Planning an experiment

Independent variable (1)

• The Independent variable is the one we change. e.g. we changed the temperature the enzymes were incubated at.

Dependent variable (1)

• The Dependent variable is the one we measure (this is the number you are writing down, and it usually has a unit, e.g. degrees Celsius, metres, etc)
• How to remember it: Dairy Milk Ice Cream (Dependent you measure, independent you change).

Control variables (3)

• Control variables: any other factor that can change the outcome of the experiment, e.g. volume or concentration of solutions (never say 'amount' ever, its useless). The temperature, pH, etc.
  • starting temperature of the water ; temperature of, environment / surroundings / room ; material the containers are made from ; total time ; sampling time / measure every minute ; concentration / pH, of acid; volume of acid; type of acid / named acid same type of indicator / named indicator
• A control is not a control variable. The control is the exact same experiment with the independent variable removed, to see if something happens anyway.
  • control and description of the control e.g. using boiled enzyme / water instead of enzyme ;
• Safety precaution (1)
  • goggles and gloves
• Procedure (3)
  • equilibration (both solutions in water before mixing)
  • take samples
  • use of buffer
  • use of colorimeter
  • what to measure and method of measurement
  • use of pH meter
  • enzymes - preparation of food samples; apparatus to measure food;
• Repeat investigation twice and compare results (1)

Graphs

• Use a pencil
• X axis (horizontal one) is the independent variable, and y (vertical) is the dependent variable. DRY MIX.
• Line of best fit can be a straight line or smooth curved line. Don't join the dots, just go for it. Ignore anomalous results.
• Label axis and INCLUDE UNITS
• Do not include a title.

Tables

• Draw with a ruler and pencil