Can be used in fuels cells or burnt in a combustion engine
       • Ads - burns easily, release a large amount of energy per gram, produces no C02 when burnt only water
       • Dis - the supply, storage of the gas, safety problems
       • Fuel cell vehicles need to match normal vehicles in; performance, convienience & costs

4. Analysis and synthesis

   • Positve Ions
     • Flame Test
       • Dip a clean flame test loop in the sample solution. Hold the flame test loop at the edge of a Bunsen burner flame. Observe the changed colour of the flame, and decide which metal it indicates. Clean the loop in acid and rinse with water, then repeat steps 1 to 3 with a new sample
     • Most of the Metal hydoxides are insolouble - Some have colurs and so we can identify them from that
       • The reaction is the ion + sodium hydroxide
       • When excess NaOH is added to AlOH the AlOH precipitate dissolves
   • Negative Ions
     • Carbonate Ions
       • Add HCl to substances if there is a gas produced and it turns limewater milky it contains carbonate ions
     • Halide Ions
       • Add Nitric acid, then silver nitrate
         • Chloride ion - white precipitate
         • Bromide ions = Cream Precipitate
         • Iodide ions = Yellow precipitate
     • Sulphate ions
       • Add dilute HCl, the barium chloride. If white precipitate forms, sulphate ion present.
   • Titrations
     • When an Acid and alkali react, a neutralisation reaction occurs
       • The volumes of acid & alkali that react exactly can be found using titration
     • 1. Use a pipette to add the correct volume of Alkaline to a conical flask
       • Add a few drops of indicator to the alkali
         • Fill a burette with acid. Remove any bubbles by opening the stopcock
           • Record the start measuremnt on the burette & slowly add acid to the solution and swirl the conical flask.
             • When the solution changes colour, close the stopcock and record the reading on the burette. Work out the difference.
               • Repeat for improved reliability

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