Nope, it's a physical change. When ice melts it changes into liquid water, it's still water. Changes in which no new substances are formed are physical changes, hence this is a physical change.
Stir the water continuously, this is the only logical answer. Adding powdered sugar, decreasing the volume, increasing the amount of suga, cooling, all don't make the sugar dissolve quicker.
The answer is Boyle's law. Boyle's law states that the volume of a fixed mass of a gas is inversely proportional to its pressure at a constant absolute temperature.
That is; V α 1/P , at constant temperature and a fixed amount of the gas.
Such that V= k/P where k is a constant
Crush the limestone... it would give more area for the acid to react