critical pressure

Examples of critical pressure in the following topics:

• Supercritical Fluids

  • A supercritical fluid is a substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist.
  • On the other hand, high enough pressures (above the critical pressure) would not allow a sample to stay in the pure gaseous state.
  • The critical point of a binary mixture can be estimated as the arithmetic mean of the critical temperatures and pressures of the two components,
  • Thus, above the critical temperature a gas cannot be liquified by pressure.
  • At slightly above the critical temperature (310 K), in the vicinity of the critical pressure, the line is almost vertical.

• Interpreting Phase Diagrams

  • Phase diagrams can also be used to explain the behavior of a pure sample of matter at the critical point.
  • General observations from the diagram reveal that certain conditions of temperature and pressure favor certain phases of matter.
  • The critical point, which occurs at critical pressure (Pcr) and critical temperature (Tcr), is a feature that indicates the point in thermodynamic parameter space at which the liquid and gaseous states of the substance being evaluated are indistinguishable.
  • At temperatures above the critical temperature, the kinetic energy of the molecules is high enough so that even at high pressures the sample cannot condense into the liquid phase.
  • A typical phase diagram illustrating the major components of a phase diagram as well as the critical point.

• Three States of Matter

  • The highest temperature at which a particular liquid can exist is called its critical temperature.
  • A liquid can be converted to a gas through heating at constant pressure to the substance's boiling point or through reduction of pressure at constant temperature.
  • A gas at a temperature below its critical temperature can also be called a vapor.
  • It can also exist in equilibrium with a liquid (or solid), in which case the gas pressure equals the vapor pressure of the liquid (or solid).
  • A supercritical fluid (SCF) is a gas whose temperature and pressure are greater than the critical temperature and critical pressure.

• Pressure in the Body

  • Pressure plays an essential role in a number of critical bodily functions including respiration and blood circulation.
  • Pressure plays an essential role in various critical bodily systems that are necessary for survival.
  • One such critical bodily system which relies on pressure for functionality is the circulatory system, which is an example of a closed fluid system under pressure.
  • In practice, the mean arterial pressure (MAP) can be approximated from easily obtainable blood pressure measurements in , where Psys is the measured systolic pressure and Pdias is the measured diastolic pressure.
  • In practice, the mean arterial pressure (MAP) can be approximated from easily obtainable blood pressure measurements.

• Why do businesses greenwash

  • An attempt to divert the attention of regulators and reduce pressure for regulatory change,
  • The desire to persuade critics that they're well intentioned and/or have changed their ways,

• Phase Changes and Energy Conservation

  • 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).
  • As the pressure increases, the boiling temperature rises steadily to 374º C at a pressure of 218 atm.
  • The curve ends at a point called the critical point, because at higher temperatures the liquid phase does not exist at any pressure.
  • The critical temperature for oxygen is -118ºC, so oxygen cannot be liquefied above this temperature.
  • Note that water changes states based on the pressure and temperature.

• Real Gases

  • Equations other than the Ideal Gas Law model the non-ideal behavior of real gases at high pressures and low temperatures.
  • At a certain point of combined low temperature and high pressure, real gases undergo a phase transition from the gaseous state into the liquid or solid state.
  • Real-gas models must be used near the condensation point of gases (the temperature at which gases begin to form liquid droplets), near critical points, at very high pressures, and in other less common cases.
  • The graph below depicts how the compressibility factor varies with increasing pressure for a generalized graph.
  • According to the Ideal Gas Equation, PV=nRT, pressure and volume should have an inverse relationship.

• Short-Term Neural Control

  • The autonomic nervous system plays a critical role in the regulation of vascular homeostasis.
  • They send impulses to the cardiovascular centre to regulate blood pressure.
  • Combined, these activities cause blood pressure to fall.
  • Combined, these activities cause blood pressure to rise.
  • Increased blood pressure results in increased rates of baroreceptor firing, whereas decreased blood pressure results in slower rates of fire, both initiating the homeostatic mechanism to restore blood pressure.

• Gauge Pressure and Atmospheric Pressure

  • Pressure is often measured as gauge pressure, which is defined as the absolute pressure minus the atmospheric pressure.
  • Gauge pressure is a relative pressure measurement which measures pressure relative to atmospheric pressure and is defined as the absolute pressure minus the atmospheric pressure.
  • Most pressure measuring equipment give the pressure of a system in terms of gauge pressure as opposed to absolute pressure.
  • For example, tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute.
  • Explain the relationship among absolute pressure, gauge pressure, and atmospheric pressure

• Measuring Blood Pressure

  • Measurement of blood pressure includes systolic pressure during cardiac contraction and diastolic pressure during cardiac relaxation.
  • Blood pressure is the pressure blood exerts on the arterial walls.
  • These pressures are called segmental blood pressures and are used to evaluate blockage or arterial occlusion in a limb (for example, the ankle brachial pressure index).The difference between the systolic and diastolic pressure is called the pulse pressure.
  • A blood pressure cuff and associated monitor used for determining systolic and diastolic pressures within an artery.
  • Explain how blood pressure is measured and the ranges of blood pressure readings