What is a phase diagram?

The

phase diagram is a graph that is commonly used in sciences, especially chemistry, to visualize the conditions under which substances exist at a given stage and change in a different stage. The phase addressed by the phase diagram are usually a solid, liquid and gaseous phase. The schemes are set as graphs with pressure on the vertical axis and temperature on the horizontal axis. The diagram curves are points in which different phases are in the state of balance and open spaces represent different phases. A large amount of valuable information, such as boiling point and freezing of the substance at a given pressure, can be collected from such a diagram. Above the curve is a solid phase and below it is a gas phase. The curve itself represents a balance between solid and gas; Under very low pressure conditions, there is rarely liquid. This balance is also referred to as the sublimation point . Finally, at a specific temperature and pressure, the curve branches into two different curves and the space between them represents a liquid phase.

The

point at which the curve branches into two curves is referred to as the triple point . This is important because it represents specific temperature and pressure conditions in which the solid, liquid and gaseous phases are in the state of balance. This means that the substance presented by the graph is constantly changing between the phases-all three are present at the moment.

At a certain temperature and pressure, the lower curve ends at a point referred to as a critical point . This usually occurs at relatively high pressure and temperature. Under pressure and temperature conditions higher than a Critical point, there is no recognizable resolution between the liquid phase and the gaseous phase.

Phase diagrams

are useful and can be very important for chemists. For example, a curve on a phase diagram dividing liquid and gas is the conditions under which they will both be in balance. In other words, the curve represents the boiling point of the substance.