Name: kelvin temperature and gas thermometer standards
Uploaded: 2023-04-30T12:29:16.000Z
Duration: 1 min 22 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.13

CHEM.13.D

Gas Thermometers and the Kelvin Scale

يقوم مقياس حرارة الغاز بتقييم درجة الحرارة بناء على التغيرات في ضغط أو حجم الغاز المملوء.
هناك نوعان من موازين الحرارة الغازية: الحجم الثابت والضغط الثابت ، ومقياس حرارة الغاز ذو الحجم الثابت هو الأكثر استخداما.
مبدأ مقياس الحرارة هذا هو أنه عند الحجم الثابت ، يزداد ضغط الغاز مع زيادة درجة الحرارة.
لمعايرة مقياس حرارة الغاز ، يتم قياس الضغط عند 0 و 100 درجة مئوية.
يتم رسم هذه القيم في خط مستقيم ، والذي يتم استقراءه لإيجاد درجة حرارة الضغط الصفر.
درجة الحرارة هذه هي نقطة الصفر في مقياس كلفن. هذا هو المقياس القياسي لدرجة الحرارة ، حيث أن وحدة درجة الحرارة في النظام الدولي للوحدات هي كلفن.
الصفر المطلق هو أدنى درجة حرارة ممكنة تعكس بشكل مثالي الغياب التام للطاقة الحرارية.
على مقياس كلفن ، تبلغ نقطة تجمد الماء 273.15 ، بينما تبلغ نقطة الغليان 373.15. الفرق هو نفسه كما هو الحال في مقياس مئوية. فقط نقطة الصفر مختلفة.
وبالتالي ، يمكن بسهولة إنشاء العلاقة بين مقاييس كلفن ومئوية.

<ol>
	<li>OpenStax. (2019). جامعة الفيزياء المجلد 2. [نسخة الويب]. تم الاسترجاع من <a href="https://openstax.org/books/university-physics-volume-2/pages/1-2-thermometers-and-temperature-scales">https://openstax.org/books/university-physics-volume-2/pages/1-2-thermometers-and-temperature-scales</a></li>
</ol>

موازين الحرارة الغازية ومقياس كلفن

<div style="direction:rtl">يقترح تعريف درجة الحرارة من حيث الحركة الجزيئية أنه يجب أن تكون هناك أدنى درجة حرارة ممكنة، حيث يكون متوسط الطاقة الحركية للجزيئات صفرًا (أو الحد الأدنى الذي تسمح به ميكانيكا الكم). وتؤكد التجارب وجود درجة الحرارة هذه التي تسمى الصفر المطلق. مقياس درجة الحرارة المطلقة هو الذي تكون نقطة الصفر فيه هي الصفر المطلق. تعتبر هذه المقاييس ملائمة في العلوم لأن العديد من الكميات الفيزيائية، مثل حجم الغاز المثالي، ترتبط ارتباطًا مباشرًا بدرجة الحرارة المطلقة. مقياس كلفن هو مقياس درجة الحرارة المطلقة الشائع استخدامه في العلوم. يعد مقياس كلفن جزءًا من نظام الوحدات الدولي للوحدات، لذا فإن تعريفه الفعلي أكثر تعقيدًا من التعريف المذكور أعلاه. أولاً، لم يتم تعريفها من حيث درجتي تجمد وغليان الماء، بل من حيث النقطة الثلاثية. النقطة الثلاثية هي مزيج فريد من درجة الحرارة والضغط الذي يمكن أن يتعايش فيه الجليد والماء السائل وبخار الماء بشكل ثابت. يتم تعريف درجة حرارة النقطة الثلاثية على أنها 273.16 كلفن. ويتميز هذا التعريف بأنه على الرغم من أن درجة حرارة التجمد ودرجة حرارة غليان الماء تعتمد على الضغط، إلا أن هناك درجة حرارة نقطة ثلاثية واحدة فقط. حتى مع وجود نقاط محددة جيدًا على المقياس، فإن موازين الحرارة المختلفة تعطي نتائج مختلفة إلى حد ما بالنسبة لدرجات الحرارة الأخرى. لذلك، هناك حاجة إلى مقياس حرارة قياسي. وقد اختار علماء القياس مقياس حرارة الغاز ذو الحجم الثابت لهذا الغرض. يتعرض وعاء ذو حجم ثابت مملوء بالغاز لتغيرات في درجة الحرارة، وتتناسب درجة الحرارة المقاسة مع التغير في الضغط. تعتمد النتائج إلى حد ما على اختيار الغاز، ولكن كلما كانت كثافة الغاز أقل في المصباح، كانت النتائج أفضل بالنسبة للغازات المختلفة. إذا تم استقراء النتائج إلى كثافة صفر، فإن النتائج تتفق جيدًا، مع ضغط صفر يتوافق مع درجة حرارة الصفر المطلق. تعتبر موازين الحرارة الغازية ذات الحجم الثابت كبيرة الحجم وتصل إلى التوازن ببطء، لذلك يتم استخدامها في الغالب كمعايير لمعايرة موازين الحرارة الأخرى.</div>

يشير تعريف درجة الحرارة من حيث الحركة الجزيئية إلى أنه يجب أن تكون هناك أدنى درجة حرارة ممكنة ، حيث يكون متوسط الطاقة الحركية ...

