Final answer:
A soluble non-volatile impurity, like table salt, increases the boiling point of a solution. An insoluble substance, like sand, does not significantly affect the boiling point of a solution.
Step-by-step explanation:
The presence of a soluble non-volatile impurity, such as table salt, will result in an increase in the boiling point of a solution. This is because the solute particles (ions) form attractions with the solvent particles (water molecules), preventing the water molecules from entering the gas phase and boiling. Therefore, the saltwater solution will have a higher boiling point than pure water.
On the other hand, an insoluble foreign substance, such as sand, will not have a significant effect on the boiling point of the solution. The sand particles do not dissolve or interact with the solvent molecules, so they do not affect the vapor pressure and boiling behavior of the solution.