Final answer:
At equilibrium in a solution, solute particles are surrounded by solvent particles and can either dissolve into the solution or adhere to the surface of undissolved solute particles in a process called crystallization.
Step-by-step explanation:
At equilibrium, solute particles are surrounded by particles of the solvent, carrying the solute from its original phase. Each solute particle can either dissolve into the solution or adhere to the surface of an undissolved solute particle in a process called crystallization. This creates a dynamic equilibrium between dissolution and crystallization.