How can boiling points be changed?
By changing the pressure or adding solutes.
An increase in pressure will cause an increase in the boiling point. The vapor pressure created by gas particles hitting the container walls will be opposed by the atmospheric pressure above the liquid. If the atmospheric pressure is increased, the vapor pressure required to overcome the atmospheric pressure is greater.
Adding a solute blocks the solvent at the surface of the liquid. This makes it harder for the solvent molecules to reach the vapor pressure necessary to become a gas. The higher the solute concentration, the lower the maximum vapor pressure (at that temperature) becomes, and the harder boiling is.
Increasing either the atmospheric pressure or the solute concentrations will increase the boiling point. Decreasing the atmospheric pressure or the solute concentrations will decrease the boiling point.