Defining the Variables

Bath Bomb Project

The Independent Variable

First, you will need to choose something to investigate (the independent variable). Some suggestions include:

  • Surface area of the bath bomb
  • Different amounts of citric acid or sodium bicarbonate
  • Different amounts of cornstarch
  • Different amounts of a fragrance
  • Different temperatures of bath water
  • Substituting citric acid for lemon juice or cream of tartar

The Control Variables

Don’t forget to keep all the other variables listed above constant (the control variables) to ensure a fair experiment!

The Dependent Variable

You’ll also need to pick something to measure (the dependent variable):

  • Amount of fizz
  • Length of time the bath bomb lasts
  • How nice it smells