Here's why:

* Vapor Pressure: The boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding atmospheric pressure. When you add a solute, it disrupts the solvent molecules' ability to escape into the vapor phase. This is because the solute molecules occupy some of the surface area and interfere with the solvent molecules' movement.

* Lower Vapor Pressure: As a result, the vapor pressure of the solution is lower than that of the pure solvent at any given temperature.

* Higher Boiling Point: To reach the same vapor pressure as the pure solvent and boil, the solution needs to be heated to a higher temperature.

Key Factors:

* Nature of the Solute: The effect of the solute on the boiling point depends on its nature. Non-volatile solutes (those that don't readily evaporate) have a greater impact than volatile solutes.

* Concentration: The higher the concentration of the solute, the greater the boiling point elevation.

Example:

Adding salt to water raises the boiling point of the water. This is why adding salt to your pasta water helps it cook faster. The higher boiling point allows the water to reach a higher temperature, speeding up the cooking process.

Formula:

The boiling point elevation can be calculated using the following formula:

ΔTb = Kb * m

where:

* ΔTb = boiling point elevation

* Kb = molal boiling point elevation constant (a property of the solvent)

* m = molality of the solution (moles of solute per kilogram of solvent)