Question

A spoon of salt is added to water. Which of these will increase how fast the salt dissolves? Check all of the boxes that apply.

adding another spoon of salt

stirring the salt and water

cooling the water

crushing the salt so the grains are smaller

adding more water

Answer 1

[ ] adding another spoon of salt — No. That raises the amount of solute and the solution concentration, so it doesn't make the original spoon dissolve faster (it can even slow dissolution or cause saturation).

[x] stirring the salt and water — Yes. Stirring moves saturated solution away from the salt and brings fresh solvent to the surface, increasing the dissolution rate.

[ ] cooling the water — No. Cooler water slows molecular motion and diffusion, so salt dissolves more slowly.

[x] crushing the salt so the grains are smaller — Yes. Smaller grains have more surface area for the same mass, so they dissolve faster.

[x] adding more water — Yes. More water lowers the local concentration and increases the concentration gradient, so salt dissolves faster.

(Also: increasing temperature would speed dissolution; cooling does the opposite.)