{"id":2095,"date":"2016-03-28T23:13:34","date_gmt":"2016-03-28T23:13:34","guid":{"rendered":"http:\/\/fisicaevestibular.com.br\/novo\/?page_id=2095"},"modified":"2024-08-21T15:03:16","modified_gmt":"2024-08-21T15:03:16","slug":"tipos-de-transformacoes-gasosas","status":"publish","type":"page","link":"https:\/\/fisicaevestibular.com.br\/novo\/fisica-termica\/termodinamica\/tipos-de-transformacoes-gasosas\/","title":{"rendered":"Tipos de transforma\u00e7\u00f5es gasosas"},"content":{"rendered":"

Tipos de transforma\u00e7\u00f5es gasosas<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

O <\/b><\/span><\/span><\/span>estado de qualquer g\u00e1s<\/b><\/span><\/span><\/span> \u00e9 caracterizado pelos <\/b><\/span><\/span><\/span>valores de tr\u00eas grandezas que s\u00e3o o volume (V), a press\u00e3o (P) e a temperatura (T).<\/b><\/span><\/span><\/span><\/p>\n

S\u00e3o <\/b><\/span><\/span><\/span>muito comuns as transforma\u00e7\u00f5es em que ocorrem duas das vari\u00e1veis de estado, mantendo-se uma constante. <\/b><\/span><\/span><\/span>Pode-se ter, ent\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

Transforma\u00e7\u00e3o isot\u00e9rmica<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

Nela, <\/b><\/span><\/span><\/span>durante todo o processo termodin\u00e2mico de um g\u00e1s ideal,<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>temperatura permanece constante<\/b><\/span><\/span><\/span> (isso=igual; thermos = temperatura). <\/b><\/span><\/span><\/span><\/p>\n

O <\/b><\/span><\/span><\/span>cientista Robert Boyle comprovou que<\/b><\/span><\/span><\/span>, quando a <\/b><\/span><\/span><\/span>temperatura \u00e9 constante,<\/b><\/span><\/span><\/span> a <\/b><\/span><\/span><\/span>press\u00e3o (P) exercida por certa massa gasosa \u00e9 inversamente proporcional ao volume (V) por ela ocupado, <\/b><\/span><\/span><\/span>ou <\/b><\/span><\/span><\/span>P.V =<\/b><\/span><\/span><\/span> <\/b>constante,<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span>ou ainda, <\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>.V<\/b><\/span><\/span><\/span>o <\/b><\/span><\/span><\/sub><\/span>= P.V<\/b><\/span><\/span><\/span>.\u00a0<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

P<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0e V<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0representam a <\/b><\/span><\/span><\/span>press\u00e3o e o volume num estado de equil\u00edbrio inicial.<\/b><\/span><\/span><\/span><\/p>\n

P e V<\/b><\/span><\/span><\/span> representam a <\/b><\/span><\/span><\/span>press\u00e3o e o volume num estado de equil\u00edbrio final.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Isotermas<\/b><\/span><\/span><\/span><\/p>\n

Sendo <\/b><\/span><\/span><\/span>P.V = constante = k<\/b><\/span><\/span><\/span> \"\" <\/b><\/span><\/span><\/span>P =\"\" <\/b><\/span><\/span><\/span>e,\u00a0se <\/b><\/span><\/span><\/span>V tende a zero, P cresce indefinidamente<\/b><\/span><\/span><\/span> e\u00a0se <\/b><\/span><\/span><\/span>V cresce<\/b><\/span><\/span><\/span> <\/b>indefinidamente P tende a zero.<\/b><\/span><\/span><\/span><\/p>\n

