Name: water phase changes on a pressure chart
Uploaded: 2025-05-22T09:05:49.000Z
Duration: 1 min 19 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Physical Science

SC.912.P.12

SC.912.P.12.11

Phase Diagram

W przyrodzie materia występuje w trzech fazach: stałej, ciekłej i gazowej. Przejście między fazami wymaga równowagi fazowej między dwiema fazami i zachodzi w określonej temperaturze dla danego ciśnienia.
Warunki te można przedstawić graficznie z ciśnieniem i temperaturą jako osiami, znanymi jako diagram fazowy.
Diagram fazowy przedstawia fazy substancji, które współistnieją w równowadze termodynamicznej i przechodzą przemianę fazową w różnych warunkach, takich jak temperatura, ciśnienie lub objętość.
Woda występuje w fazie ciekłej w temperaturze pokojowej i ciśnieniu atmosferycznym. W temperaturze 0oC lub niższej faza przechodzi z ciekłej w stałą, natomiast gdy temperatura przekracza 100oC, przechodzi w fazę gazową.
Przejście między ciałem stałym a gazem nazywa się sublimacją, podczas gdy przejścia ze stanu stałego do ciekłego i z cieczy do gazu są znane odpowiednio jako fuzja i parowanie.
Punkt, w którym wszystkie trzy fazy współistnieją, jest znany jako punkt potrójny, a punkt, w którym właściwości dwóch faz stają się nierozróżnialne, jest znany jako punkt krytyczny.

<ol>
	<li>Protokół OpenStax. (2019). Fizyka uniwersytecka Vol. 2. [Wersja internetowa], str. 37 - 38. Pobrane z<a href="https://openstax.org/books/university-physics-volume-2/pages/1-5-phase-changes">https://openstax.org/books/university-physics-volume-2/pages/1-5-phase-changes</a></li>
</ol>

diagram fazowy

Faza danej substancji zależy od ciśnienia i temperatury. Zatem wykresy ciśnienia w funkcji temperatury pokazujące fazę w każdym obszarze zapewniają znaczny wgląd w właściwości termiczne substancji. Takie wykresy nazywane są diagramami fazowymi. Na przykład na diagramie fazowym wody (rysunek 1) granice krzywych ciągłych pomiędzy fazami wskazują przejścia fazowe (tj. temperatury i ciśnienia, w których fazy współistnieją).

<img alt="Równanie1" src="/files/ftp_upload/13673/13673_Figure_1v2.png" style="text-align: center; height: 300px;" />

Wraz ze wzrostem ciśnienia temperatura wrzenia wody wzrasta stopniowo do 374 °C przy ciśnieniu 218 atm. Można to wykazać na przykładzie szybkowaru, który gotuje żywność szybciej niż w otwartym garnku, ponieważ woda może istnieć w postaci cieczy w temperaturach wyższych niż 100°C bez całkowitego wygotowania. Krzywa temperatury wrzenia kończy się w pewnym punkcie zwanym punktem krytycznym, czyli temperaturą, powyżej której nie można rozróżnić fazy ciekłej i gazowej; substancja nazywa się płynem nadkrytycznym. Przy wystarczająco wysokim ciśnieniu powyżej punktu krytycznego gaz ma gęstość cieczy, ale nie skrapla się. Ciśnienie w tym punkcie krytycznym nazywa się ciśnieniem krytycznym. Na przykład dwutlenek węgla jest nadkrytyczny we wszystkich temperaturach powyżej 31,0°C, czyli punktu, w którym wszystkie trzy fazy istnieją w równowadze. W przypadku wody punkt potrójny występuje przy 273,16 K (0,01 ° C) i 611,2 Pa; jest to dokładniejsza temperatura kalibracji niż temperatura topnienia wody przy 1,00 atm, czyli 273,15 K (0,0 ℃).

Diagram fazowy

Faza danej substancji zależy od ciśnienia i temperatury. Tak więc wykresy ciśnienia w funkcji temperatury pokazujące fazę w każdym regionie ...

Education

JoVE Core

Physics

Fizyka

Unit 1

Jednostka 1

The Kinetic Theory of Gases

Kinetyczna teoria gazów

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

water phase changes on a pressure chart

Water phase changes can be mapped on a pressure and temperature chart called a phase diagram. These plots show which phase a substance is in at different conditions. They also reveal where phase transitions happen, because the boundary lines mark the temperatures and pressures where two phases coexist.

The water phase diagram shows how pressure affects boiling. As pressure rises, the boiling temperature increases gradually until it reaches 374 °C at 218 atm. A pressure cooker works this way. It lets water stay liquid above 100 °C, so food cooks faster than it would in an open pot.

