Here's why:

* Temperature and Molecular Motion: Higher temperatures mean molecules move faster. In hot water, the water molecules have more energy and move more rapidly, increasing their ability to collide with sugar molecules and break them apart.

* Solubility: The solubility of sugar in water increases with temperature. This means that hot water can hold more dissolved sugar than cold water.

In addition to temperature:

* Stirring also helps dissolve sugar faster by bringing fresh water molecules into contact with the sugar crystals.

* Surface area matters. Crushed sugar dissolves faster than large sugar crystals because there's more surface area exposed to the water.