Se voc\u00ea <\/b><\/span><\/span><\/span>representar graficamente P x V <\/b><\/span><\/span><\/span>voc\u00ea obter\u00e1 <\/b><\/span><\/span><\/span>uma <\/b><\/span><\/span><\/span>curva de nome<\/b><\/span><\/span><\/span>\u00a0isoterma<\/b><\/span><\/span><\/span>\u00a0que \u00e9 um\u00a0<\/b><\/span><\/span><\/span>ramo de uma hip\u00e9rbole eq\u00fcil\u00e1tera<\/b><\/span><\/span><\/span>.<\/b><\/span><\/span><\/span>\"\"<\/p>\n

Cada ponto da curva (isoterma) A tem a mesma temperatura (T<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>);<\/b><\/span><\/span><\/span> <\/b>cada ponto da curva (isoterma) B tem a mesma temperatura (T<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>) e cada ponto da curva (isoterma) C tem a mesma temperatura (T<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>).<\/b><\/span><\/span><\/span><\/p>\n

Observe que <\/b><\/span><\/span><\/span>T<\/b><\/span><\/span><\/span>C <\/b><\/span><\/span><\/sub><\/span>> T<\/b><\/span><\/span><\/span>B <\/b><\/span><\/span><\/sub><\/span>> T<\/b><\/span><\/span><\/span>A,<\/b><\/span><\/span><\/sub><\/span>\u00a0pois o produto P<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>V<\/b><\/span><\/span><\/span>A <\/b><\/span><\/span><\/sub><\/span>> P<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>V<\/b><\/span><\/span><\/span>B <\/b><\/span><\/span><\/sub><\/span>> P<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>V<\/b><\/span><\/span><\/span>C<\/b><\/span><\/span><\/sub><\/span>\u00a0e, assim <\/b><\/span><\/span><\/span>quanto mais afastada dos eixos maior ser\u00e1 o valor da temperatura da hip\u00e9rbole representativa.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span><\/p>\n

\u00a0<\/span><\/p>\n

Transforma\u00e7\u00e3o isoc\u00f3rica, isom\u00e9trica ou isovolum\u00e9trica<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

Nessa <\/b><\/span><\/span><\/span>transforma\u00e7\u00e3o o volume \u00e9 mantido constante<\/b><\/span><\/span><\/span> (isso=igual; coros=volume).<\/b><\/span><\/span><\/span><\/p>\n

Os f\u00edsicos <\/b><\/span><\/span><\/span>Jacques Charles e Gay-Lussac descobriram experimentalmente que<\/b><\/span><\/span><\/span>,\u00a0<\/b><\/span><\/span><\/span>numa <\/b><\/span><\/span><\/span>transforma\u00e7\u00e3o isoc\u00f3rica, a press\u00e3o (P) \u00e9 diretamente proporcional \u00e0 temperatura absoluta (T), <\/b><\/span><\/span><\/span>ou seja:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

A <\/b><\/span><\/span><\/span>express\u00e3o acima<\/b><\/span><\/span><\/span> s\u00f3 \u00e9 v\u00e1lida se considerarmos a <\/b><\/span><\/span><\/span>temperatura absoluta,<\/b><\/span><\/span><\/span> isto \u00e9, na <\/b><\/span><\/span><\/span>escala kelvin.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Se a <\/b><\/span><\/span><\/span>temperatura for medida em graus Celsius, isso n\u00e3o se aplica.<\/b><\/span><\/span><\/span><\/p>\n

Na express\u00e3o <\/b><\/span><\/span><\/span>P \/T<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span> = P\/T, conhecida como\u00a0<\/b><\/span><\/span><\/span>lei de Charles,<\/b><\/span><\/span><\/span>\u00a0P<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0e T<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sub><\/span>\u00a0representam a press\u00e3o e a<\/b><\/span><\/span><\/span> <\/b>temperatura absoluta do g\u00e1s no estado inicial:<\/b><\/span><\/span><\/span> <\/b>P e T representam, respectivamente, a press\u00e3o e a temperatura absoluta do g\u00e1s no estado final.<\/b><\/span><\/span><\/span>\u00a0<\/b><\/span><\/span><\/span><\/p>\n

