1.2.5 Observations & Measurements

• Scientists always record instructions for their experiments so that they can be repeated
• The instructions should allow an individual to successfully carry out the experiment without any additional help or input
• It is very important to record all required details within these instructions
• For example:
  • The aims of the investigation
  • The variables investigated
  • The apparatus used
  • The step-by-step method

• Often students struggle to think about the theoretical implications and explanations of the practical at the same time
• It is important to focus on these before and after the practical has been carried out to develop a solid understanding of the purpose of the experiment

• Making observations and recording measurements is a key skill in practical physics

Making Observations

• Observations should be recorded using the appropriate scientific vocabulary and should be precise
• Vague and ambiguous language, such as ‘the time wasn’t measured very accurately’, should be avoided
  • Instead, a more appropriate thing to say would be ‘using a stopwatch to measure the oscillation time of the pendulum introduced an error due to the reaction time of the experimenter’

Recording Measurements

• Making measurements using a range of equipment is essential in physics
• When using a digital measuring device eg. top pan balance or ammeter
  • Record all the digits shown
  • Except in the case of a digital timer, such as a stopwatch, there is no need to record to more than two decimal places

• When using a non-digital device eg. a ruler or a measurement cylinder)
  • Record all the figures that are known
  • Where appropriate, an additional estimated figure may be allowed

• Observations and measurements should be routinely recorded in a notebook, file or electronically
  • This enables a physical copy of the completed experiments to be kept

• These records should be made during the laboratory session and are the primary evidence of the outcomes of experiments
• The following will need to be included:
  • A clear explanation of the measurements or observations taken
  • Analysis of the raw data through graphs or calculations
  • The conclusions drawn from the outcomes of the experiment
  • An evaluation of the experiment eg. calculating errors and/or commenting on the limitations of experimental procedures

• The method does not necessarily need to be included unless an investigative approach is taken where the student develops part of the procedure themselves