What is the triple point?

In the phase diagram there is a triple point where the substance exists simultaneously as a solid, liquid and gas. Based on atmospheric pressure and temperature, three times the points have very specific values ​​and exist in balance. Although they have relatively few practical applications, triple points give scientists information about the behavior of the substance and are used to accurately calibrate thermometers. These diagrams look similar to the graph, with the temperature listed along the X axis and usually the pressure listed along the Y axis. For the Unars or simple single -component substances such as water, the lines form a y -shaped diagram. Each of the three lines y will indicate one condition and where three connections are a triple point.

The substance can easily exist in one state or even two of the temperature range. For example, water below 32 ° F (0 and DEGC;) exists as ice, solid. Heat the ice over its freezing point and begins to melt, existing as solid and liquid. On the contrary, water above 32 ° F (0 and DEGC;) is in liquid state. Heat it and a coupleAnd it will relax, allowing it to exist as gas and liquid.

Although existing in one or two states may occur in the range of temperatures existing in all three countries at the same time requires very restrictive conditions and therefore only seen in specific circumstances. For example, a triple water point occurs at 32.018 ° F (0.01 ° C) and a pressure of 0.006 atmosphere (ATM). Because triple points are thus limiting, they are usually seen only in closed systems.

However,

Triple Point Water has a practical application outside the closed system. It is his triple point that allows skaters to move over the ice. The body weight of the skater on a single blade of its skates increases the temperature of the ice only enough, while only exerting sufficient pressure to reach the triple point of water and allow skaters to move across the surface of the liquid while the steam is released.

Another practical applicationThe thermometers are in calibration. By using a cell that can contain water or liquid nitrogen and maintain a constant temperature on this cell for a fixed period of time, the scientist can determine the exact temperature reading necessary for the exact thermometer. Although there are many methods of thermometer calibration, calibration by triple points is usually considered to be the most accurate.