Phase behavior for water is represented on a log pressure versus temperature diagram. Use the first drop-down menu to select for either an isothermal or isobaric process. Select the particular phase transition (sublimation, melting, vaporization, triple point) from the second drop-down menu. For isobaric transitions, you can add heat with the slider. For isothermal transitions, the specific volume is changed. The relative amounts of each phase present are shown in the bar graph. A log pressure-temperature graph with an expanded temperature scale is inserted for isothermal melting because of the steepness of the phase transition line. At the triple point, the three phases are present simultaneously. Select “display Gibbs phase rule” to show the phase rule applied at the location of the black dot.