Observe o <\/b><\/span><\/span><\/span>gr\u00e1fico abaixo onde voc\u00ea v\u00ea representada a lei de Charles<\/b><\/span><\/span><\/span> (transforma\u00e7\u00e3o isovolum\u00e9trica) que representa a <\/b><\/span><\/span><\/span>press\u00e3o (P) e a temperatura T, medida em graus kelvin (K) para 3 gases 1, 2 e 3.<\/b><\/span><\/span><\/span><\/p>\n

Como a temperatura <\/b><\/span><\/span><\/span>de um g\u00e1s perfeito diminui \u00e0 medida que a press\u00e3o tamb\u00e9m diminui, <\/b><\/span><\/span><\/span>ent\u00e3o <\/b><\/span><\/span><\/span>deveria existir uma temperatura muito baixa na qual a press\u00e3o seria <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

nula,<\/b><\/span><\/span><\/span> obtida pelo <\/b><\/span><\/span><\/span>prolongamento dos gr\u00e1ficos acima onde as retas representativas de cada g\u00e1s convergem para um<\/b><\/span><\/span><\/span> <\/b>\u00fanico ponto:<\/b><\/span><\/span><\/span> <\/b>-273,15<\/b><\/span><\/span><\/span>o<\/b><\/span><\/span><\/sup><\/span>C = 0 K,<\/b><\/span><\/span><\/span> no qual a <\/b><\/span><\/span><\/span>press\u00e3o exercida pelos gases torna-se nula.<\/b><\/span><\/span><\/span><\/p>\n

Na realidade, esse fen\u00f4meno n\u00e3o acontece,<\/b><\/span><\/span><\/span> pois \u00e9 <\/b><\/span><\/span><\/span>imposs\u00edvel se anular a press\u00e3o exercida por um<\/b><\/span><\/span><\/span> <\/b>g\u00e1s,<\/b><\/span><\/span><\/span> pois, com um <\/b><\/span><\/span><\/span>resfriamento suficiente, todos eles se liquefazem ou se solidificam.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span><\/p>\n

Transforma\u00e7\u00e3o isob\u00e1rica<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\u00a0Ocorre \u00e0 <\/b><\/span><\/span><\/span>press\u00e3o constante (isso=igual; baros=press\u00e3o).<\/b><\/span><\/span><\/span><\/p>\n

\u00a0O f\u00edsico <\/b><\/span><\/span><\/span>Jacques\u00a0<\/b><\/span><\/span><\/span>Charles<\/b><\/span><\/span><\/span>\u00a0observou que, para uma <\/b><\/span><\/span><\/span>certa massa de g\u00e1s perfeito, mantida a<\/b><\/span><\/span><\/span>press\u00e3o constante, o volume \u00e9 diretamente proporcional \u00e0 temperatura absoluta,<\/b><\/span><\/span><\/span>ou seja:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0A <\/b><\/span><\/span><\/span>rela\u00e7\u00e3o acima \u00e9 denominada lei de Charles e Gay-Lussac para transforma\u00e7\u00f5es isob\u00e1ricas<\/b><\/span><\/span><\/span> \u00a0e cujo <\/b><\/span><\/span><\/span>gr\u00e1fico V x T st\u00e1 representado abaixo:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Diagrama de Clapeyron para transforma\u00e7\u00f5es isob\u00e1ricas<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span><\/p>\n

Equa\u00e7\u00e3o de Clapeyron<\/b><\/span><\/span><\/span><\/p>\n

As <\/b><\/span><\/span><\/span>tr\u00eas leis anteriores<\/b><\/span><\/span><\/span> mostram como <\/b><\/span><\/span><\/span>um g\u00e1s perfeito se comporta quando mantemos uma vari\u00e1vel<\/b><\/span><\/span><\/span> <\/b>constante e variamos as outras duas.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

