If you can fruits and vegetables, or are an ardent tea drinker you will have had some experience with this. A tea kettle has a closed lid which raises the pressure inside the kettle as the water begins to boil. This causes the boiling point of the water to rise noticably which allows you to pour a very hot cup of tea at an altitude where this is not normally possible. This is also why many of us burn our lips on coffee and tea when we go to Portland or the coast. Atmospheric pressure is noticably higher and it leads to hotter hot drinks.
Pressure cookers work on the same principle.
The point I am trying to make is that neither the melting point or the boiling point are constants and depend quite strongly on the specific circumstances of the experiment. In our particular case we are going to be most concerned with the behavior of fluids and gasses and the characteristics of the transition between these two states. You are likely to have heard of the Ideal Gas Law at some point in your life and it contains a host of important conceptual information. From our point of view what is critically important is that you have an solid understanding of what is means conceptually and the heck with the numbers. In that little equation are condensed years of your life experience.