GCSE CHEM - PAPER 1 ALL CONTENT

• Covalent bonds


  Electrostatic attraction between a shared pair of electrons and the positively charged nuclei of the atoms in the bond
• Properties of ionic compounds

  Between a metal and a non-metal

  Giant structure - millions of ions

  Strong electrostatic attractions between the positive and negative ions = high melting and boiling points

  Dissolve in water

  Conduct electricity when in liquid form or molten
• Properties of small molecules

  Have weak intermolecular forces = easy to break molecules apart from eachother = low melting points

  Usually gases or liquids at room temperature

  Do not conduct electricity as all electrons are used up in covalent bond
• Giant covalent structures


  All atoms are linked to other atoms by strong covalent bonds, which require lots of energy to overcome to melt or boil
• Properties of metals


  Giant structures

  Atoms held together by strong metallic bonds = high melting and boiling points

  Malleable (can be bent into shapes)

  Ductile (Can be drawn into wires)
• moles equation

  mass / mr
• Volume equation (incl moles and conc)

  Volume = mass or moles / concentration
• Percentage yield

  Actual yield / theoretical yield x 100
• Atom economy

  Mr desired product / Mr all reactants x100
• Moles (incl vol and 24dm3)

  Moles = vol(dm3) / 24dm3
• Centimeters cubed to decimeters cubed

  1cm3 = 0.001dm3
• metal + water

  metal hydroxide + hydrogen
• All reactions between acids and metals are REDOX reactions
• acid + metal oxide


  salt + water
• acid + metal hydroxide


  salt + water
• acid + alkali 


  salt + water
• acid + metal carbonate


  salt + water + carbon dioxide
• metal + acid


  salt + hydrogen
• Pipette


  Measures fixed volume of solution with unknown concentration
• Burette


  Measures volume of solution with known concentration
• Making soluble salts


  React acid with an excess of metal, metal oxide, hydroxide or carbonate until no more reacts

  Filter mixture to get a solution of the salt with the excess solid left behind

  Heat solution to start evaporating water from solution

  Turn off heat and leave until all water is evaporated, leaving solid salt behind
• Measuring energy changes in reactions (neutralisation between HCl and NaOH)

  Add increasing volumes of NaOH solution to HCl and record maximum temperature reached in each experiment

  Use a measuring cylinder to measure 30cm3 of dilute HCl

  Transfer acid to polystyrene cup

  Use thermometer to measure temperature of acid

  Use measuring cylinder to measure 5cm3 of sodium hydroxide solution

  Transfer to polystyrene cup, fix a lid and insert thermomter and stir

  Increase volume of sodium hydroxide by 5cm3 each time you repeat
• Titration purpose

  Investigate how much acid is needed to neutralise a known volume of alkali or vice versa
• Titration practical

  Add known volume (25cm3) of alkali into conical flask

  Fill burette with acid and record initial reading

  Add few drops of indicator

  Open tap to add acid to flask, swirling regularly until indicator changes colour = end point
• Phenolpthalein

  Acid - colourless

  Alkali - pink
• Methyl orange

  Acid - red

  Alkali - yellow
• Concordant results

  Within 0.1cm3 of eachother
• Exothermic reaction profiles

  Reactants have more energy than products

  
• Endothermic energy profile

  Reactants have less energy than products

  
• Activation energy

  From reactants line to peak
• Overall energy change

  From reactants line to products line
• Energy change in a reaction = tot energy needed for breaking bonds - tot energy making bonds
• If overall energy change is negative, reaction is exothermic
• If overall energy change is positive, reaction is endothermic
• Simple chemical cell involves 2 metals with different reactivity dipped into a salt solution

  Electrons flow from negative electrode to positive electrode
• Hydrogen fuel cell advantages

  Only waste product is water

  Can be a range of sizes

  Don't need to be recharged using electricity
• Hydrogen fuel cell disadvantages

  Hydrogen gas is very flammable

  Difficult to store / compress

  Hydrogen gas may be derived from non renewable sources
• Hydrogen fuel cell reaction

  2H2 + O2 -> 2H2O

  Oxidation of hydrogen produces a pd