Sources

http://www.chemistryexplained.com/Ce-Co/Colligative-Properties.html
http://www.scienceiscool.org/solutions/vplowering.html
http://www.sparknotes.com/chemistry/solutions/colligative/section1.rhtml
http://www.chem.arizona.edu/~salzmanr/480a/480ants/colprop/colprop.html

Examples of Vapor Pressure Lowering

When you place a glass of water in an open room, it will evaporate completely, however, if a cover is placed above the glass, the space above the liquid will gradually contain a constant amount of water vapor. Also, in some steam engines the cylinder can be cooled to lower the vapor pressure of the steam and create a suction on the back side of the piston to get extra power. By dissolving a solute in a liquid solvent, the vapor pressure of the liquid will come down. This happens because some liquid molecules will need to attach to the solute and therefore there are fewer liquid molecules to vaporize.

Property Change

The vapor pressure of a liquid is the equilibrium pressure of gas molecules from that liquid above the liquid itself. By adding a solute the vapor water pressure depression is the lowering of a solvent’s vapor pressure . Vapor pressure is a solvent’s ability to evaporate or boil off surface molecules. Sometimes, a solvent cannot evaporate easily, when a solute is added. This happens because the solute particles hinder the solvent’s natural behaviors by getting in the way of the solvent's molecules and their inter molecular forces.