Now, four major colligator properties are known vapor pressure, osmotic pressure, boiling point elevation, and melting point depression. I'm going to briefly talk about the first collage of property, vapor pressure. If you want to go into more detail about vapor pressure, check out my link below. So vapor pressure is simply the pressure due to the gas molecules found in dynamic equilibrium with their liquid molecules. Now, we see that adding non volatile solute decreases vapor pressure according to Rolls Law. Now, if you want to learn more about Rolls Law, check out my link below.