4/5/6 markers

• trend of boiling points in halogens?

  • boiling point increases since relative formula/ molecular mass increase
  • intermolecular forces increase in strength
  • need more energy to overcome intermolecular forces
• explain mg, iron and copper in reaction with HCI?

  • metals to dilute HCl
  • measure temperature change/rate of bubbling/colour change
  • copper shows no reaction shown by no bubbles
  • magnesium bubbles faster than iron and iron forms a colour solution
  • CONTROL VARIABLES
• why is graphite soft and slippery and a good conductor of electricity?

  • macromolecular structure
  • 3 covalent bonds per carbon atom leaving one delocalised electron that is free to move throughout the structure and conduct electricity
  • layered structure or interlocking hexagonal rings with weak intermolecular forces between the layers
  • no covalent bonds between the layers
  • can easily slip over each other andbe used as a lubricant
• equation between potassium and water?


  2K + 2H2O -> 2KOH + H2
• compare structure and bonding of carbon dioxide, magnesium oxide and silicone dioxide?

  • Carbon dioxide and silicone dioxide made up of atoms but magnesium is made of ions
  • silicone dioxide and magnesium dioxide are large structures but carbon dioxide is a smaller structure with weak intermolecular forces
  • all have strong bonds (covalent and ionic)
  • bonds in silicone dioxide are single where silicone makes 4 bonds and oxygen makes 2
  • carbon has 2 double bonds
• what happens when lithium reacts with chlorine?

  • lithium looses one electron leaving it with a +1 charge
  • chlorine gains an electron leaving it ith a -1 charge
  • forms positive and negative charges
• describe what happens when 2 potassium atoms react with one sulfur atom?

  • electrons are passed from potassium to sulfur, each loose one electron forming +1 ions
  • sulfur gains 2 electrons forming -2 charged ions
• describe a practical to identify unknown element using silver nitrate ect?

  • measure temperature change when metal is added to silver nitrate solution
  • the greater the temperature change the greater the reeactivity
  • same conc and mass/moles
• titration..?

  • add potassium hydroxide solution to conical flask
  • add few drops of indicator
  • add sulfuric acid from burrette
  • until colour change/ end point
  • read volume from burrette
• give a reason for..?


  WARMING SOLUTION- to speed up reaction

  REPEAT UNTIL EVERYTHING IS GONE- to ensure all HCI reacts

  FILTER MIXTURE- to remove excess
• crystallizeeee

  1. use magnesium oxide and sulfuric acid
  2. add sulfuric acid to beaker and warm it using water bath
  3. add mgo and stir until it is in excess
  4. filter using filtration process
  5. heat in evaporating dish until crystallisation
  6. let crystals cool and pat dry with paper
• titration pt2?

  • measure volume of acid
  • add indicator and NaOH until colour changes
  • record volume of NaOH added and repeat with other acid
  • compare to see which one is more concentrated
  • use white tile
  • read from bottom of meniscus
  • swirl
  • rough titration for approximate end point
• pipette vs burrette?


  pipette finds exact volume , burette measures variable volume
• why do scientists add excess zinc not excess iodine?


  Zinc is a reducing agent that prevents over-iodination. , to make sure all iodine reacts and so none is left in solution as it cant be filtered off
• why do extra bubbles recorded make no difference?

  they should be collected at the end since only caron dioxide is left over and has same volume as air displaced
• describe collision theory?


  as acid particles are used up concentration decreases so less frequent collisions and rate slows down
• compare structure of ethane with ethene?

  • both hydrocarbons
  • both contain 2 carbon atoms
  • ethane has 6 hydrogen atoms but ethene has 4
  • both have covalent bonds but ethane contains single C-C bond whereas ethene has a double bond
  • both react with oxygen in combustion
  • ethene reacts in bromine water ethanedoesnt
  • ethene can react with hydrogen to produce ethane
• 2 reasons bitumen isnt used as a fuel?

  too viscous and flammable
• conditions for cracking?

  steam, catalysts and a high temperature
• why is cracking used to make smaller hydrocarbon molecules?

  greater demand since more useful for fuels and make polymers
• why is wood better to use than natural gas as fuel?

  wood is renewable and produces same amount of CO2 as the tree absorbs
• 2 fuels burned in pollution?

  carbon dioxide and carbon monoxide
• 2 products formed when hydrocarbon combusts completely?

  carbon dioxide and water
• what is a hydrocarbon?

  contains only hydrogen and carbon
• how is propanoic acid formed?

  oxidation of propanol
• what is formed while burning fuels during a practial?

  caarbon soot which is black and sinks to the bottom due to incomplete combustion
• compare polymerisation vs condensation?

  polymer produced by polymerisation ( one monomer) wheareas polyester made by condensation ( produced from 2 monomers) and produce water. Polyester has ester linkage whereas polymer has repeating units
• chromatography investigation?

  1. draw pencil ( so doesnt smudge) baseline on chromatography paper and place spot of food colouring on line
  2. use suitable solvent like water or ethanol and put both into beaker
  3. make sure solvent is beneath start line
  4. use a lid and wait for solvent to seep up with ink via evaporation
  5. mark solvent front and dry paper
  6. MEASURE DISTANCE BETWEEN START AND SPOT OF INK
  7. MEASURE DISTANCE BETWEEN START AND END OF WATER
  8. measure Rf value
• how to change chromatography results?

  use different solvents
• what is the statinary phase vs mobile phase?

  paper vs water/solvent
• green ink contains more than two compounds, why can you only see 2?

  some are colourless or they have the same rF values
• why do manufacturers use the same amount of ink?

  to keep same shade of colour
• 2 substances that are mixtures?

  air and steel
• explain solvent front?


  solvent moves through paper, different dyes have different soluabiities and attractions to the paper so move different lengths
• what is removed from sea water by desalination?


  salt or sodium chloride
• why is desalinatin only used if there is no potable water?


  expensiveeee
• why is water filtered?

  to remove solids
• why is chlorine gas used to treat water?


  sterilisation
• test for lithium carbonate?

  LITHIUM- crush/dissolve tablet in water or acid , clean a wire and place on it , place into a blue flame observe the flame colour it should be crimson red

  CARBONATE- add HCI to see effervescence and bubbling , bubble gas through limewater turning it cloudy
• finding total mass of dissolved solids in pure water?

  1. weigh evaporating dish and add measured volume of water
  2. weigh them together and heat to evaporate
  3. reweigh until constant mass obtained
  4. subtract dish mass from mass
  5. repeat calculate a mean ignore anomylous results