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?
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.
You are correct that there are two variables in this experiment. The independent variable is the water temperature, as this is the variable that is manipulated by the scientist. The dependent variable is the solubility of calcium carbonate, as it changes in response to the independent variable.
Regarding the speed of stirring, while it does have an effect on the time it takes for the water to become a saturated solution with calcium carbonate, it does not directly affect the solubility. The solubility of calcium carbonate is a constant value, regardless of the speed of stirring, if given enough time to reach equilibrium.
In this experiment, the speed of stirring can be considered a controlled variable. Controlled variables are the factors that are kept constant throughout the experiment to ensure that they do not affect the outcome. In this case, the speed of stirring can be controlled by ensuring that it is the same for all trials.
Therefore, the two variables in this experiment are the water temperature (independent variable) and the solubility of calcium carbonate (dependent variable). Additionally, there are several controlled variables, including the speed of stirring.