chemistry paper 1 practicals

• Practical - Separation: Paper Chromatography

  separates substances in a mixture, dyes in ink -

  
  

  1. draw insoluble pencil line at bottom of filter paper sheet

  2. add spot of ink to line and place in solvent water

  3. solvent depends on mixture, some compounds dissolve well in water, others need ethanol

  4. make sure ink isn't touching solvent (so not dissolved)

  5. lid on container to stop solvent evaporating

  6. solvent seeps up paper, carrying ink

  7. each different dye moves at different rates so dyes separate. each dye forms a single spot

  8. any insoluble, in solvent, dyes stay at baseline

  9. when solvent has nearly topped out, take paper out beaker and dry

  10. end result is pattern of spots - chromatogram
• Practical - Separation: Filtration

  separates insoluble solids from liquids -

  
  

  1.filter paper folded in cone in funnel, solid left in filter paper, liquid in beaker. use with insoluble solid to be separated from liquid reaction mixture

  2. can be used in purification as well, solid impurities in reaction mixture can be separated using filtration
• Practical - Separation: Evaporation


  separates soluble solids in solutions -

  
  

  1. pour solution into evaporating dish

  2. slowly heat solution, solvent evaporates and solution becomes more concentrated. crystals start to form

  3. keep heating evaporating dish until only dry crystals are left

  
  

  quick, but only use if soluble salt doesn't decompose when heated
• Practical - Separation: Crystallisation


  separates soluble solids in solutions, even if solid decomposes when heated -

  
  

  1. pour solution into evaporating dish, gently heat. some solvent evaporates and solution gets concentrated

  2. once some solvent evaporates or when crystals start forming (point of crystallisation), remove dish from heat and allow to cool

  3. salt forms crystals as it's insoluble in cold, highly concentrated solution

  4. filter crystals from solution, leave in warm place to pat dry. or use drying oven/desiccator
• Practical - Separation: Separating Rock Salt


  rock salt: mixture of salt and sand. both compounds, salt dissolves in water and sand doesn't, difference in physical properties allows separation -

  
  

  1. grind mixture to make small, dissolvable salt crystals

  2. stir mixture into water, only the salt dissolves

  3. filter mixture, grains of sand left in filter paper, too big, salt passes through in solution

  4. evaporate water from salt to form dry crystals
• Practical - Separation: Simple Distillation

  separates liquid from solution -

  
  

  1. heat solution . lowest boiling point evaporates first

  2. vapour cools and condenses and is collected

  3. rest of solution stays in flask

  4. separates pure water from seawater, water evaporates, condenses and is collected as salt is left in flask

  5. only separates substances with very different boiling points, temperature above highest point mixes solutions again - use fractional distillation

  
• Practical - Energy Transferred in Reaction

  1. measuring energy released by chemical reaction in solution by taking reagent temp. mix in polystyrene cup and measure temperature at end

  2. energy is lost to surroundings, affecting readings so reduce with polystyrene cup in beaker of cotton wool for more insulation, lid for less evaporation energy loss

  3. works for neutralisation, or reactions between metals and acids/carbonates

  4. can investigate different variables on energy transferred like mass and concentration of reactants used
• Titration practical


  1. Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask

  2. Add a few drops of indicator and put the conical flask on a white tile

  3. Fill the burette with acid and note the starting volume

  4. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix

  5. Stop adding the acid when the end-point is reached (when the indicator first permanently changes colour). Note the final volume reading
• Repeat steps 1 to 5 until you get concordant titres
• More accurate results are obtained if acid is added drop by drop near to the end-point