On dissolving sugar in water at room temperature, solution feels cool to touch. Under which of the following cases dissolution of sugar will be most rapid?

Dissolution of sugar in water will be most rapid, when powdered sugar is dissolved in hot water because powdered form can easily insert in the vacancies of liquid particles. Further dissolution of sugar in water is an endothermic process (as cooling is Produced). Hence, high temperature will favour the dissolution of sugar in water.