See the question from earlier regarding how many variables are in the experiment. I think speed of stirring is a variable. So, my answer would be 3 variables. One for water temp., speed of stirring, and the calcium carbonate solubility. Is this right?

Question

I don't think speed of stirring is a variable. True, it makes a difference in the time it takes for the water to become a saturated solution with CaCO3, but it doesn't affect the solubility. That may sound contradictory; however, the solubility of CaCO3 will be some number. IF YOU GIVE IT ENOUGH TIME, the same amount of CaCO3 will dissolve in the same amount of water but it may take longer for the solution to become saturated without stirring. If you are performing a rate of solution experiment then the speed of stirring is a variable. If you are performing a solubility test, we normall stir in order to reach equilibrium faster but .....I hope you see what I mean. As to solubility of CaCO3, won't that be the same value regardless of anything except T (assuming we give it time to reach equilibrium)?

There are three types of variables: independent, dependent, and controlled. There is only one independent variable in a good experiment, and it is the variable manipulated by the scientist. In this case, that would be water temperature. The dependent variable changes in response to the independent variable, and that is solubility here. I would stop there and say the answer is two, as there are so many controlled variables-everything from using the same amount of water to using the same container. I agree with DrBob, and I don't it is a variable because if you stir faster, you won't have to stir as long, but if you stir slower, you will have to stir longer.