Final answer:
When all of the sugar does not dissolve in a solution, it is likely because the sugar was too coarse and didn't mix well.
Step-by-step explanation:
When all of the sugar does not dissolve in a solution, it is likely because the sugar was too coarse and didn't mix well. The size of the sugar particles affects their ability to dissolve in the solvent. If the sugar particles are too big, they may not come into contact with enough solvent molecules to dissolve completely.