Name: gas pressure patterns in kinetic molecular theory
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 34 s
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Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

Le osservazioni delle diverse proprietà dei gas, espresse dalle varie leggi dei gas derivate da Boyle, Charles, Gay-Lussac e Avogadro, seguono concettualmente la teoria molecolare cinetica. La pressione esercitata da un gas risulta dall'impatto di particelle in continuo movimento sulle pareti del suo contenitore. Diminuendo il volume del contenitore, mantenendo costanti il numero di mole e la temperatura, le particelle di gas si avvicinano, riducendo la loro distanza fra le particelle.

In questo volume più piccolo, la densità del gas e la frequenza di collisione. La frequenza delle collisioni fra le pareti delle molecole.aumenta. Pertanto, la pressione esercitata dal gas aumenta.

La relazione inversa fra pressione e volume è data dalla legge di Boyle. L'aggiunta di più mole di gas al contenitore a temperatura costante aumenta la densità del gas e, quindi, la frequenza di collisione. Per mantenere la pressione iniziale, il volume deve espandersi.

Questa relazione diretta fra volume e mole è data dalla legge di Avogadro. Ora, consideriamo che il numero di mole viene mantenuto costante e la temperatura viene aumentata. Poiché l'energia cinetica media delle particelle di gas aumenta proporzionalmente alla temperatura, le particelle si scontrano più frequentemente e con maggiore forza.

Se il volume viene mantenuto costante mentre la temperatura viene aumentata, la densità del gas e la frequenza di collisione aumentano e dunque anche la pressione aumenta. La relazione diretta fra pressione e temperatura è data dalla legge di Gay-Lussac. Se invece la pressione rimane costante insieme ad un numero costante di moli, allora un aumento di temperatura deve essere accompagnato da un aumento di volume per diffondere le collisioni su una superficie maggiore.

Questa relazione diretta fra volume e temperatura viene data dalla legge di Charles. Infine, secondo la teoria molecolare cinetica, le particelle di gas non si attraggono né si respingono a vicenda. In una miscela di gas diversi, i componenti agiscono in modo indipendente e le loro pressioni individuali rimangono inalterate dalla presenza di un altro gas.

La pressione totale della miscela è quindi la somma delle singole pressioni parziali. Questa è la legge di Dalton.

la teoria molecolare cinetica e le leggi dei gas spiegano le propriet delle molecole di gas

La prova della teoria cinetica molecolare (KMT) e dei suoi postulati la sua capacit di spiegare e descrivere il comportamento di un gas. Le varie leggi dei gas (leggi di Boyle, Charles, Gay-Lussac, Avogadro e Dalton) possono essere derivate dalle ipotesi del KMT, che hanno portato i chimici a credere che le ipotesi della teoria rappresentino accuratamente le propriet delle molecole di gas.

La teoria cinetica molecolare spiega il comportamento dei gas.

Ricordiamo che la pressione del gas esercitata dalle molecole di gas in rapido movimento e dipende direttamente dal numero di molecole che colpiscono un'area unitaria della parete per unit di tempo, il KMT spiega concettualmente il comportamento di un gas come segue:

