Liquids, Solids, and Phase Transitions
A phase diagram illustrates the physical state of a substance with respect to the temperature and the pressure of the surroundings. The points plotted to draw the phase diagram are derived experimentally, and are usually plotted with temperature on the x-axis and pressure on the y-axis. A typical phase diagram is shown below in Figure-1.
The critical temperature of a substance is best defined as:
A The temperature below which a gas cannot be liquefied B The temperature above which a liquid cannot be vaporized C The temperature above which a substance exists only as gas D The temperature which is essential for a substance to obey ideal gas laws