Paper 1 - Atomic Structure and The Periodic Table

• What is filtration?


  The process of separating an insoluble solid from a liquid.
• What does insoluble mean? 


  A solid that will not dissolve in a liquid.
• Filtration practice


  • Use a conical flask
  • Place a filter paper into a filter tunnel that goes directly into the conical flask
  • Start to pour the mixture into the filter system
  • Should leave the solid in the filter paper, and water into the conical flask
• What are Filtration, Crystallisation, Distillation and Chromatography used for and can only be used for?


  Mixtures
• What is Crystallisation? 


  The process of separating a soluble solid from a liquid.
• What does soluble mean? 


  A solid that can dissolve in a liquid.
• Crystallisation practice


  • You could leave the liquid in the mixture to evaporate for a few days leaving the solid left.
  • Gently heating the solution, however you have to be careful as certain chemicals can break down as heated.
• What does an aqueous solution (aq) mean? 


  Dissolved in water.
• Set up for Simple Distillation 


  1. Place solution with the liquid and dissolved solid into flask.
  2. Flask connected to continuous glass tube.
  3. Glass tube surrounded by jacket called the condenser.
  4. Cold water from tap continuously runs through the condenser keeping internal glass tube cold (After running through condenser tap water goes down sink).
  5. Thermometer part of apparatus.
  6. Liquid should end up into the beaker.

  
• Simple distillation practice 


  • Start by heating the solution (e.g bunsen burner).
  • As solution is heated, the liquid will start to evaporate turning into a vapour.
  • This rises up the glass tube.
  • The thermometer reading increases.
  • Heat solution until it boils
  • Vapour passes through condenser, vapour should now be condensed, turning back into a liquid
  • This liquid will now be collected into the beaker.
  • Crystals of our solid left in the flask, and liquid in our beaker.
• What is fractional distillation? 


  It is the process to separate a mixture of different liquids, which must have different boiling points.
• Fractional distillation apparatus


  1. In the flask, there is a mixture of two or more different liquids.
  2. As long as the liquids have different boiling points, fractional distillation will work.
  3. Next is the fractionating column, hundreds of glass beads fill this column.
  4. Then everything is the same as the Simple Distillation apparatus.

  
• Why does Liquid A (80°C) evaporate more easily than Liquid B (100°C) during fractional distillation?

  Because Liquid A has a lower boiling point
• What happens to the vapours when they reach the fractionating column during fractional distillation?


  • Vapours condense
  • Drip back into the flask
  • Evaporate again
  • The chemical will the lowest boiling point will will rise ahead of the HBP
• What does it indicate when the temperature rises on the thermometer during fractional distillation?


  It indicates that a mixture of the two different vapours is passing over the thermometer
• What is the significance of the temperature stopping rising during fractional distillation?


  It indicates that the lower boiling point chemical is being collected
• What occurs after the first proper fraction is collected in fractional distillation?


  • The temperature on the thermometer begins to rise again
  • A mixture of vapours is passing through the condenser
  • Mainly contains the higher boiling point chemical
• What does it mean when the thermometer reaches a constant temperature of the HBP during fractional distillation?

  It means a relatively pure sample of Liquid B is being collected
• All separation techniques are physical processes, what does this mean?


  This means they do not involve chemical reactions and no new substances are made.
• What does Paper Chromatography allow us to do? 


  It allows us to separate substances based on their different solubilities.
• What is the first step in paper chromatography practice?


  Draw a horizontal pencil line about 1 cm high from the bottom of the chromatography paper.
• What should you do after placing a small spot of the coloured mixture on the pencil line?


  Allow it to dry.
• Why must the solvent not cover the pencil line or touch the spots initially?


  To ensure that the pigments do not dissolve before the chromatography process begins.
• What happens as the solvent rises up the chromatography paper?


  The solvent dissolves the pigments in the spots, causing them to move.
• What is the result of the pigments moving as the solvent continues to rise?


  Coloured mixtures will start to separate into spots or ovals positioned vertically above where they started.
• What is the purpose of the solvent in paper chromatography?


  The solvent dissolves the pigments in the spots and helps them to move up the paper.
• How does the movement of pigments indicate the separation of colored mixtures?


  As the pigments dissolve and move, they separate into distinct spots or ovals on the paper.
• What is a solvent?


  A liquid that will dissolve substances.
• What is the stationary phase?


  The paper - because it does not move.
• What is the mobile phase?


  The solvent - because the solvents move.
• Why does paper chromatography work?


  It works because different substances have different solubilities.
• Which substance is more attracted to the mobile phase? More soluble, or less soluble


  More soluble.
• Which substance travels further? More soluble, or less soluble.


  More soluble.
• Why do we draw our starting line in pencil?

  If we drew the line in pen, the pen ink could dissolve in the solvent and move up the paper.
• In which order did protons, neutrons and electrons become discovered?


  1. Electrons
  2. Protons
  3. Neutrons
• What is the plum pudding model? 


  An atom is a ball of positive charge with negative electrons embedded in it.

  
• What experiment was carried out to test the 'Plum Pudding Model'? 


  Alpha scattering Experiment.
• Why did they use gold in the alpha scattering experiment? 


  As it can be hammered into very thin foil (a few atoms thick).
• What charge do alpha particles have?


  A positive charge.
• How is the Alpha scattering experiment carried out? 


  • Scientists took a piece of gold foil
  • And then fired tiny particles at the gold foil. These were alpha particles.