Question 4: Give 3 test tubes, each containing 5ml of distilled water, numbered (1), (2), (3). – Using identical spoons each scoop one of the following powdered solids: urea (protein fertilizer), sugar, and powdered chalk into the respective test tubes and mix well. – In tube (1), on the 5th spoon, urea could not dissolve any more, we saw solid powder deposited at the bottom of the test tube. – The same phenomenon in tube (2) occurs when the sugar reaches the 10th spoon; In tube (3), from the first spoon of chalk powder did not dissolve completely. Which of the following substances is the least soluble in water?
In tube (3), the first spoonful of chalk powder did not dissolve => The water solubility of chalk powder was the worst.
The answer to choose is: A