Today, Riya performs two set of experiments carefully to study the length of the foam formed are as follows: Set I: Riya takes 10 ml (mililitre) of distilled water in test tube “A” and adds 5-6 drops of liquid soap in it and shakes the test tube. Set II: Riya takes 10 ml of distilled water in a test tube “A” and adds 5-6 drops of liquid soap with half spoonful of Calcium sulfate (or calcium sulphate, CaSO4) in it and shakes vigorouisly the test tube. What do you think. Write your observation and reason.

Based on the provided information, it seems like Riya is conducting experiments to study the length of the foam formed under two different conditions.
Observations: Set I:
Riya takes 10 ml of distilled water in test tube “A.”
Adds 5-6 drops of liquid soap.
Shakes the test tube.
Observation: Foam is formed.
Reason: The addition of liquid soap to water creates a lather or foam due to the formation of soap molecules surrounding air pockets, stabilizing them and creating bubbles.

And, Set: II will form less foam because it consist of hard water due to the presence of CaSO4.