When you add sugar to a cold drink, you may stir it to help the sugar dissolve. If you don’t stir, the sugar may eventually dissolve, but it will take much longer. Stirring is one of several factors that affect how fast a solute dissolves in a solvent. Temperature is another factor. A solid solute dissolves faster at a higher temperature. For example, sugar dissolves faster in hot tea than in ice tea. A third factor that affects the rate of dissolving is the surface area of the solute. For example, if you put granulated sugar in a glass of ice tea, it will dissolve more quickly than the same amount of sugar in a cube. That’s because granulated sugar has much more surface area than a cube of sugar. You can see videos of all three factors at these URLs
Context:
Justin and Alejandro are conducting a chemical experiment involving sodium hydroxide. A key part of the reaction is ensuring that the sodium hydroxide is dissolved in water before adding the other materials. Justin adds the sodium hydroxide to reaction A, and begins stirring the mixture with a spoon. Alejandro also adds sodium hydroxide to his reaction, reaction B, but doesn't stir it because he is lazy.
Q: Whose sodium hydroxide, Justin's or Alejandro's, will dissolve faster?