Final answer:
Changing to a mainly cold water solvent helps isolate the product by exploiting differences in solubility, while an ice bath slows down molecular movement to encourage crystal formation.
Step-by-step explanation:
Changing the solvent from ethanol to mainly cold water helps to isolate the product by taking advantage of the difference in solubility between the product and impurities. By adding cold water, the solubility of the product decreases while the solubility of the impurities remains the same. This causes the product to crystallize out of solution, allowing for its separation.
The test tube was placed into an ice bath when performing the recrystallization to further decrease the solubility of the product and encourage the formation of larger, purer crystals. Lowering the temperature helps to slow down the molecular movement in the solution, increasing the likelihood of the product molecules coming together to form solid crystals.