You're absolutely right! Adding a solute to a pure liquid generally increases its boiling point and decreases its freezing point. This is due to a phenomenon called colligative properties.

Here's a breakdown of why this happens:

Boiling Point Elevation:

* Vapor Pressure Lowering: When you add a solute to a solvent, the solute particles interfere with the solvent molecules at the surface. This makes it harder for the solvent molecules to escape into the vapor phase, leading to a lower vapor pressure.

* Higher Boiling Point: For a liquid to boil, its vapor pressure must equal the atmospheric pressure. Since the vapor pressure is lowered by the presence of the solute, the liquid needs to reach a higher temperature to achieve this balance. Therefore, the boiling point is elevated.

Freezing Point Depression:

* Disruption of Crystal Lattice: When a liquid freezes, its molecules form a regular, ordered crystal lattice. The solute particles disrupt this orderly arrangement, making it more difficult for the solvent molecules to form a stable crystal.

* Lower Freezing Point: Because the solute interferes with the formation of the crystal lattice, the solvent molecules need to be cooled to a lower temperature to solidify. This results in a lower freezing point.

Key Points:

* Colligative Properties: These properties depend only on the concentration of solute particles in the solution, not on the specific type of solute.

* Non-Volatile Solutes: The explanations above primarily apply to non-volatile solutes (those that don't readily evaporate). If the solute is volatile, its own vapor pressure needs to be considered as well.

* Electrolytes: For solutes that dissociate into ions (electrolytes), the effect on boiling point elevation and freezing point depression is magnified because there are more particles in solution.

Let me know if you would like more details or examples!