I believe the term is "catalyst," though I'm not sure. I seem to remember that "enzyme" means the same thing in biological terms.
A factor in a scientific experiment that is subject to change is called a variable.
The variable that is intentionally changed in an experiment is called the independent variable.
The factors which you change (vary) are called variables.
Variables
The part of an experiment that you test or manipulate change is called your independent variable.
A variable that doesn't change in an experiment is called a constant. Constants are used to ensure that only one variable is being tested for its effect on the outcome of the experiment.
In an experiment, factors that you change are called independent variables.
An experiment is almost always designed so that two (and no more) things will change.-- You, the experimenter, will change one of them as you desire.-- That will cause a change in the other one, which you will carefully measure.
A variable.
variables
changable factors
The variable that stays the same throughout the entire experiment is called the control.