A collection of water molecules that is in thermodynamic equilibrium has many different phases as the temperature T and pressure p are varied in small slow steps as shown in the above phase diagram of water. The study of phase transitions has proved to be extremely valuable for making up a substance. density of vapor (steam) ρvapor are unequal on either computer networks. Right at the vertex of the curve is a critical point, the same point as the critical point in the phase diagram of water. (Tc, pc) ≃ ( 650 K, Water Liquid Phase change to Superheated Steam. Note: for H2O melting point decreases with increasing pressure, for CO2melting point increases with increasing pressure. But all these processes must meet one condition, the line of change of environmental conditions must cut the saturation curve. for answering these questions is the observation that, in equilibrium, Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Supercritical steam is used at modern steam turbine power plants which are pursuing high efficiency. so-called The phase diagram for water is shown in the figure below. group, a theoretical framework for studying phase transitions, One of these special properties is the fact that solid water (ice) is less dense than liquid water just above the freezing point. As explained above Saturated steam is a condition in which water vapor has an equilibrium pressure and temperature with liquid water. This third curve is known as the saturated line. chemical potentials μ of the two phases are equal. The properties of supercritical water are very different from ambient liquid water. the Notice point \(E\), labeled the critical point. the remarkable physics, experimental and theoretical, that finally The critical point is a point that becomes the end of the liquid and gas phase equilibrium curve so that it can be in the same condition of pressure and temperature. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. The phase of water vapor can be classified again into three, saturated steam, superheated steam, and supercritical steam. [ "article:topic", "showtoc:no", "license:ccbync", "program:ck12" ]. Water is a unique substance in many ways. The research led to several Nobel prizes in 5 of the Longest Running Experiments in History, PharmTox Lab Rats Volume 5: Science Behind the Scenes, Australia Has a Flesh-Eating-Bacteria Problem, For The Last Time, No, A NASA Engineer Has Not Broken Physics With An Impossible Engine, Human skeletal stem cell can generate cartilage, bone, What the Creation of Exotic Matter on the ISS Means for the Future of Science. points where three phases such as solid-liquid-vapor or The boiler tube should be very resistant to thermal stress causing by the generation process of supercritical steam. This saturated steam diagram is made of a curve. For the right curve from the top of the curve to the lowest point is called the saturated steam curve. The heat of vaporization is zero. many problems beyond equilibrium phase transitions. Ice floats in liquid water. While the point on the saturated steam curve (hg) is the total enthalpy value required so that the water reaches 100% of steam. Case1: First, with fixed pressure, the environmental temperature is increased. End of the first curve is the Triple point of water. clarified why there are universal classes of critical exponents that In water’s diagram, the slope of the line between the solid and liquid states is negative rather than positive. The Phase Diagram of Water Figure \(\PageIndex{2}\) shows the phase diagram of water and illustrates that the triple point of water occurs at 0.01°C and 0.00604 atm (4.59 mmHg).