Stirring affects the rate of dissolving because it spreads the solvent's molecules around the solute and increases the chance of them coming into contact with it. Because of this, stirring makes solvents dissolve faster. Other factors affecting a solvent's solubility include temperature and particle size.
When performing a solubility experiment, using a stirring stick to move the solvent around the solute causes fresh portions of the solvent to come into contact with the liquid, which in turn makes it dissolve faster. There are other factors that affect a solvent's solubility as well:
Liquids act on the solvent's surfaceThe smaller the surface area is, the easier it is to dissolve. Therefore, grinding a substance down into smaller particles makes it easier to dissolve.
Heating the solution causes the solvent to dissolve fasterHowever, gasses become less soluble when the temperature increases. If a solvent is endothermic, it dissolves even faster under the pressure of temperature.
Applying pressure to a gas makes it more solubleHowever, it does not have much of an impact on liquids or solids.
The nature of forces between molecules influences solubilityIn order for the solvent to dissolve, the solute must be capable of breaking its hydrogen bonds, or its dispersion forces if the solvent is nonpolar.