Precipates and reactions

• Experimental skills required for Practical Test and Alternative to Practical

  • Same experimental skills to be developed and learned
  • Understanding of the same experimental contexts
  • Test the same assessment objective, AO3
• Experimental contexts candidates are expected to be familiar with

  • Simple quantitative experiments, including the measurement of volumes of gases or solutions/liquids, masses, temperatures, times, lengths, rates of reaction, salt preparation
  • Separation and purification techniques, including filtration, crystallisation, simple distillation, fractional distillation, chromatography, electrolysis
  • Identification of metal ions, non-metal ions and gases
  • Test-tube reactions of dilute acids, including ethanoic acid
  • Chemical tests for water
  • Tests for oxidising and reducing agents
  • Heating and cooling curves
  • Titrations
  • Solubility, melting points and boiling points
• What candidates may be required to do

  • Demonstrate knowledge of how to select and safely use techniques, apparatus and materials (including following a sequence of instructions where appropriate)
  • Identify apparatus from diagrams or descriptions
  • Draw, complete or label diagrams of apparatus
  • Use, or explain the use of, common techniques, apparatus and materials
  • Select the most appropriate apparatus or method for the task and justify the choice made
  • Describe tests (qualitative, gas tests, other tests)
  • Describe and explain hazards and identify safety precautions
  • Describe and explain techniques used to ensure the accuracy of observations and data
  • Plan experiments and investigations
  • Identify the independent variable and dependent variable
  • Describe how and explain why variables should be controlled
  • Suggest an appropriate number and range of values for the independent variable
  • Suggest the most appropriate apparatus or technique and justify the choice made
  • Describe experimental procedures
  • Identify risks and suggest safety precautions
  • Describe how to record the results of an experiment
  • Describe how to process the results of an experiment to form a conclusion or to evaluate a prediction
  • Make reasoned predictions of expected results
  • Make and record observations, measurements and estimates
  • Take readings from apparatus (analogue and digital) or from diagrams of apparatus
  • Take readings with appropriate precision, reading to the nearest half-scale division where required
  • Make observations, measurements or estimates that are in agreement with expected results or values
  • Take sufficient observations or measurements, including repeats where appropriate
  • Record qualitative observations from chemical tests and other tests
  • Record observations and measurements systematically, for example in a suitable table, to an appropriate degree of precision and using appropriate units
  • Interpret and evaluate experimental observations and data
  • Process data, including for use in further calculations or for graph plotting, using a calculator as appropriate
  • Present data graphically, including the use of best-fit lines where appropriate
• Apparatus and materials required for experiments

  • aluminium foil
  • balances to measure up to 500g, with precision of at least 0.1g
  • beakers or cups made of an insulating material such as polystyrene, approximate capacity 150 cm³
  • beakers, squat form with 3p, 1dm, 250am and 100cm
  • boiling tubes, approximately 150mm x 25mm
  • Bunsen burners
  • burettes, 50cm (150385 or grade B)
  • conical flasks, within the range 50cm to 250cm
  • delivery tubes
  • filter funnels and filter papers
  • flame test wires or alternative apparatus
  • measuring cylinders, 100cm 50cm, 25am, 10 am 0506706 or 1504788 or grade 8)
  • paper for labelling glassware
  • pipette fillers
  • racks for test tubes and boiling tubes
  • red and blue litmus paper
  • retort stands, bosses and camps
  • small droppers or teat pipettes
  • small funnels for filling burettes
  • spatulas
  • stirring rods
  • stirring thermometers, -10°C to +110°C, with 1°C graduations
  • stoppers for test-tubes and boiling tubes
  • stopwatches to measure to an accuracy of 1s
  • test-tube holders (to hold test-tubes or boiling tubes)
  • test-tubes (Pyrex or hard glass), approximately 125 mm x 16mm
  • tripods
  • universal indicator paper
  • volumetric pipettes, 25cm (150648 or grade 8)
  • wash bottles
  • white tiles
• Every effort is made to minimise the cost to and resources required by centres. Experiments will be designed around basic apparatus and materials which should be available in most school laboratories are easily obtainable.
• Hazard codes


  • C - corrosive
  • HH - health hazard
  • F - flammable
  • N - hazardous to the aquatic environment
  • MH - moderate hazard
  • T - acutely toxic
  • O - oxidising
• Appropriate safety equipment must be provided to students and should at least include eye protection
• Candidates are not expected to be familiar with the preparation of these reagents
• Identify


  1. dilute hydrochloric

  2. 10man

  3. 14

  4. [MH]]

  5. gou als

  6. 10md/end,

  7. small 30,

  8. +4
• Instructions


  1. 035-00 of decentrated p5-37%

  2. GIOR

  3. 64 of concentrated (70%) HD (C)

  4. om of concentrated (98%)

  5. Hake the pt 1 with led

  6. WITH

  7. 訂

  8. aquedut sodan

  9. 10mp/314 No

  10. Diese 400g of Nanof

  11. hydride

  12. Care the proons of solutionis esthe

  13. Serwater

  14. lodide

  15. 0027MD,

  16. [MM]

  17. addified agen

  18. potassium

  19. manganate(VI)

  20. methyl orange

  21. [MH]NT

  22. indicator

  23. (pH range 3.1-4.4

  24. screated matry

  25. screened methylaring

  26. 32-423

  27. thynolphthalein

  28. dm of slation

  29. Desolve £5 of AgNO, [C]

  30. sektion

  31. Propane tresh mewater by leaving dated w

  32. to sard over sold CalOH, [C] for

  33. a chuking occasionally Decant or Ster the

  34. Denial 166g of Kl in each dem al solution

  35. Cinave 1.3goo, HH||0||HH] [N

  36. Mix vs of 002melanco, and

  37. 10mel(R,50 MH

  38. Use commercially produced soon or

  39. 04gof said methyl orange

  40. [MH] IN][T] 200 on of 99% ethasa [F]]HH||

  41. [MH] and make up to 1am with dolled te

  42. Use commercially prodiced soluson or d

  43. 1g of adid methyl change indicator [C] H

  44. [MH] [NT]

  45. [MH] N10

  46. thymolphthalein indicator Use

  47. of xylene cyanel HH
• Tests for anions
• Test for carbon dade

  Effervescence, carbon diode produced
• Test result


  • White ppt
• Then add


  White ppt
• Potassium manganate (VI) changes


  Colour from purple to colourless
• Tests for aqueous cations
• Effect of aqueous ammonia


  White ppt, insoluble in excess
• Effect of aqueous ammonia

  No ppt, a very slight white ppt soluble in excess
• Effect of aqueous ammonia

  Light blue ppt
• Effect of aqueous ammonia

  Dark blue ppt, soluble in excess
• Effect of aqueous ammonia


  Red-brown ppt, soluble in excess
• Tests for gases
• Flame tests for metal ions
• Flame test result
• The reaction between silver nitrate (AgNO3) and sodium chloride (NaCl) produces a white, crystalline precipitate of silver chloride (AgCl).
• Precipitation is the formation of an insoluble solid from two or more soluble substances.
• A precipitate is formed when one substance reacts with another to form an insoluble compound