A <\/b><\/span><\/span><\/span>equa\u00e7\u00e3o de Clapeyron ou equa\u00e7\u00e3o de um g\u00e1s ideal<\/b><\/span><\/span><\/span> corresponde a uma <\/b><\/span><\/span><\/span>s\u00edntese dessas tr\u00eas leis,<\/b><\/span><\/span><\/span> que relacionam entre si <\/b><\/span><\/span><\/span>press\u00e3o, temperatura e volume.<\/b><\/span><\/span><\/span>
\nNuma <\/b><\/span><\/span><\/span>transforma\u00e7\u00e3o isot\u00e9rmica,<\/b><\/span><\/span><\/span> <\/b>press\u00e3o e volume s\u00e3o inversamente proporcionais<\/b><\/span><\/span><\/span> e em uma transforma\u00e7\u00e3o <\/b><\/span><\/span><\/span>isom\u00e9trica, isoc\u00f3rica ou isovolum\u00e9trica, press\u00e3o e temperatura s\u00e3o diretamente<\/b><\/span><\/span><\/span> <\/b>proporcionais.<\/b><\/span><\/span><\/span><\/p>\n

Pelas <\/b><\/span><\/span><\/span>informa\u00e7\u00f5es acima voc\u00ea pode concluir que a press\u00e3o \u00e9 diretamente proporcional \u00e0 temperatura e inversamente proporcional ao volume.
\n<\/b><\/span><\/span><\/span>Acontece que o <\/b><\/span><\/span><\/span>n\u00famero de mol\u00e9culas (n\u00famero de mols) influencia na press\u00e3o exercida pelo g\u00e1s,<\/b><\/span><\/span><\/span> ou seja, a <\/b><\/span><\/span><\/span>press\u00e3o tamb\u00e9m depende diretamente da massa do g\u00e1s<\/b><\/span><\/span><\/span> (n\u00famero de mol\u00e9culas nele contidas). <\/b><\/span><\/span><\/span><\/p>\n

Considerando esses resultados<\/b><\/span><\/span><\/span>, Paul Emile Clapeyron <\/b><\/span><\/span><\/span>estabeleceu uma <\/b><\/span><\/span><\/span>rela\u00e7\u00e3o entre as vari\u00e1veis de estado com a seguinte express\u00e3o matem\u00e1tica:<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Equa\u00e7\u00e3o geral dos gases perfeitos<\/b><\/span><\/span><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00c0 equa\u00e7\u00e3o acima se d\u00e1 o nome de lei geral dos gases perfeitos e voc\u00ea deve utiliza-la quando houver varia\u00e7\u00e3o de press\u00e3o, volume e temperatura simultaneamente, mantendo-se constante a massa.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

O que voc\u00ea deve saber, informa\u00e7\u00f5es e dicas<\/b><\/span><\/span><\/span><\/p>\n

\u00a0\"\"<\/span><\/p>\n

Transforma\u00e7\u00e3o Isot\u00e9rmica<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Isotermas<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span><\/p>\n

\"\"<\/p>\n

Transforma\u00e7\u00e3o isoc\u00f3rica, isom\u00e9trica ou isovolum\u00e9trica<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0\"\"<\/span><\/p>\n

Transforma\u00e7\u00e3o Isob\u00e1rica<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\u00a0<\/span><\/p>\n

Equa\u00e7\u00e3o de Clapeyron ou Equa\u00e7\u00e3o de um g\u00e1s ideal<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Nas <\/b><\/span><\/span><\/span>li\u00e7\u00f5es iniciais de um curso de mergulho com equipamento aut\u00f4nomo <\/b><\/span><\/span><\/span> \u2013 cilindro de ar <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

comprimido \u2013 os <\/b><\/span><\/span><\/span>alunos s\u00e3o instru\u00eddos a voltarem lentamente \u00e0 superf\u00edcie<\/b><\/span><\/span><\/span>, <\/b><\/span><\/span><\/span>sem prender sua<\/b><\/span><\/span><\/span> <\/b>respira\u00e7\u00e3o em hip\u00f3tese alguma,<\/b><\/span><\/span><\/span> a fim de permitir que <\/b><\/span><\/span><\/span>ocorra a gradativa descompress\u00e3o (diminui\u00e7\u00e3o da press\u00e3o).<\/b><\/span><\/span><\/span> <\/b><\/p>\n

