Why is it important to control all of the variables except one in an experiment?

Darla claims that the first periodic table developed by mendeleev was not completely accurate, so it is not useful at all. harmony argues that it establish the periodic table we use today, making it more credible. who is correct and why? darla is correct, because a model that has any mistakes should be thrown out. darla is correct, because a good model would not need to change. harmony is correct, because mendeleev’s model had all of the information correct in the first version. harmony is correct, because mendeleev’s model made predictions that came true.

What is the most common reason for matter changing its state?

What is the solubility-product constant of barium sulfate, baso4, if a saturated solution is 1.03 ´ 10-5 m?