chemistry paper 1

• anode (+)

  the gas produced at the anode is always oxygen except if a halide is present

  chlorine forms chloride

  bromine forms bromide

  iodine forms iodide
• cathode (-)

  hydrogen is produced if the metal is more reactive than hydrogen

  if the metal is less reactive than hydrogen then the metal is produced
• half equation when a halide isn't present

  4OH¯ - 4e¯ --> O₂ + 2H₂O
• test for oxygen

  a glowing splint is inserted into a test tube of the gas, the splint relights
• test for chlorine

  damp litmus paper is put into the gas, if chlorine is present the litmus paper is bleached and turns white
• test for hydrogen

  a burning splint is held at the top end of the test tube full of gas, if hydrogen is present then the splint burns rapidly with a pop sound
• titration method (part 1)

  1. use the pipette to put 25cm³ of alkali solution into a conical flask that is on a tile
  2. use a small funnel to carefully fill the burette with acid to the 0cm³ line
  3. put 5-10 drops of indicator into the conical flask and swirl it into the alkali
  4. carefully open the tap of the burette so acid flows into the flask at a drop by drop rate whilst swirling
  5. look for a colour change in the indicator
• titration method (part 2)

  1. when the colour change is lasting longer and it closer to being permanent, slow the drops down
  2. stop adding the acid after a single drop causes the colour to completely change
  3. read the scale on the biuret and record the volume of acid added
  4. repeat this method 2 more times and calculate a mean discounting any anomalies
• converting cm³ to dm³

  ÷1000
• converting dm³ to cm³

  x1000
• moles = mass ÷ Mr
• concentration = mass ÷ volume
• atom economy = relative formula mass of desired product ÷ relative formula mass of all products x100
• percentage yield = mass of product actually made ÷ maximum theoretical mass of product x100
• plum pudding model

  a ball of positive charge with negative electrons embedded in it
• alpha particle scattering experiment 


  shot alpha particles at a thin sheet of gold

  most particles passed straight through

  a small amount were deflected back
• rutherford's nuclear model 


  tiny, positively charged nucleus in the centre where most of the mass is concentrated

  a 'cloud' of negative electrons surrounding the nucleus

  most of the atom was empty space
• bohr's nuclear model

  electrons orbited the nucleus in fixed shells fixed distances away
• why are group 1 metals more reactive as you go down the group?

  more shells as you go down so larger atomic radius

  weaker attraction between the nucleus and outer electron

  so the outer electron is lost easier
• properties of group 1 metals

  soft(er)

  low(er) density

  low(er) melting and boiling point

  can conduct heat and electricity

  very reactive

  form white compounds
• transition metal properties

  hard(er)

  strong(er)

  high(er) density

  high(er) melting and boiling point

  can conduct heat and electricity

  unreactive

  used as catalysts

  form coloured compounds
• why are group 7 elements more reactive as you go up the group?

  less shells so smaller atomic radius

  stronger attraction between the nucleus and incoming electrons
• fluorine colour

  pale yellow gas
• chlorine colour

  green gas
• bromine colour

  orange/brown liquid
• iodine colour

  grey/black solid and purple vapour
• diamond

  covalent bonds hold the molecules together

  these bonds are very strong

  they are hard to break

  very high melting point

  hard
• why is diamond hard?

  each carbon is bonded to 4 other carbon atoms

  with strong covalent bonds

  in a giant covalent structure

  which need a lot of energy to overcome the bonds
• why does diamond have a very high melting point?

  many strong covalent bonds

  between the carbon atoms

  in a giant structure

  needs a lot of energy to overcome the bonds
• graphite

  arranged in hexagonal layers that can slide

  soft

  weak intermolecular forces between the layers

  conducts electricity because it has delocalised electrons that can move and carry charge through the structure
• why is graphite soft?

  each carbon is bonded to 3 other carbon atoms

  hexagonal layers have weak intermolecular forces between them

  so the layers can slide
• why can graphite conduct electricity?

  each carbon is bonded to 3 other carbon atoms

  each carbon has a delocalised electron

  which can move and carry charge

  through the structure
• graphene & fullerenes

  graphene is 1 atom thick

  can conduct as it has delocalised electrons that are free to move and carry charge through the structure

  buckminsterfullerene's are useful as lubricants and for drug delivery
• metallic bonding 


  electrostatic forces of attraction between the positive metal ions and delocalised outer electrons

  they are strong

  hard to break

  high melting point

  can conduct electricity
• why alloys are hard but pure metals are soft

  pure metal atoms are arranged in layers that can slide

  alloys have different sized atoms

  so the layers can't slide
• why any metal (ide) has a high melting point?

  it has a giant lattice structure

  with strong electrostatic forces of attraction between 2 oppositely charged ions

  so it needs a lot of energy to overcome them