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

في الطبيعة ، توجد المادة في ثلاث مراحل: صلبة وسائلة وغازية. يتطلب الانتقال بين المراحل توازنا طوريا بين مرحلتين ويحدث عند درجة حرارة محددة لضغط معين.
يمكن تمثيل هذه الظروف بيانيا مع الضغط ودرجة الحرارة كمحاور ، والمعروفة باسم مخطط الطور.
يمثل مخطط الطور مراحل المادة التي تتعايش في توازن ديناميكي حراري وتخضع لانتقال الطور في ظل ظروف مختلفة ، مثل درجة الحرارة أو الضغط أو الحجم.
يوجد الماء في الطور السائل في درجة حرارة الغرفة والضغط الجوي. عند درجة حرارة 0درجةمئوية أو أقل ، تتغير الطور من سائل إلى صلب ، بينما عندما تكون درجة الحرارة أعلى من 100درجةمئوية ، فإنها تتغير إلى طور غازي.
يسمى الانتقال بين الصلب والغاز بالتسامي ، بينما تعرف التحولات من الصلب إلى السائل ومن السائل إلى الغاز باسم الاندماج والتبخر ، على التوالي.
تعرف النقطة التي تتعايش فيها المراحل الثلاث بالنقطة الثلاثية ، وتعرف النقطة التي تصبح فيها خصائص مرحلتين غير قابلة للتمييز بالنقطة الحرجة.

<ol>
	<li>OpenStax. (2019). جامعة الفيزياء المجلد 2. [نسخة الويب] ، الصفحة 37 - 38. تم الاسترجاع من<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>

منحنى الطور

<div style="direction:rtl">تعتمد مرحلة مادة معينة على الضغط ودرجة الحرارة. وبالتالي، فإن مخططات الضغط مقابل درجة الحرارة التي توضح الطور في كل منطقة توفر رؤى كبيرة حول الخواص الحرارية للمواد. تُعرف هذه المخططات باسم مخططات الطور. على سبيل المثال، في مخطط طور الماء (الشكل 1)، تشير حدود المنحنى الصلبة بين المراحل إلى التحولات الطورية (أي درجات الحرارة والضغوط التي تتعايش فيها المراحل). <img alt="Equation1" src="/files/ftp_upload/13673/13673_Figure_1v2.png" style="text-align: center; height: 300px;"> مع زيادة الضغط، ترتفع درجة حرارة غليان الماء تدريجيًا إلى 374 درجة مئوية عند ضغط 218 ضغط جوي. يمكن إثبات ذلك في قدر الضغط، الذي يطبخ الطعام بشكل أسرع من الوعاء المفتوح، لأن الماء يمكن أن يوجد كسائل عند درجات حرارة أكبر من 100 درجة مئوية دون أن يغلي بالكامل. وينتهي منحنى نقطة الغليان عند نقطة معينة تسمى النقطة الحرجة، وهي درجة الحرارة التي لا يمكن التمييز فوقها بين الطورين السائل والغازي؛ تسمى المادة بالسائل فوق الحرج. عند ضغط مرتفع بدرجة كافية فوق النقطة الحرجة، يكون للغاز كثافة السائل ولكنه لا يتكاثف. يُعرف الضغط عند هذه النقطة الحرجة بالضغط الحرج. ثاني أكسيد الكربون، على سبيل المثال، يكون في حالة فوق حرجة عند جميع درجات الحرارة التي تزيد عن 31.0 درجة مئوية، وهي النقطة التي تكون عندها المراحل الثلاث جميعها في حالة توازن. بالنسبة للمياه، تحدث النقطة الثلاثية عند 273.16 كلفن (0.01 درجة مئوية) و611.2 باسكال؛ وهذه درجة حرارة معايرة أكثر دقة من نقطة انصهار الماء عند 1.00 ضغط جوي، أو 273.15 كلفن (0.0 درجة مئوية).</div>

تعتمد مرحلة مادة معينة على الضغط ودرجة الحرارة. وبالتالي ، فإن مخططات الضغط مقابل درجة الحرارة تظهر المرحلة في كل منطقة ...

Education

JoVE Core

Physics

الفيزياء

Unit 1

الوحدة الأولى

The Kinetic Theory of Gases

النظرية الحركية للغازات

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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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kinetic theory of an ideal gas

Avogadro's Number and Gas Particle Motion

Avogadro's number and gas particle motion help explain how gases behave at the particle level. A mole is the amount of a substance that contains as many molecules as there are atoms in exactly 12 grams of carbon-12. This idea came from Amedeo Avogadro, who proposed that equal volumes of gas at the same pressure and temperature contain equal numbers of molecules, no matter what the gas is. Avogadro's number is the number of molecules in one mole. Its value is 6.02 × 10^23 mol−1. This number...

molecular kinetic energy

Gas Pressure and Molecular Motion

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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

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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...

escape velocities of gases

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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Water Phase Changes on a Pressure Chart

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