• When recording results of experiment, both?quantitative?and?qualitative?data should be obtained
• Quantitative data?is obtained from measurements whereas?qualitative data?is non-numerical information that comes from observations
• Quantitative data?is always associated with random errors/uncertainties, determined by the apparatus, and by human limitations such as reaction time
• Where there are several items of data you should record your data in a table with appropriate?headings?and?units:

Data Table showing headings and units

• Uncertainties?are the same as?random errors
• Uncertainties?express the confidence to which the measurement can be taken
• Treatment of?uncertainties?depends on the type of instrument used

Using analogue instruments

• Any instruments that have an?analogue scale, the uncertainty is taken as?half the smallest division?on the scale
• For example,
  • A thermometer that reads to 1^oC, the uncertainty would be?+0.5?^o?C
  • A burette that reads to 0.10 mL, the uncertainty would be?+0.05 mL

Using digital instruments

• Any instruments that have a?digital?scale, the uncertainty is taken as the?smallest division?on the scale
• For example,
  • An electronic balance that reads to 0.01 g, the uncertainty would be?+0.01 g

Other uncertainties

• Other sources of uncertainty can arise where the judgement of the experimenter is needed to determine a changing property
• For example,
  • Judging the end point of a?titration?by looking at the colour of the?indicator
  • Controlling a stopwatch in a rate of reaction experiment
  • Deciding when to extinguish the flame in an?enthalpy of combustion?experiment
• These uncertainties are very difficult to quantify, but they should be commented on as a source of error in an?evaluation