{"id":48372,"date":"2019-11-10T07:06:20","date_gmt":"2019-11-10T06:06:20","guid":{"rendered":"https:\/\/www.thermal-engineering.org\/o-que-e-energia-interna-do-gas-ideal-gas-monatomico-molecula-diatomica-definicao\/"},"modified":"2020-01-28T15:31:19","modified_gmt":"2020-01-28T14:31:19","slug":"o-que-e-energia-interna-do-gas-ideal-gas-monatomico-molecula-diatomica-definicao","status":"publish","type":"post","link":"https:\/\/www.thermal-engineering.org\/pt-br\/o-que-e-energia-interna-do-gas-ideal-gas-monatomico-molecula-diatomica-definicao\/","title":{"rendered":"O que \u00e9 energia interna do g\u00e1s ideal – g\u00e1s monat\u00f4mico, mol\u00e9cula diat\u00f4mica – defini\u00e7\u00e3o"},"content":{"rendered":"
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A energia interna \u00e9 o total de toda a energia associada ao movimento dos \u00e1tomos ou mol\u00e9culas no sistema e \u00e9 variada para gases monat\u00f4micos e mol\u00e9culas diat\u00f4micas.\u00a0Engenharia T\u00e9rmica<\/div>\n<\/div>\n
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Energia interna de um g\u00e1s ideal<\/h2>\n

A\u00a0energia interna<\/strong><\/a>\u00a0\u00e9 o total de toda a energia associada ao movimento dos \u00e1tomos ou mol\u00e9culas no sistema.\u00a0As formas microsc\u00f3picas<\/strong>\u00a0de energia incluem aquelas devidas \u00e0\u00a0rota\u00e7\u00e3o<\/strong>\u00a0,\u00a0vibra\u00e7\u00e3o<\/strong>\u00a0,\u00a0tradu\u00e7\u00e3o<\/strong>\u00a0e\u00a0intera\u00e7\u00f5es<\/strong>\u00a0entre as mol\u00e9culas de uma subst\u00e2ncia.<\/p>\n<\/div>\n<\/div>\n

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G\u00e1s Monat\u00f4mico – Energia Interna<\/h2>\n

Para um\u00a0g\u00e1s ideal monat\u00f4mico<\/strong>\u00a0(como h\u00e9lio, n\u00e9on ou arg\u00f4nio), a \u00fanica contribui\u00e7\u00e3o para a energia vem da\u00a0energia cin\u00e9tica translacional<\/strong>\u00a0.\u00a0A energia cin\u00e9tica translacional m\u00e9dia de um \u00fanico \u00e1tomo depende\u00a0apenas<\/strong>\u00a0da\u00a0temperatura<\/strong>\u00a0do\u00a0g\u00e1s<\/strong>\u00a0e \u00e9 dada pela equa\u00e7\u00e3o:<\/p>\n

K\u00a0m\u00e9d<\/sub>\u00a0= 3\/2 kT.<\/em><\/strong><\/p>\n

A energia interna de n moles de um g\u00e1s monat\u00f4mico ideal (um \u00e1tomo por mol\u00e9cula) \u00e9 igual \u00e0 energia cin\u00e9tica m\u00e9dia por mol\u00e9cula vezes o n\u00famero total de mol\u00e9culas, N:<\/p>\n

E\u00a0int<\/sub>\u00a0= 3\/2 NkT = 3\/2 nRT<\/em><\/p>\n

onde n \u00e9 o n\u00famero de moles.\u00a0Cada dire\u00e7\u00e3o<\/strong>\u00a0(x, ye z) contribui\u00a0(1\/2) nRT<\/em>\u00a0<\/strong>para a\u00a0energia interna<\/strong>\u00a0.\u00a0\u00c9 aqui que\u00a0entra a\u00a0id\u00e9ia<\/strong>\u00a0da\u00a0equiparti\u00e7\u00e3o de energia<\/strong>\u00a0– qualquer outra contribui\u00e7\u00e3o para a energia tamb\u00e9m deve contribuir\u00a0(1\/2) nRT<\/em><\/strong>\u00a0.\u00a0Como pode ser visto, a energia interna de um g\u00e1s ideal\u00a0depende apenas da temperatura<\/strong>\u00a0e do n\u00famero de mols de g\u00e1s.<\/p>\n<\/div>\n<\/div>\n

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Mol\u00e9cula Diat\u00f4mica – Energia Interna<\/h2>\n

