ʱ : 热力学第一定律基本概念和重点总结 - 百度文库ϿʼĶ
A?B?PлѧӦ
1.ձкѹӦ 2.кѹӦ
a. H1=H2 b. H1=QP,I c. H2=QP,2 ĸȷ
(heat capacity)
ӰݵҪ Ħ ѹĦ
Ħ¶ȱ仯ıʽ ʵļ һӰݵҪ 壺
һɲ䡢ʵһľϵ,Wf0£ÿߵλ¶յȳΪʵݣCʾ ƽݣ defQQ C = ?T2?T1?T
ݵλJK-1
ʵΪ1KgΪݣλΪJKKgʵΪ1molΪĦ(Ϊ)λΪJKmol
defC(T)
Cm(T) n1.ʵ״̬ ѹһʱ
C(Ҵ,l)Kmol C(ˮ,l)Kmol C(ˮ,g)Kmol
ͬC̬ͬͬͬCҲͬ 2. ¶ȷΧ
ʵ֤ͬһڲͬ¶ȷΧڣ¶ÿKͬˣ¶ T KʱӦʾΪ def?Q C(T) dT
ϵСյΪ
?Q?C(T)dT
¶T1 T2ʱ
T2
==Q??C(T)dTT1
3. ¹
Ϊ;;ͬȵֵֵͬҲͬڻоǵѹݹ̣ӦҲжѹݺͶ Ħ 壺
ɲľϵʵΪ1molʱڵݡWf0 ĹеΪĦݣ CVm ʾλΪ JKmol
CV(T)1?QV?UmC(T)??C(T)?()V V,mV,mnndT?T
?Um?CV,mdT
¶ڶ֮T1 T2ʱ
T2T2
?U?QV?n?Um?nCV,mdT?CVdTT1T1
ڴ¶䷶ΧڣCV,m ɿ
?U?QV?nCV,m(T2?T1)?CV(T2?T1)
(ϵݣWf0PVT仯) ѹĦ 壺
ɲľϵʵΪ1molʱڵѹWf 0ĹеΪѹĦݣCPm ʾλΪJKmol
?HmCp(T)1?QpC(T)?()P Cp,m(T)??p,m?TnndT
?Hm?CP,mdT
¶ȶ֮T1 T2ʱ
T2T2
?H?QP?n?Hm?nCp,mdT?CpdTT1T1
ڴ¶䷶ΧڣCP,m ɿ ?H?QP?nCP,m(T2?T1)?CP(T2?T1)
(ϵѹWf 0PVT仯 ) ˵
C Pm C Vm Ϊ״̬Ϊϵǿʡ ġĦ¶ȱ仯ıʽ ¶ȵĺϵʡ̬¶IJͬвͬʽϵʽ:
2 p,m(T) ''?1'?2C(T)?a?bT?cT????p,m
??????C?a?bT?cT????ʽ abcabc Ǿ鳣ɸʱԾɴѧݱвҡ һ㴿ʼɽϺ㶨Ļ磺C PmfTڻѧֲϲ鵽 ע⣺
ٲõCp,m Cp =nCp,m
ھ鳣һ¶÷ΧҲֵ̬ͬͬ
仯̣ȵӦֶνУҪȵֵ
ȱʵʱɷ˶ۿɶȾԭƹ㣺 ԭ C Vm C Pm ˫ԭ C Vm C Pm
Ͷԭ C Vm3R C Pm4R 塢ʵļ
仯һ£ʴһΪһĹ̳Ϊ仯.
ȣһں㶨¶ȼѹͨΪָ¶ȵƽѹ·ʱ뻷Ϊȡ
Ϊѹ̣Wf0ȿʱʾΪʡ
1molں㶨¶T¶ȵƽѹ·ʱӦʱΪʣԦHmʾΪJmol1kJmol1磺
̣vapHm ?̣subHm ۻ̣fusHm
glHm
?Hm ?Hm
lS
gS
ע⣺
ͬһʷͬһʵֵ뷢йأ
1molʽɦൽ䣬Ϊ ͬһɦൽʱΪ У ???H????m?Hm
ΪHfTpҲTpйأѹΪָ¶µƽѹpfTH䣽f(T) ѧһɶӦ
ѧܺ
CP,m CV,m֮ ȹ̵Ĺ̷ʽ
һѧܺʡGay-Lussac-Jouleʵ
Gay-Lussac1807꣬Joule1843ֱʵ飺
һͨһװ壬һգͨоȱڵˮԡУˮв¶ȼƣΪϵˮΪ
ֱƽΪֹ۲ˮޱ仯 ʵ
Q?0ˮԡ¶Ⱦδ䦤T = 0
ʵ鷢֣ʵԽӽ壬T = 0ĽԽȷ Ʋ⣺壬T = 0Ľ۾ȫȷ
W?0ϵͳûж
ѧһɣù̵ ?U?0˵ͺѧܲ
1. ѧ
ѧ T,V ĺ
??U???U?U?U(T,V) dU??dT????dV??T?V??V?T
Jouleʵ
dT?0, dU?0
??U? ??dV?0??V?T
??U?Ϊ ???0?V??T
ڵʱıѧܲ ѧT,P ĺ
??U? ???0U?U(T,p)?p??T ֤
壬Tһʱѹ仯Ҳѧֵı仯
ۣڵpVT仯̣䡢ѧӦܽΪ¶ȵĺѹ
U?U(T)
ҲΪJoule 2.
H?U?pVʵĶʽ
?H??U??(pV)??U??(nRT)
¹ ?U?0 ?T?0 Ҳ¶ȵĺѹ ֤ͬ
??H???H? ???0???0?V??T??p?T
H?H(T)
dV?0