What two things can cause a shift in the phase of matter?
temperature and pressure
Temperature and pressure cause a shift in the phase of matter. The diagram following this explanation visually reinforces this.
If you hold pressure constant and increase temperature, you can move through all three phases of matter for water (ice
You can also boil water at room temperature by dropping the pressure. Note that if you were to touch the container or water, it will not be hot. This is the case for boiling water at higher elevations than those near sea level (think Denver vs. New Orleans).
This diagram essentially explains how pressure and temperature and their roles on phase changes.