phase diagram

(noun)

A graph showing the phase a sample of matter has under different conditions of temperature and pressure.

Related Terms

  • T
  • dipole
  • amphoteric
  • equilibrium

Examples of phase diagram in the following topics:

  • Major Features of a Phase Diagram

    • A phase diagram is a graph which shows under what conditions of temperature and pressure distinct phases of matter occur.
    • The simplest phase diagrams are of pure substances.
    • The major features of a phase diagram are phase boundaries and the triple point.
    • The phase diagram for water is useful for learning how to analyze these diagrams.
    • In this phase diagram, which is typical of most substances, the solid lines represent the phase boundaries.
  • Interpreting Phase Diagrams

    • Phase diagrams illustrate the effects selected variables of a system have on the state of matter.
    • Phase diagrams illustrate the effects selected variables of a system have on the state of matter.
    • When evaluating the phase diagram, it is worth noting that the solid-liquid phase boundary in the phase diagram of most substances has a positive slope.
    • With a knowledge of the major components of phase diagrams and the features of phase plots, a phase diagram can be used to understand how altering thermodynamic parameters influences the states/phases of matter a sample of a substance is in.
    • A typical phase diagram illustrating the major components of a phase diagram as well as the critical point.
  • Solid to Gas Phase Transition

    • Sublimation is the phase transition from the solid to the gaseous phase, without passing through an intermediate liquid phase.
    • Sublimation is the process of transformation directly from the solid phase to the gaseous phase, without passing through an intermediate liquid phase.
    • It is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point (the temperature and pressure at which all three phases coexist) in its phase diagram.
    • But at temperatures below that of the triple point, a decrease in pressure will result in a phase transition directly from the solid to the gaseous.
    • At temperatures and pressures below those of the triple point, a phase change between the solid and gas phases can take place.
  • Phase Changes and Energy Conservation

    • A phase of a thermodynamic system and the states of matter have uniform physical properties.
    • There are well-defined regions on these graphs that correspond to various phases of matter, so PT graphs are called phase diagrams .
    • Using the graph, if you know the pressure and temperature you can determine the phase of water.
    • The solid lines—boundaries between phases—indicate temperatures and pressures at which the phases coexist (that is, they exist together in ratios, depending on pressure and temperature).
    • In this typical phase diagram of water, the green lines mark the freezing point, and the blue line marks the boiling point, showing how they vary with pressure.
  • Supercritical Fluids

    • In the pressure-temperature phase diagram of CO2, the boiling separates the gas and liquid region and ends in the critical point, where the liquid and gas phases disappear to become a single supercritical phase.
    • The system consists of 2 phases in equilibrium, a dense liquid and a low density gas.
    • At the critical point, (304.1 K and 7.38 MPa) there is no difference in density, and the two phases become one fluid phase.
    • The dry ice melts under high pressure, and forms a liquid and gas phase.
    • When the vessel is heated, the CO2 becomes supercritical -- meaning the liquid and gas phases merge together into a new phase that has properties of a gas, but the density of a liquid.
  • The Structure and Properties of Water

    • Its liquid phase, the most common phase of water on Earth, is the form that is generally meant by the word "water."
    • When water achieves a specific critical temperature and a specific critical pressure (647 K and 22.064 MPa), the liquid and gas phases merge into one homogeneous fluid phase that shares properties of both gas and liquid.
    • Phase diagrams help describe how water changes states depending on the pressure and temperature.
    • During the phase transition between two phases (i.e, along these boundaries), the phases are in equilibrium with each other.
    • The three phases of water – liquid, solid, and vapor – are shown in temperature-pressure space.
  • Capacitors in AC Circuits: Capacitive Reactance and Phasor Diagrams

    • Due to the phase difference, it is useful to introduce phasors to describe these circuits.
    • We say that the current and voltage are in phase.
    • In the diagram, the arrows rotate in counter-clockwise direction at a frequency $\nu$.
    • Its amplitude is the modulus of the vector, and its argument is the total phase \omega t+\theta.
    • The phase constant \theta represents the angle that the vector forms with the real axis at t = 0.
  • Power

    • Here, $\phi$ is called the phase angle.
    • As seen in previous Atoms, voltage and current are out of phase in an RLC circuit.
    • There is a phase angle ϕ between the source voltage V and the current I, given as
    • Phasor diagram for an RLC series circuit.
    • \phi is the phase angle, equal to the phase difference between the voltage and current.
  • Bond Order

    • This MO diagram depicts the molecule H2, with the contributing AOs on the outside sandwiching the MO.
    • The third diagram hypothesizes the molecule dihelium (He2).
    • However, removing an electron from the antibonding level produces the molecule He2+, which is stable in the gas phase with a bond order of 0.5.
    • The last diagram presents the molecule dilithium (Li2).
    • The molecule Li2 is a stable molecule in the gas phase, with a bond order of one.
  • Bonding and Antibonding Molecular Orbitals

    • Bonding and antibonding orbitals are illustrated in MO diagrams, and are useful for predicting the strength and existence of chemical bonds.
    • Two atomic orbitals can overlap in two ways, depending on their phase relationship.
    • An orbital's phase is a direct consequence of electrons' wave-like properties.
    • If the phase changes, the bond becomes a pi bond (π-bond).
    • The next step in constructing an MO diagram is filling the newly formed molecular orbitals with electrons.
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