<ol style="list-style-type: disc;">
	<li>Legge di Gay-Lussac: se aumenta la temperatura, aumentano la velocit media e l’energia cinetica delle molecole del gas. Se il volume viene mantenuto costante, l'aumento della velocit delle molecole del gas provoca collisioni pi frequenti e pi forti con le pareti del contenitore, aumentando quindi la pressione. Questa anche definita legge di Amontons.</li>
	<li>Legge di Charles: Se la temperatura di un gas aumenta, la pressione pu essere mantenuta costante solo se aumenta il volume occupato dal gas. Ci si tradurr in maggiori distanze medie percorse dalle molecole per raggiungere le pareti del contenitore, nonch in una maggiore superficie delle pareti. Queste condizioni diminuiranno sia la frequenza delle collisioni molecola-parete sia il numero di collisioni per unit di area, i cui gli effetti combinati bilanciano l'effetto delle maggiori forze di collisione dovute alla maggiore energia cinetica alla temperatura pi elevata.</li>
	<li>Legge di Boyle: se il volume del gas diminuisce, l’area della parete del contenitore diminuisce e la frequenza di collisione molecola-parete aumenta, entrambi i quali aumentano la pressione esercitata dal gas.</li>
	<li>Legge di Avogadro: a pressione e temperatura costanti, la frequenza e la forza delle collisioni molecola-parete sono costanti. In tali condizioni, l'aumento del numero di molecole gassose richieder un aumento proporzionale del volume del contenitore per produrre una diminuzione del numero di collisioni per unit di area per compensare l'aumento della frequenza delle collisioni.</li>
	<li>Legge di Dalton: A causa delle grandi distanze tra loro, le molecole di un gas in una miscela bombardano le pareti del contenitore con la stessa frequenza, indipendentemente dalla presenza o meno di altri gas, e la pressione totale di una miscela di gas uguale alla somma delle (pressioni parziali) dei singoli gas.</li>
</ol>

Questo testo adattato da <a href="https://openstax.org/books/chemistry-2e/pages/9-5-the-kinetic-molecular-theory">Openstax, Chemistry 2e, Section 9.5: The Kinetic-Molecular Theory. </a>

La teoria molecolare cinetica e le leggi dei gas spiegano le propriet delle molecole di gas

La prova della teoria cinetica molecolare (KMT) e dei suoi postulati è la sua capacità di spiegare e descrivere il comportamento di un gas. Le varie leggi sui gas ...

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gas pressure patterns in kinetic molecular theory

Kinetic molecular theory explains gas pressure by linking it to the motion of gas molecules. Gas pressure comes from rapidly moving molecules hitting the walls of a container. It depends on how many molecules strike a unit area in a given time.

The theory also helps explain the main gas laws. In Gay-Lussac’s law, also called Amontons’s law, raising temperature increases the average speed and kinetic energy of gas molecules. If volume stays constant, the molecules collide with the walls more often and more forcefully, so pressure increases.

Charles’s law shows what happens when temperature rises at constant pressure. The gas must expand to keep pressure steady. That larger volume means molecules travel farther before reaching the walls, and the wall area increases too. These changes lower collision frequency and the number of collisions per unit area, which balances the stronger collisions caused by the higher kinetic energy.

Boyle’s law describes the effect of smaller volume. When gas volume decreases, the container wall area also decreases. Molecule-wall collisions become more frequent, and the pressure rises. Avogadro’s law says that at constant pressure and temperature, the collision rate and collision force stay constant. If the number of gas molecules increases, the volume must increase in proportion so the collisions per unit area can drop enough to offset the added molecules.

Dalton’s law applies to gas mixtures. Because gas molecules are far apart, one gas in a mixture strikes the container walls with the same frequency whether other gases are present or not. The total pressure of the mixture equals the sum of the partial pressures of the individual gases. These gas laws show how the assumptions of kinetic molecular theory fit the behavior of gases.

Gas Pressure Patterns in Kinetic Molecular Theory

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kinetic molecular theory and gas laws explain properties of gas molecules

Kinetic molecular theory explains gas pressure by linking it to the motion of gas molecules. Gas pressure comes from rapidly moving molecules hitting the walls of a container. It depends on how many molecules strike a unit area in a given time. The theory also helps explain the main gas laws. In Gay-Lussac’s law, also called Amontons’s law, raising temperature increases the average speed and kinetic energy of gas molecules. If volume stays constant, the molecules collide with the walls more...

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Explore how kinetic molecular theory explains gas pressure, temperature, volume changes, and the gas laws of Boyle, Charles, Gay-Lussac, Avogadro, and Dalton.

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Gas Pressure Patterns in Kinetic Molecular Theory

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