Why must measurements be taken while the temperature is cooling?

Taking measurements while the temperature is cooling is essential for accurately defining solubility limits. As a solution cools, the solubility of many substances decreases, meaning that the amount of solute that can dissolve in the solvent is lower at lower temperatures. By measuring solubility at various temperatures during the cooling process, one can establish a clearer relationship between temperature and solubility, allowing for the determination of the solubility limit at a specific temperature.

Furthermore, capturing data during this cooling period ensures that any changes in solubility can be documented as the solution transitions through different temperature states. This is crucial for applications in crystallization, where understanding the points at which solutes precipitate out of a solution is necessary for controlling product formation and purity.