The boiling-point curve ends at the critical point. Above this temperature, the liquid and gas phases can no longer be told apart. The substance is then called a supercritical fluid. At pressures above the critical point, a gas can have the density of a liquid without condensing.

The pressure at the critical point is called the critical pressure. Carbon dioxide becomes supercritical at all temperatures above 31.0 °C. That is also the point where solid, liquid, and gas exist together in equilibrium.

Water also has a triple point. It occurs at 273.16 K, or 0.01 °C, and 611.2 Pa. This point is useful in science because it is a more accurate calibration temperature than the melting point of water at 1.00 atm, which is 273.15 K, or 0.0 °C.

Water Phase Changes on a Pressure Chart

equation of state

Gas Behavior in the Equation of State

The equation of state describes how a gas’s pressure, volume, temperature, and number of moles are related. These macroscopic properties help define the condition, or state, of the matter in a thermodynamics system. The relationship between these quantities can be written as a simple mathematical expression. In some cases, it is too complex to express in a formula. Even then, the link between the quantities still exists. When an equation of state cannot be written mathematically, scientists...

ideal gas equation

Gas Laws Behind the Ideal Equation

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van der waals equation

How Real Gases Deviate from Ideal Behavior

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Liquid-Gas Changes on pV Curves

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distribution of molecular speeds

Molecular Speed Curves and Vapor Pressure

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maxwell-boltzmann-distribution-problem-solving

Maxwell-Boltzmann Gas Speed Ratio

The Maxwell-Boltzmann distribution describes how molecular speeds are spread in a gas. Even though individual molecules move in random directions, the whole gas has a predictable speed pattern. This distribution is written as f(v), where v is molecular speed. The distribution function is used to find the expected number of particles with speeds between v1 and v2. Because N is dimensionless, f(v) has units of seconds per meter. The relationship can also be written in differential form for speed...

phase diagram

Water phase changes can be mapped on a pressure and temperature chart called a phase diagram. These plots show which phase a substance is in at different conditions. They also reveal where phase transitions happen, because the boundary lines mark the temperatures and pressures where two phases coexist. The water phase diagram shows how pressure affects boiling. As pressure rises, the boiling temperature increases gradually until it reaches 374 °C at 218 atm. A pressure cooker works this way.

mean free path and mean free time

Gas collisions: path length and time

Gas collisions in a cylinder help explain the mean free path and mean free time. Gas molecules move in random motion. They collide with each other and change speed and direction. The mean free path is the average path length between collisions. The mean free path depends on how many molecules are packed into a volume. It varies inversely with density. When more molecules are present, collisions happen more often, so the mean free path becomes shorter. It also depends on molecule size. Larger...

heat capacity: problem-solving

Heat Capacity of Gases by Degrees of Freedom

Heat capacity of gases depends on the gas type and the motion of its molecules. It is the amount of heat energy needed to raise the temperature of a unit mass of gas by one degree Celsius. This thermodynamic property is important in science and industry. To solve heat capacity problems, first identify the gas. A gas's molecular structure affects its heat capacity because the molecules have different degrees of freedom. These values can be found from tables or from empirical equations. Next,...

dalton's law of partial pressure

Gas Mixtures and Their Partial Pressures

Gas mixtures have a total pressure that comes from the partial pressures of each gas. A partial pressure is the pressure one gas would make if it filled the whole container by itself. This idea helps explain how gases behave when they are mixed together. When two or more gases share a container, their molecules move randomly and collide with one another. If the gases are at the same temperature, they reach thermal equilibrium. Their molecules then have the same average kinetic energy. In that...

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Why Lighter Gases Escape Earth First

Earth’s escape velocity is the speed an object needs to leave gravity behind. Near the top of the atmosphere, about 100 km above Earth, that speed is 11.1 km/s. Gas molecules can escape only if their speeds become high enough to reach that limit. The chance of escape depends on gas temperature and molecular speed. According to kinetic theory, the average kinetic energy of gas molecules is proportional to temperature. As temperature rises, the rms speed, or root-mean-square speed, also rises.

key terms and concepts

Explore how water changes phase with pressure and temperature, including boiling point shifts, the critical point, supercritical fluids, and the triple point.

Water Phase Changes on a Pressure Chart | JoVE K12

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A. Motion can be measured and described qualitatively and quantitatively. Net forces create a change in motion. When objects travel at speeds comparable to the speed of light, Einstein's special theory of relativity applies.

B. Momentum is conserved under well-defined conditions. A change in momentum occurs when a net force is applied to an object over a time interval.

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E. Chemical reaction rates change with conditions under which they occur. Chemical equilibrium is a dynamic state in which forward and reverse processes occur at the same rates.

Water Phase Changes on a Pressure Chart

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