How does adding salt change water's boil point?

Adding salt (a solute) to water (a solvent) raises the boiling point. This phenomenon is known as boiling point elevation, which is a colligative property. This means the effect depends on the number of dissolved particles, not their type. The salt ions (Na+ and Cl-) in the water get in the way of the water molecules, making it more difficult for them to escape into the gas phase. 

Because of this interference, more energy (a higher temperature) is required to make the water boil. It is important to note that for the amount of salt typically used in cooking (e.g., for pasta), the increase in the boiling point is very small, often less than one degree.