Se as mol\u00e9culas de g\u00e1s cont\u00eam mais de um \u00e1tomo, existem\u00a0tr\u00eas dire\u00e7\u00f5es de transla\u00e7\u00e3o<\/strong>\u00a0e\u00a0a energia cin\u00e9tica rotacional<\/strong>\u00a0tamb\u00e9m contribui, mas apenas para rota\u00e7\u00f5es em torno de dois dos tr\u00eas eixos perpendiculares.\u00a0As cinco contribui\u00e7\u00f5es para a energia (cinco graus de liberdade) fornecem:<\/p>\n

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G\u00e1s ideal diat\u00f4mico:<\/span><\/strong><\/p>\n

E\u00a0<\/span>int<\/span><\/sub>\u00a0= 5\/2 NkT = 5\/2 nRT<\/span><\/em><\/p>\n

Esta \u00e9 apenas uma aproxima\u00e7\u00e3o e se aplica a temperaturas intermedi\u00e1rias.\u00a0<\/span>Em baixas temperaturas,<\/span><\/strong>\u00a0apenas a\u00a0<\/span>energia cin\u00e9tica translacional contribui<\/span><\/strong>\u00a0e, em temperaturas mais altas, duas contribui\u00e7\u00f5es adicionais (energia cin\u00e9tica e potencial) v\u00eam da vibra\u00e7\u00e3o.\u00a0A\u00a0<\/span>energia interna ser\u00e1 maior<\/span><\/strong>\u00a0a uma determinada temperatura do que para um g\u00e1s monat\u00f4mico, mas ainda ser\u00e1 uma fun\u00e7\u00e3o apenas da temperatura para um g\u00e1s ideal.<\/span><\/p>\n

A energia interna dos gases reais tamb\u00e9m depende principalmente da temperatura, mas, da mesma forma que a\u00a0<\/span>Lei do G\u00e1s Ideal<\/span><\/strong>\u00a0, a energia interna dos gases reais tamb\u00e9m depende um pouco da\u00a0<\/span>press\u00e3o<\/span><\/strong>\u00a0e do\u00a0<\/span>volume<\/span><\/strong>\u00a0.\u00a0Todos os gases reais se aproximam do estado ideal a baixas press\u00f5es (densidades).\u00a0A baixas press\u00f5es, as mol\u00e9culas est\u00e3o suficientemente afastadas para que n\u00e3o interajam.\u00a0A energia interna de l\u00edquidos e s\u00f3lidos \u00e9 bastante complicada, pois inclui\u00a0<\/span>energia potencial el\u00e9trica<\/span><\/strong>\u00a0associada \u00e0s for\u00e7as (ou\u00a0<\/span>liga\u00e7\u00f5es qu\u00edmicas<\/span><\/strong>\u00a0) entre \u00e1tomos e mol\u00e9culas.<\/span><\/p>\n<\/div>\n<\/div>\n

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Calor espec\u00edfico a volume constante e press\u00e3o constante<\/span><\/h2>\n

O calor espec\u00edfico<\/span><\/strong>\u00a0\u00e9 uma propriedade relacionada \u00e0\u00a0<\/span>energia interna<\/span><\/strong>\u00a0que \u00e9 muito importante na termodin\u00e2mica.\u00a0As\u00a0<\/span>propriedades intensivas\u00a0<\/span>c\u00a0<\/span>v<\/span><\/sub><\/em><\/strong>\u00a0e\u00a0<\/span>c\u00a0<\/span>p<\/span><\/sub><\/strong><\/em>\u00a0s\u00e3o definidas para subst\u00e2ncias compress\u00edveis puras e simples como derivados parciais da\u00a0<\/span>energia interna\u00a0<\/span>u (T, v)<\/span><\/em><\/strong>\u00a0e\u00a0<\/span>entalpia\u00a0<\/span>h (T, p)<\/span><\/em><\/strong>\u00a0, respectivamente:<\/span><\/p>\n