O <\/b><\/span><\/span><\/span>aprisionamento do ar nos pulm\u00f5es pode ser fatal para o mergulhador durante a subida,<\/b><\/span><\/span><\/span> pois, nesse caso, a <\/b><\/span><\/span><\/span>transforma\u00e7\u00e3o sofrida pelo ar nos pulm\u00f5es \u00e9 isot\u00e9rmica, com aumento do volume do ar.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Como o <\/b><\/span><\/span><\/span>volume do cilindro que cont\u00e9m o g\u00e1s se dilata muito pouco<\/b><\/span><\/span><\/span> com a temperatura, pode-se dizer que se trata de uma <\/b><\/span><\/span><\/span>transforma\u00e7\u00e3o gasosa isom\u00e9trica ou isovolum\u00e9trica (volume constante)<\/b><\/span><\/span><\/span>. Como o carro <\/b><\/span><\/span><\/span>fica exposto ao sol, a temperatura do g\u00e1s aumenta e conseq\u00fcentemente a press\u00e3o<\/b><\/span><\/span><\/span> <\/b>exercida pelo g\u00e1s tamb\u00e9m aumenta, pois P\/T = constante e P \u00e9 diretamente proporcional a T, cujo<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

gr\u00e1fico PXT <\/b><\/span><\/span><\/span>est\u00e1 representado acima.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Um <\/b><\/span><\/span><\/span>bal\u00e3o de anivers\u00e1rio, cheio de g\u00e1s H\u00e9lio,<\/b><\/span><\/span><\/span> <\/b>solta-se da m\u00e3o de uma crian\u00e7a,<\/b><\/span><\/span><\/span> subindo <\/b><\/span><\/span><\/span>at\u00e9 grandes<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

altitudes e, devido a redu\u00e7\u00e3o da press\u00e3o, seu volume aumenta.<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Mistura de gases<\/b><\/span><\/span><\/span><\/p>\n

Considere dois <\/b><\/span><\/span><\/span>recipientes r\u00edgidos, de volumes V<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0e V<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0contendo, respectivamente, gases A e B. <\/b><\/span><\/span><\/span>Esses recipientes est\u00e3o <\/b><\/span><\/span><\/span>conectados entre si por um tubo fino munido de torneira que est\u00e1 fechada<\/b><\/span><\/span><\/span>. <\/b><\/span><\/span><\/span>Abre-se ent\u00e3o a torneira colocando os<\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

dois recipientes em comunica\u00e7\u00e3o, com os gases se misturando.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Ap\u00f3s a mistura, suas part\u00edculas ter\u00e3o o mesmo grau de agita\u00e7\u00e3o, portanto a mesma temperatura.<\/b><\/span><\/span><\/span><\/p>\n

Considerando <\/b><\/span><\/span><\/span>n o n\u00famero de mols da mistura, n<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0o n\u00famero de mols do g\u00e1s A e n<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0o n\u00famero de<\/b><\/span><\/span><\/span> <\/b>mols do g\u00e1s B, pode-se escrever<\/b><\/span><\/span><\/span>\u00a0 \"\"<\/b><\/span><\/span><\/span>\u00a0 n = n<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0+ n<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0 \"\"\u00a0 Clapeyron\u00a0 \"\" <\/b><\/span><\/span><\/span>PV = nRT<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 n = PV\/RT, que, <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

