Hi Kristi and Michaela,
This sounds like a great project to pursue. However, I am unsure whether photographs would be able to capture the relative changes in microbes produced by the different methods of hand-washing. An alternative way of collecting data would be to use agar plates.
You can read more about how agar plates may be used on this page: http://www.sciencebuddies.org/mentoring ... ?from=Home
Though the above link is addressing a different experiment, the agar plate and colony-counting methods for assessing bacterial content can be used for your project, too!
You are correct about the *dependent variable* being the amount of germs left on the hands after washing.
Your proposed experiment has multiple *independent variables*: (1) duration of hand-washing; (2) water temperature; (3) use of soap.
Since you have three independent variables, your experiment will require eight trials:
15 sec, cold, with soap
30 sec, cold, with soap
15 sec, cold, without soap
30 sec, cold, without soap
15 sec, warm, with soap
30 sec, warm, with soap
15 sec, warm, without soap
30 sec, warm, without soap
This will require careful use of controls. You will want to make sure you keep the following the same (controlled) for all eight trials: (1) person who is doing the hand-washing; (2) method of "dirtying up" the hands before washing; (3) method of hand-washing (washing between the fingers, the backs of the hands, or just the palms, etc.); (4) new, clean towel for drying hands.
Hope this helps! Let us know if you have further questions.