Suck a bit of water into the syringe. This will create a partial vacuum inside the syringe, and with some luck you should be able to see the water in it boiling. In this picture, the line between the solid and liquid phases is the graph of the freezing point, and the line between the liquid and vapor phases is the graph of the boiling point. Between the solid and vapor phases is the graph of the sublimation point, like I was describing before. This graph is a general one, and the exact location of each line is different for every compound.
Water is one well-known exception, where the freezing point actually goes up as pressure decreases.