Constant variables are those items in your experiment which you will not be changing. For example, the amount of water in each bottle.
Unfortunately, I've never heard of the term "relative variable", but perhaps this site will shed some light on your experiment: http://www.sciencebuddies.org/science-fair-projects/project_variables.shtml
Edit: I've been doing a bit of searching, and I can't find an explanation for "relative variables". =/
Years of doing labs in school.
· 1 decade ago