Education

JoVE Core

Physics

الفيزياء

Unit 1

الوحدة الأولى

Temperature and Heat

درجة الحرارة والحرارة

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

kelvin temperature and gas thermometer standards

Kelvin temperature is the absolute scale used in science, and it starts at absolute zero. That zero point matches the lowest possible temperature, where molecular motion reaches zero or the minimum allowed by quantum mechanics. Scientists use this scale because some physical quantities, such as the volume of an ideal gas, depend directly on absolute temperature.

The Kelvin scale is part of the SI system of units, so its definition is more precise than simply using water’s freezing and boiling points. Instead, it is tied to the triple point of water. The triple point is the only temperature and pressure combination where ice, liquid water, and water vapor can all coexist. Its temperature is defined as 273.16 K, which is useful because it does not change with pressure the way water’s freezing and boiling points do.

Even with fixed reference points, different thermometers can give slightly different readings for other temperatures. For that reason, scientists need a standard thermometer. Metrologists use the constant-volume gas thermometer for this job. In this device, a gas in a sealed vessel stays at the same volume while temperature changes, and the temperature is found from the change in pressure.

The choice of gas can affect the results a little. However, the less dense the gas in the bulb, the better different gases agree. When the results are extrapolated to zero density, they match well, and zero pressure corresponds to absolute zero. Constant-volume gas thermometers are large and slow to reach equilibrium, so they are mainly used as standards to calibrate other thermometers.

Kelvin Temperature and Gas Thermometer Standards

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gas thermometers and the kelvin scale

Kelvin temperature is the absolute scale used in science, and it starts at absolute zero. That zero point matches the lowest possible temperature, where molecular motion reaches zero or the minimum allowed by quantum mechanics. Scientists use this scale because some physical quantities, such as the volume of an ideal gas, depend directly on absolute temperature. The Kelvin scale is part of the SI system of units, so its definition is more precise than simply using water’s freezing and boiling...

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Heat is energy transferred because of a temperature difference, and it can change an object’s temperature. Since heat is energy, its SI unit is the joule (J). Heat transfer is the movement of energy from one place or material to another, and it plays a role in home heating, cooking, and many industrial processes. Two common units for heat are the calorie and the kilocalorie. A calorie (cal) is the energy needed to change the temperature of 1 g of water by 1 °C, specifically between 14.5 °C and...

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Calorimetry studies heat exchange in an insulated system. A calorimeter is a container that prevents heat transfer in or out. Scientists use calorimetry to measure heat and specific heat capacity. A calorimetry problem is any situation where the objects are thermally isolated from their surroundings. The key idea comes from conservation of energy. During heat transfer, the heat gained by the colder object must equal the heat lost by the hotter object. A simple example is water poured into a...

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Heat transfer happens when there is a temperature difference. It can move fast, like through a cooking pan, or slowly, like through the walls of a picnic ice box. Heat transfer appears in many everyday situations, so it is hard to find a place where it does not occur. There are only three ways heat is transferred: conduction, convection, and radiation. A fireplace shows all three at once. Radiation carries most of the heat into the room. Conduction also moves heat into the room, but much more...

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Convection and radiation are two major ways heat moves. In convection, thermal energy is carried by the large-scale flow of matter. Warm air and water rise because they are less dense, so ocean currents and large-scale atmospheric circulation move heat from the tropics toward the poles and move cold air from the poles toward the tropics. Earth’s rotation changes these moving air currents. It interacts with the flow and helps produce the eastward movement of air in the temperate zones.

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Earth’s energy balance and the greenhouse effect help explain its average temperature. Earth is in radiative contact with both the Sun and dark space. It receives almost all of its energy from solar radiation, and it reflects some of that energy back into outer space. Dark space is very cold, about 3 K, so Earth also radiates energy into it. Heat can move quickly from soil and grasses, and frost can form on clear summer evenings, even in warm latitudes. In a first approximation, Earth’s...

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Radiation heat transfer depends on temperature, surface area, and emissivity. The Stefan-Boltzmann law describes the rate of heat transfer by emitted radiation. In this law, σ is the Stefan-Boltzmann constant, A is the object’s surface area, and T is its temperature in kelvins. The fourth-power dependence on absolute temperature makes radiation highly sensitive to small temperature changes. Even a slight rise in temperature can change the emitted heat a lot. That sensitivity is why radiation...

key terms and concepts

Learn how the Kelvin scale is tied to absolute zero, the triple point of water, and constant-volume gas thermometers used to calibrate other thermometers.

Kelvin Temperature and Gas Thermometer Standards | JoVE K12

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Kelvin Temperature and Gas Thermometer Standards

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