What happens to boiling point (BP) and freezing point (FP) as the number of solute particles increases?

As the number of solute particles increases in a solution, the boiling point (BP) actually increases, while the freezing point (FP) decreases. This phenomenon is attributed to colligative properties, which are properties that depend on the number of solute particles in a solvent rather than the identity of the solute.

When a solute is added to a solvent, it disrupts the solvent's ability to form a solid (ice) at its normal freezing point, effectively lowering the freezing point of the solution. This is known as freezing point depression. In contrast, the presence of solute particles elevates the boiling point of the solution compared to the pure solvent; this is referred to as boiling point elevation. Essentially, the solute particles interfere with the solvent's ability to vaporize, thus requiring a higher temperature to reach the boiling point.

This is why the correct understanding highlights that as the number of solute particles increases, the boiling point increases and the freezing point decreases.