Which factor would most likely affect the solubility of a substance?

The solubility of a substance is primarily influenced by the type of solvent used. Different solvents have varying chemical properties, such as polarity, which affects the interactions between the solute and solvent molecules. For example, polar solvents like water are more effective at dissolving polar solutes due to the attraction between the charged regions of the molecules. Conversely, nonpolar solvents will better dissolve nonpolar solutes. This principle is often summarized by the phrase "like dissolves like," indicating that solutes will dissolve best in solvents with similar chemical properties. Therefore, selecting an appropriate solvent is crucial in determining how well a substance will dissolve.

The other choices do not have a significant impact on the fundamental solubility of a substance. The color of the solute is a physical property that does not affect how it interacts with the solvent. The shape of the solute particles may influence the rate of dissolving but does not inherently change their ability to dissolve. Additionally, the size of the container has no effect on solubility itself; it simply determines the volume of solution. Thus, the type of solvent is the critical factor affecting solubility.