Here's why:

* Boiling Point Elevation: When a nonvolatile solute (one that doesn't easily evaporate) is added to a solvent (like water), it disrupts the vapor pressure of the solvent. The solute molecules interfere with the solvent molecules escaping into the gas phase.

* Higher Vapor Pressure Required: To reach the boiling point (where vapor pressure equals atmospheric pressure), the solution now needs a higher temperature. This is because the presence of the solute has lowered the vapor pressure of the solvent.

* 1 ATM: At a standard pressure of 1 atmosphere, pure water boils at 100 degrees Celsius. However, the solution will need to reach a temperature above 100 degrees Celsius to achieve the same vapor pressure and boil.

Let me know if you'd like more details on boiling point elevation!