Particle size vs dissolving rate of sucrose
I have found in Germany sugar crystals that are about 5 mm thick. If you are able to get some, you may drop one of these crystals in a beaker with 50 mL water and an stirring bar. If not take a standard sugar cube. Using a watch, measure how long it takes for the crystal to be dissolved. Now start again with another rotating speed. Now break a new crystal in two or three parts with a hammer. And start again with smaller crystals (to be weighed in advance). Repeat the measurements. Report these values on a graph vs rotating rate, or vs. weight of sugar, or vs. temperature. Now start again with powder, and even with the sugar powder used in bakery which is made of extremely fine grains. This is just ideas.