The nature of the solute
Temperature is one factor. Hold it still, and something about the solute itself turns out to be another.
Activity 3.1.8 — method
Take 50 ml of water into each of two small beakers, both at the same temperature. Weigh out 50 g each of sugar and of salt. Add salt a little at a time to one beaker and sugar a little at a time to the other, dissolving as you go. When no more will dissolve, stop and weigh what is left in each case. Are the two amounts the same?
The observation
They are not. Different solutes dissolve in unequal amounts in equal volumes of the same solvent at the same temperature.
What this activity holds still
The design is what makes the conclusion safe. Three things are deliberately the same in both beakers:
- The solvent — water in both
- The volume — 50 ml in both
- The temperature — the same in both
Only the solute differs. So the difference in how much dissolved can only be down to the solute.
The nature of the solute affects solubility.