Planning an investigation

Identify the variables

Independent variable – the variable that is altered during a scientific experiment.

Dependent variable – the variable being tested or measured during a scientific experiment.

Controlled variable – a variable that is kept the same during a scientific experiment. Any change in a controlled variable would invalidate the results.

Example

Practical B3 - Investigating the effect of temperature on the action of an enzyme

  • Independent variable – temperature.
  • Dependent variable – time taken for starch to be digested.
  • Controlled variables – pH, enzyme concentration and volume of enzyme.