Se<\/b><\/span><\/span><\/span> P<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0for a press\u00e3o do no recipiente A antes da mistura e P<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>\u00a0a press\u00e3o no recipiente B antes da<\/b><\/span><\/span><\/span> <\/b>mistura,<\/b><\/span><\/span><\/span> tem-se\u00a0<\/b><\/span><\/span><\/span>P = P<\/b><\/span><\/span><\/span>A<\/b><\/span><\/span><\/sub><\/span>\u00a0+ P<\/b><\/span><\/span><\/span>B<\/b><\/span><\/span><\/sub><\/span>, onde <\/b><\/span><\/span><\/span>P \u00e9 a press\u00e3o total exercida pela mistura.<\/b><\/span><\/span><\/span><\/p>\n

\u00a0<\/span><\/p>\n

\"\"<\/p>\n

Veja um exerc\u00edcio interessante:<\/b><\/span><\/span><\/span><\/p>\n

Quando abrimos <\/b><\/span><\/span><\/span>uma geladeira com boa veda\u00e7\u00e3o<\/b><\/span><\/span><\/span> e <\/b><\/span><\/span><\/span>voltamos a fech\u00e1-la<\/b><\/span><\/span><\/span>, \u00e9 <\/b><\/span><\/span><\/span>dif\u00edcil abri-la <\/b><\/span><\/span><\/span>novamente em seguida.<\/b><\/span><\/span><\/span><\/p>\n

a) Como podemos <\/b><\/span><\/span><\/span>explicar esse fen\u00f4meno com base no comportamento termodin\u00e2mico dos gases?<\/b><\/span><\/span><\/span><\/p>\n

b) Considere uma <\/b><\/span><\/span><\/span>geladeira <\/b><\/span><\/span><\/span>com <\/b><\/span><\/span><\/span>volume interno de 1.000 L,<\/b><\/span><\/span><\/span> <\/b>temperatura<\/b><\/span><\/span><\/span> <\/b>interna -5\u00b0C e \u00e1rea da porta 2m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>.<\/b><\/span><\/span><\/span> Num dia <\/b><\/span><\/span><\/span>cuja temperatura ambiente \u00e9<\/b><\/span><\/span><\/span> <\/b>25\u00b0C, abrimos a porta da geladeira e a fechamos.<\/b><\/span><\/span><\/span> Supondo que todo <\/b><\/span><\/span><\/span>o ar frio no interior da geladeira seja substitu\u00eddo por ar \u00e0 temperatura ambiente, qual ser\u00e1 a for\u00e7a m\u00e9dia necess\u00e1ria para abrir a porta depois <\/b><\/span><\/span><\/span><\/p>\n

de <\/b><\/span><\/span><\/span>restabelecido o equil\u00edbrio termodin\u00e2mico no interior da geladeira?<\/b><\/span><\/span><\/span>\"\"<\/p>\n

(Dado: 1 atm \u2248 10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>\u00a0<\/b><\/span><\/span><\/span>N\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>).<\/b><\/span><\/span><\/span><\/p>\n

Resolu\u00e7\u00e3o:<\/b><\/span><\/span><\/span><\/p>\n

a) Se a <\/b><\/span><\/span><\/span>porta do freezer fica aberta por algum tempo, parte do ar de seu interior \u00e9 substitu\u00eddo pelo ar<\/b><\/span><\/span><\/span> <\/b>mais quente do exterior.<\/b><\/span><\/span><\/span> <\/b><\/p>\n

Depois que voc\u00ea <\/b><\/span><\/span><\/span>fecha a porta da geladeira, a temperatura interna do ar em seu interior ir\u00e1 diminuir<\/b><\/span><\/span><\/span> e como se trata de uma <\/b><\/span><\/span><\/span>isovolum\u00e9trica, a press\u00e3o tamb\u00e9m diminui (P\/T = constante) fazendo com <\/b><\/span><\/span><\/span><\/p>\n

