Name: why lighter gases escape earth first
Uploaded: 2023-09-18T17:11:17.000Z
Duration: 1 min 19 s
Channel: JoVE

Kaçış hızı, itilmemiş bir cismin birincil cismin yerçekimi kuvvetinin etkisinden kaçması için gereken minimum hızdır. Dünya'nın kaçış hızının büyüklüğü 11.1 km/s'dir.
Hidrojen moleküllerinin Dünya'nın kaçış hızına eşit rms hızına ulaştığı sıcaklık nedir?
Gazların kinetik teorisine göre, herhangi bir gazın ortalama kinetik enerjisi sıcaklığı ile ilgilidir. Hidrojen moleküllerinin kütlesi, molar kütlesinin Avogadro sayısına oranı alınarak hesaplanabilir.
Şimdi, kinetik enerji denklemini yeniden düzenleyerek ve bilinen miktarları yerine koyarak, kaçış hızına ulaşmak için gereken sıcaklık hesaplanır.
Tahmini sıcaklık, Dünya atmosferinin yüksek irtifalarındaki sıcaklıktan birkaç kat daha yüksektir. Bu, hidrojen moleküllerinin Dünya atmosferinden kaçamayacağı anlamına gelir.
Bununla birlikte, çoklu çarpışmalar sırasında, önemli hidrojen molekülleri, Dünya atmosferinden hidrojen kaybına izin veren kaçış hızına ulaşır.

<ol>
	<li>Stax'ı açın. (2019). Üniversite Fiziği Cilt 2. [Web sürümü]. Bölüm 2.2'den alındı; Sayfa 83-84. <a href="https://openstax.org/books/university-physics-volume-2/pages/2-2-pressure-temperature-and-rms-speed">2.2 Basınç, Sıcaklık ve RMS Hızı - Üniversite Fiziği Cilt 2 | OpenStax (Stax)</a></li>
</ol>

gazların kaçma hızları

Escape Velocities of Gases

Dünya'nın yerçekiminden kaçmak için atmosferin üstünde, 100 km yükseklikteki bir nesne, Dünya'dan 11.1 km/s hızla uzaklaşmalıdır. Bu hıza kaçma hızı denir. Gaz moleküllerinin ortalama kinetik enerjisinin eşit olduğu rms hızına ulaşıldığı sıcaklık, gaz moleküllerinin ortalama kinetik enerjisi denklemi kullanılarak tahmin edilebilir. Gazların kinetik teorisine göre, gaz moleküllerinin ortalama kinetik enerjisi sıcaklığına orantılıdır. Sıcaklık ne kadar yüksekse, gaz moleküllerinin rms hızı da o kadar yüksek olur.

Hidrojen molekülleri için, kaçma hızına eşit olan rms hızı 99.7 x 102 K sıcaklıkta elde edilir. Bu sıcaklık, Dünya'nın yüzeyinden 100 km yükseklikteki sıcaklığa kıyasla birkaç büyüklük değişimi daha yüksektir. Bu gibi yüksekliklerde sıcaklık yaklaşık olarak 250 K'dır. Bu basitçe hidrojen moleküllerinin Dünya atmosferinden kaçma olasılığının ihmal edilebilir olduğu anlamına gelir. Ancak, tersine, Dünya atmosferinde çok az miktarda hidrojen molekülü kalmaktadır. Hidrojen kaybı, bazı moleküllerin normal sıcaklıklarda bile Dünya'nın kaçma hızından daha yüksek hızlara sahip olmasından kaynaklanır. Bir hidrojen molekülünün hızı bir çarpışmadan diğerine değişir; dolayısıyla, herhangi bir anda molekülün hızının kaçma hızından daha yüksek olma olasılığı küçük ama varolabilir bir şanstır. Bu olasılık yeterince yüksektir ki Dünya'nın ömrü boyunca atmosferdeki neredeyse tüm hidrojen molekülleri yüksek irtifalardaki kaçma hızına ulaşmış ve Dünya'nın yerçekiminden kaçmıştır.

Ancak, oksijen, azot ve su gibi daha ağır moleküllerin rms hızları daha düşüktür, bu yüzden onlardan herhangi birinin kaçma hızından daha yüksek hızlara sahip olması çok daha az olasıdır. Olasılık o kadar küçüktür ki atmosferden önemli miktarda ağır moleküllerin kaybedilmesi için milyarlarca yıl gerekmektedir. Ay'ın atmosferinin olmaması da aynı kavramı kullanarak açıklanabilir. Ay'ın yerçekimi çekimi çok daha zayıf olduğu için neredeyse tüm atmosferini kaybetmiştir.

Gazların Kaçma Hızları

Dünya'nın yerçekiminden kaçmak için, 100 km yükseklikte atmosferin tepesine yakın bir nesnenin Dünya'dan 11.1 km/s hızla uzaklaşması gerekir. Bu hız ...

Education

JoVE Core

Physics

Fizik

Unit 1

Ünite 1

The Kinetic Theory of Gases

Gazların Kinetik Teorisi

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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. For hydrogen molecules, the temperature needed for rms speed to match escape velocity is 99.7 x 10 2 K.

That temperature is far above the temperature at 100 km altitude, which is about 250 K. So under normal conditions, the chance of hydrogen molecules escaping Earth’s atmosphere is very small. Even so, a few hydrogen molecules are still lost over time. Their speeds change from one collision to the next, so at any moment some molecules can move faster than escape velocity.

Over Earth’s lifetime, that small chance has been enough for almost all hydrogen molecules to escape from the atmosphere. Heavier molecules such as oxygen, nitrogen, and water move more slowly on average. That makes it much less likely that they will exceed escape velocity. Because of this, billions of years are needed to lose large amounts of these heavier gases.

The Moon shows the same idea in a stronger way. Its gravitational pull is much weaker than Earth’s. As a result, it has lost almost its entire atmosphere.

Why Lighter Gases Escape Earth First

equation of state

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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

Gas pressure comes from the motion of molecules in a container. The word gas came from a Flemish word meaning “chaos,” and J. B. van Helmont first used it to describe vapors. In a gas, molecules move in a continuous and random way. When a molecule hits a container wall, its velocity changes. The part of the velocity parallel to the wall stays the same. The part perpendicular to the wall reverses direction, but its size does not change. If the molecule’s velocity changes in the x-direction, its...

distribution of molecular speeds

Molecular Speed Curves and Vapor Pressure

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maxwell-boltzmann-distribution-problem-solving

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phase diagram

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mean free path and mean free time

Gas collisions: path length and time

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escape velocities of gases

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 escape velocity, temperature, and molecular speed affect atmospheric loss. See why hydrogen escapes more easily than heavier gases.

Why Lighter Gases Escape Earth First | JoVE K12

physics

JoVE Temel Fizik, kinematik, dinamik, akışkanlar mekaniği, statik, dalgalar ve akustik dahil olmak üzere temel fizik konularının teorisini ve uygulamasını kısa ve anlaşılması kolay animasyonlu videolarla tanıtıyor. Ek olarak, sektör içindeki bilim insanı videoları, dünya çapındaki günümüz laboratuvarlarında gerçekleştirilen klasik ve orijinal araştırma deneylerinde ilgili kavramların uygulanmasını göstermektedir.

Why Lighter Gases Escape Earth First

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