Step 1 :The question is asking about the change in entropy for different systems under different conditions. Entropy is a measure of the disorder or randomness of a system. Generally, processes that increase the disorder of a system will increase the entropy.
Step 2 :For the first system, dissolving potassium chloride in water will increase the disorder of the system as the ions become dispersed in the water.
Step 3 :For the second system, mixing two gases will also increase the disorder of the system as the gas molecules become more randomly distributed.
Step 4 :For the third system, adding water to a solution will also increase the disorder of the system as the water molecules become dispersed in the solution.
Step 5 :Therefore, for all three systems, the change in entropy ($\Delta S$) should be greater than 0.
Step 6 :This is a qualitative analysis based on the principles of thermodynamics and does not require a Python code for calculation.
Step 7 :Final Answer: For all three systems, the change in entropy ($\Delta S$) is greater than 0, i.e., $\boxed{\Delta S > 0}$.