What is the difference between triple point and critical point

Phase diagrams are charts which convey information of different states of a material; Solid, Liquid, Gas and presence of equilibrium or non-equilibrium conditions between them at different Temperatures, Pressures and Volume.

Critical point and triple point can be located on a phase diagram. Phase diagrams having variables other than the common variables of temperature, pressure and volume such as enthalpy, entropy etc are also used in industries to understand or design feasible systems for turbines, compressors, air conditioners etc.

Each substance has a unique phase diagram. The above phase diagram is called a pressure-temperature phase diagram because the chart uses pressure and temperature as its variables.

The lines on the diagram represent the conditions of temperature and pressure where at least two phases of the substance co-exist in equilibrium with each other. At least two phases means it can be solid or liquid, liquid or gas, gas or solid, or all the three phases together.

The line which is clubbed between the liquid phase and the gas phase is called the vaporization curve. The line which is clubbed between the solid phase and the liquid phase is called melting curve. The line which is clubbed between the solid phase and the gas phase is called sublimation curve.

The critical point and triple point are labelled on the diagram. Both points act as end points of the vaporisation curve. If any substance is in a vapour-liquid equilibrium then it means the two phases; Vapour and Liquid are co-existing simultaneously. On the phase diagram it will be indicated by any point on the vaporisation curve except the end points. If we increase the temperature of such a substance which is in vapour-liquid equilibrium then the pressure will increase in such a way that the state of the material will move on the vaporization curve in the direction of increasing temperature or increasing pressure.

If we keep on increasing the temperature, nature will keep on increasing the pressure to maintain the state of the vapour-liquid equilibrium. Increasing temperature does mean that the quantity of the gas may increase and the quantity of the liquid may decrease if the system is brought from one state to another but the overall quantity remains constant and the system remains in equilibrium. No separation between them can be seen. The temperature at this point is called critical temperature and the pressure is called critical pressure.

Triple point of a substance is the temperature and pressure at which the three phases gas, liquid, and solid of that substance coexist in thermodynamic equilibrium. The point at which saturated liquid and saturated vapour lines meet is called the critical point The point at which fusion line and sublimation line and vapourisation meet is called the triple point It is represented by a point on p-v-T surface It is represented by a point on p-T diagram but appears as a line on p-v-T surface At critical point there is no distinction between the liquid and vapour phases.

Viva Differences. Critical Point In thermodynamic, the critical point also referred to as critical state is a point on a phase diagram at which both the liquid and gas phases of a substance have the same density and therefore indistinguishable. Triple Point Phase Diagram Triple point of a substance is the temperature and pressure at which the three phases liquid, gas and solid of that substance coexist in thermodynamic equilibrium. The line that separates solid and liquids bends right.

If the solid phase is less dense than the liquid phase, the line that separates solid and liquids bends left. Look at the lines on the phase diagram. If you go to a line and then increase pressure you move to a new phase, the denser phase. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Physics What is the difference between the critical point and the triple point?

Ben Davis June 7, What is the difference between the critical point and the triple point? Why is there a triple point? Why is the triple point important? What is the triple point of co2? Does the triple point of water occur in nature? What happens at the triple point of water answers?