What does osmolality measure in a solution?

Osmolality measures the concentration of solute particles in a solution. It specifically quantifies the number of osmotic particles, which can include ions, molecules, or other entities that contribute to the solution's osmotic pressure. This measurement is crucial for understanding the balance of fluids and electrolytes in the body, as it reflects the status of hydration and can influence how fluids move between various compartments in the body.

While the other answers relate to different properties of a solution, they do not capture the essence of osmolality. The mass of the solution pertains to its weight rather than its particle concentration. Temperature is a measure of thermal energy and does not provide information about solute concentration. Lastly, color indicates the presence of certain substances but does not relate to the fundamental concept of osmolality, which is strictly concerned with the number of particles in solution. Therefore, the correct choice focuses on the particles that define the osmolality of a solution.