Atmospheric pressure decreases as altitude increases. in other words, there is more air pushing down on you at sea level, and there is less air pressure pushing down on you when you are on a mountain. if pentane (c5h12), hexane (c6h14), and hexanol (c6h13oh) are heated evenly at different altitudes, rank them according to the order in which you would expect them to begin boiling. 1 = boils first ; 4 = boils last hexane at sea level pentane at high altitude hexanol at sea level hexane at high altitude

At sea level, the size amid the 2 alkanes lets for pentane to simmer at a lower temperature than hexane. Phenol has a higher boiling point due to hydrogen bonding High altitude would have the same order while low pressure only cuts the temperature at which a solvent boils. Boiling has to do with molecular size, the occurrence/nonappearance of hydrogen bonds, and other steric issues.
So the answer would be pentane high altitude, hexane high altitude, hexane sea level, hexanol sea level. In order of boil first to boil last. This is clarified because altitude has a better effect on vapor pressure (and hence boiling points) than inter-molecular forces.