\"Calor<\/a><\/p>\n

onde os subscritos\u00a0<\/span>v<\/span><\/strong>\u00a0e\u00a0<\/span>p<\/span><\/strong>\u00a0denotam as vari\u00e1veis \u200b\u200bmantidas fixas durante a diferencia\u00e7\u00e3o.\u00a0As propriedades\u00a0<\/span>c\u00a0<\/span>v<\/span><\/sub>\u00a0<\/strong>e\u00a0<\/span>c\u00a0<\/span>p<\/span><\/sub><\/strong>\u00a0s\u00e3o referidos como\u00a0<\/span>calores espec\u00edficos<\/span><\/strong>\u00a0(ou\u00a0<\/span>capacidades de calor<\/span><\/strong>\u00a0), porque, sob determinadas condi\u00e7\u00f5es especiais dizem respeito a mudan\u00e7a de temperatura de um sistema para a quantidade de energia adicionada pela transfer\u00eancia de calor.\u00a0As suas unidades SI s\u00e3o\u00a0<\/span>J \/ kg K<\/span><\/strong>\u00a0ou\u00a0<\/span>J \/ mol K<\/span><\/strong>\u00a0.\u00a0Dois aquecimentos espec\u00edficos s\u00e3o definidos para gases, um para\u00a0<\/span>volume constante (c\u00a0<\/span>v<\/span><\/sub>\u00a0)<\/span><\/strong>\u00a0e outro para\u00a0<\/span>press\u00e3o constante (c\u00a0<\/span>p<\/span><\/sub>\u00a0)<\/span><\/strong>\u00a0.<\/span><\/p>\n

\"Calores<\/a>De acordo com a\u00a0<\/span>primeira lei da termodin\u00e2mica<\/span><\/strong>\u00a0, para processos de volume constante com um g\u00e1s ideal monat\u00f4mico, o calor molar espec\u00edfico ser\u00e1:<\/span><\/p>\n

C\u00a0<\/span>v<\/span><\/sub>\u00a0= 3 \/ 2R = 12,5 J \/ mol K<\/span><\/em><\/strong><\/p>\n

Porque<\/span><\/p>\n

U = 3 \/ 2nRT<\/span><\/em><\/strong><\/p>\n

Pode-se derivar que o\u00a0<\/span>calor molar espec\u00edfico<\/span><\/strong>\u00a0a press\u00e3o constante \u00e9:<\/span><\/p>\n

C\u00a0<\/span>p<\/span><\/sub>\u00a0= C\u00a0<\/span>v<\/span><\/sub>\u00a0+ R = 5 \/ 2R = 20,8 J \/ mol K<\/span><\/strong><\/em><\/p>\n

Este\u00a0<\/span>C\u00a0<\/span>p<\/span><\/sub><\/em><\/strong>\u00a0\u00e9 maior do que o calor espec\u00edfico molar a volume constante\u00a0<\/span>C\u00a0<\/span>v<\/span><\/sub><\/em><\/strong>\u00a0, porque a energia deve agora ser fornecidos\u00a0<\/span>n\u00e3o s\u00f3<\/span><\/strong>\u00a0para\u00a0<\/span>aumentar a temperatura<\/span><\/strong>\u00a0do g\u00e1s, mas tamb\u00e9m para o\u00a0<\/span>g\u00e1s de trabalho para fazer<\/span><\/strong>\u00a0porque neste volume caso altera\u00e7\u00f5es.<\/span><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

……………………………………………………………………………………………………………………………….<\/p>\n

Este artigo \u00e9 baseado na tradu\u00e7\u00e3o autom\u00e1tica do artigo original em ingl\u00eas. Para mais informa\u00e7\u00f5es, consulte o artigo em ingl\u00eas. Voc\u00ea pode nos ajudar. Se voc\u00ea deseja corrigir a tradu\u00e7\u00e3o, envie-a para: translations@nuclear-power.com ou preencha o formul\u00e1rio de tradu\u00e7\u00e3o on-line. Agradecemos sua ajuda, atualizaremos a tradu\u00e7\u00e3o o mais r\u00e1pido poss\u00edvel. Obrigado.<\/p>\n","protected":false},"excerpt":{"rendered":"

A energia interna \u00e9 o total de toda a energia associada ao movimento dos \u00e1tomos ou mol\u00e9culas no sistema e \u00e9 variada para gases monat\u00f4micos e mol\u00e9culas diat\u00f4micas.\u00a0Engenharia T\u00e9rmica Energia interna de um g\u00e1s ideal A\u00a0energia interna\u00a0\u00e9 o total de toda a energia associada ao movimento dos \u00e1tomos ou mol\u00e9culas no sistema.\u00a0As formas microsc\u00f3picas\u00a0de energia … Ler mais<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[14],"tags":[],"yoast_head":"\nO que \u00e9 energia interna do g\u00e1s ideal - g\u00e1s monat\u00f4mico, mol\u00e9cula diat\u00f4mica - defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"A energia interna \u00e9 o total de toda a energia associada ao movimento dos \u00e1tomos ou mol\u00e9culas no sistema e \u00e9 variada para gases monat\u00f4micos e mol\u00e9culas diat\u00f4micas. 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