13. A sample of a pure white substance in powdered form is added to a beaker of pure water. After the mixture is stirred for 5 minutes, a very small amount of the white substance is seen at the bottom of the beaker. Which of the following most likely explains the observation?
Answer: B
The solution is saturated.
The observation that a very small amount of the white substance remains at the bottom of the beaker after stirring suggests that the solution has reached its saturation point, meaning no more of the substance can dissolve in the water.
A) Some of the water evaporated after adding the powder.
This option is incorrect because the problem does not indicate any evaporation of water. The presence of undissolved powder at the bottom is more indicative of saturation rather than a decrease in water volume.
B) The solution is saturated.
This option is correct as it directly explains why some of the white substance remains undissolved. When a solution reaches saturation, it can no longer dissolve additional solute, which aligns with the observation made after stirring.
C) The substance is not soluble in water.
While this could explain the undissolved powder, the context implies that some amount of the substance was initially dissolved before reaching saturation. Therefore, this option does not fully account for the situation presented.
D) A chemical reaction occurred.
This option is incorrect because a chemical reaction would typically result in the formation of new substances or changes in the properties of the original substances. The presence of undissolved powder does not indicate a reaction but rather a physical limit to solubility.
Conclusion
The correct explanation for the observation is that the solution is saturated, as evidenced by the undissolved powder at the bottom of the beaker. Other options either misinterpret the physical process involved or introduce elements (like evaporation or chemical reactions) that do not apply to the given scenario.