\"\"<\/p>\n

b) Se a <\/b><\/span><\/span><\/span>press\u00e3o externa \u00e9 maior que a interna,<\/b><\/span><\/span><\/span> como <\/b><\/span><\/span><\/span>Press\u00e3o = For\u00e7a\/\u00c1rea da porta<\/b><\/span><\/span><\/span>, a <\/b><\/span><\/span><\/span>for\u00e7a externa<\/b><\/span><\/span><\/span> ter\u00e1 <\/b><\/span><\/span><\/span>intensidade maior que a for\u00e7a interna<\/b><\/span><\/span><\/span> e a intensidade da <\/b><\/span><\/span><\/span>for\u00e7a resultante ser\u00e1 F<\/b><\/span><\/span><\/span>R <\/b><\/span><\/span><\/sub><\/span>= F<\/b><\/span><\/span><\/span>ext<\/b><\/span><\/span><\/sub><\/span>\u00a0\u2013 F<\/b><\/span><\/span><\/span>int<\/b><\/span><\/span><\/sub><\/span>.<\/b><\/span><\/span><\/span><\/p>\n

A transforma\u00e7\u00e3o \u00e9 <\/b><\/span><\/span><\/span>isovolum\u00e9trica (volume constante)<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0<\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span>1<\/b><\/span><\/span><\/sub><\/span>\/T<\/b><\/span><\/span><\/span>1 <\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/T<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>1,0.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>x1.000 = P<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sub><\/span>\/(25 +<\/b><\/span><\/span><\/span> <\/b>273)<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 <\/b><\/span><\/span><\/span>P<\/b><\/span><\/span><\/span>2 <\/b><\/span><\/span><\/sub><\/span>= P<\/b><\/span><\/span><\/span>int <\/b><\/span><\/span><\/sub><\/span>= 0,9.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>N\/m<\/b><\/span><\/span><\/span>2<\/b><\/span><\/span><\/sup><\/span>\u00a0(P<\/b><\/span><\/span><\/span>a<\/b><\/span><\/span><\/sub><\/span>)<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0<\/b><\/span><\/span><\/span>\u0394<\/b><\/span><\/span><\/span><\/span>P = F<\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/sub><\/span>\/S<\/b><\/span><\/span><\/span>\u00a0 \"\"\u00a0 (1,0.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>\u00a0\u2013 0,9.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>) = F<\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/sub><\/span>\/2\u00a0 \"\"\u00a0 F<\/b><\/span><\/span><\/span>R <\/b><\/span><\/span><\/sub><\/span>= 0,2.10<\/b><\/span><\/span><\/span>5<\/b><\/span><\/span><\/sup><\/span>N\u00a0 \"\" <\/b><\/span><\/span><\/span>F<\/b><\/span><\/span><\/span>R<\/b><\/span><\/span><\/sub><\/span>=2,0.10<\/b><\/span><\/span><\/span>4 <\/b><\/span><\/span><\/sup><\/span>N.<\/b><\/span><\/span><\/span><\/p>\n

 <\/p>\n

Confira os exerc\u00edcios<\/span><\/a><\/h3>\n","protected":false},"excerpt":{"rendered":"

Tipos de transforma\u00e7\u00f5es gasosas \u00a0 O estado de qualquer g\u00e1s \u00e9 caracterizado pelos valores de tr\u00eas grandezas que s\u00e3o o volume (V), a press\u00e3o (P) e a temperatura (T). S\u00e3o muito comuns as transforma\u00e7\u00f5es em que ocorrem duas das vari\u00e1veis de estado, mantendo-se uma constante. Pode-se ter, ent\u00e3o: Transforma\u00e7\u00e3o isot\u00e9rmica \u00a0 Nela, durante todo o processo termodin\u00e2mico de um g\u00e1s<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2067,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-2095","page","type-page","status-publish","hentry"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2095","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/comments?post=2095"}],"version-history":[{"count":2,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2095\/revisions"}],"predecessor-version":[{"id":2103,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2095\/revisions\/2103"}],"up":[{"embeddable":true,"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/pages\/2067"}],"wp:attachment":[{"href":"https:\/\/fisicaevestibular.com.br\/novo\/wp-json\/wp\/v2\/media?parent=2095"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}