Chapter 3-1(A) The second Law of thermodynamics(part 1)
北化《物理化学》教学课件(上册,白守礼版)
Physical Chemistry
Introduction
Chapter 1 The properties of gases
Chapter 2The first law of thermodynamics Chapter 3The second law of thermodynamics Chapter 4 The thermodynamics of mixtures Chapter 5Chemical equilibrium
Chapter 6Phase equilibrium
北京化工大学理学院白守礼网学天地（）免费提供，北
z化学反应中常伴有能量的吸收或放出，
①直接的:
①对先行课：
①及格水平：
教材：
主要参考书：
物理化学
了解对比状态方程及其它真实气体方程
宏观定义：
z两个状态间的计算的例子
1．用物质量的分数表示:
1．分压定义
道尔顿分压定律只适用于低压气体或理想气体
1．分体积定义
压缩因子定义：
z范德华采用硬球模型来处理实际气体：
对理想气体
实际过程
g-l g
l
P
C
V
C
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一、实际气体在P ～Vm图上的等温线
1. T>t
气体可液化的最高温度——两段光滑曲
叫临界温度是是否可以液化的分解温度
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大学物理学第7章气体动理论(Temperature)
4
研究对象：大量无规则热运动气体分子构成的系统 研究内容：物质与冷热有关的性质及这些性质的变化
对象特点：单个分子 无序性、偶然性、遵循力学规律 整体（大量分子）：服从统计规律
mvx
l2
立直角坐标系。
a
O
-mvx
X
（2）选任意一个分子a作为研
究对象，求其对A1面的压力 Z
l1
分子“a” 的速度：
分子“ a”碰撞器壁A1面一次所受的冲量：
由牛顿第三定律可知，器壁A1面受分子碰撞一次所受的冲量：
23
分子“ a”相继碰撞器壁A1面两次所用的时间为： 单位时间内，分子“ a”与器壁A1面碰撞的次数为： 单位时间内，分子“ a”对器壁A1面的冲量即冲力为：
如压强 p、体积 V、温度 T等 .
平衡态：一定量的气体，在不受外界的影响下, 经过一 定的时间, 系统达到一个稳定的, 宏观性质不随时间变 化的状态称为平衡态 .（理想状态）
平衡态的特点
( p,V ,T )
p
*( p,V ,T )
o
V
1）单一性（
处处相等）;
2）物态的稳定性---与时间无关；
3）自发过程的终点；
（2）在平衡态下，分子按位置的分布是均匀的 n dN N
则各处分子数密度是相同的。
dV V
(3) 分子速度指向任何方向的机会是一样， 或分子速度按方向的分布是均匀的。
vx2 vy2 vz2
各个方向的速度分量的平均值相等。
vx 2
v1 x 2
ch3_The Second Law_Concepts Atkins Physical Chemistry (南阿拉巴马大学)
➢ Definition dS dqrev T
For measurable change DS 2 dqrev 1T
» Units of entropy: JK-1
Molar entropy: JK-1 mol-1
➢ Entropy change of isothermal expansion of an ideal gas
&
4
(rev.
adiabat),V
Tc
final f
Vinitial
T
c f
c
Cv,m
/
R
soVAThc VDTcc and VCTcc VBThc
combining by multiplication
VAVCTccThc VDVBThcTccorVAVC VDVB VA VD VB VC This means
Cold Reservoir
Heat
» If e, the efficiency of a heat engine is defined as |w|/qh, where qh is the temperature of the hot reservoir, the ultimate goal was to get e=1
➢ From the definition of entropy,
dSsur= dqsur /Tsur
{Note: dq can be reversible or not, see above}
And for a measurable change
DSsur= qsur /Tsur because Tsur is constant » For adiabatic change, qsur = 0, so DSsur = 0
西工大冯青版工程热力学课件第4章 热力学第二定律(新)
C Q1 A Q2
2
Q1
1C 2
Tds 面积1C2341
循环净放热量
Q0 Q1 Q2
1C 2
Tds Tds
1 A2
Tds
1 A 2C1
1
=面积1C2341-面积1A234=面积1A2C1
S 特点： Q0 逆时针循环，从低温吸热，向高温放热，向外界净放出热量 18
高温热 源
Q1
W0
Q2
低温 冷源
“代价”——吸热量 Q1 （注意不是 Q0 ！） 经济性指标热效率为
t
W0 Q1 Q2 Q 1 2 100% Q1 Q1 Q1
16
Chapter 4
The second law of thermodynamics
§４-２ 热力循环（Thermodynamic cycle)
1C 2
C
pdV
1A2
pdV
1 A 2C1
pdV
A
=面积1C234-面积1A234=面积1A2C1
2
特点： 逆时针循环，从外净输入循环功 W0
4
3
v
19
Chapter 4
The second law of thermodynamics
§４-２ 热力循环（Thermodynamic cycle)
§４-２ 热力循环（Thermodynamic cycle)
2.热力循环的分类（Classification of the Cycles） 按循环的效果不同，热力循环可分为正向循环和逆向循环。 正向循环就是在循环中把热能转变为机械能的循环，所 有的热力发动机（如汽车、船舶、航空动力装置）和其 它输出动力的装置（如蒸汽动力等）都是采用的这一循 环，故也称为动力循环(power cycle )或热机循环(thermal engine cycle ) 。 逆向循环就是在循环中把机械能转变为热能的循环，所 有的制冷机（如冰箱、空调等）和其它输出热能的装置 （如热泵等）都是采用的这一循环，故也称为制冷循环 (refrigeration cycle )或热泵循环(heat pump cycle )。
热力学第二定律与熵
dQ Sb S a a可逆 T
b
(dQ)可逆 TdS (dQ)可逆 或dS T
代入热力学第一定律表 达式： TdS dU pdV
这是综合了热力学第一、第二定律的热力学基本关系式。
熵的单位是：J.K-1
23
熵的定义：
若系统的状态经历一可逆微小变化，它与恒温 热源 T 交换的热量为 dQ ，则系统的熵改变了
2
功热转换:
功能自发且完全地转化为热, 但热不能自发且完全地转 化为功; 刹车摩擦生热。
热
气体自由膨胀:
气体体积能自发地由体积V1自由膨胀到体积V1＋V2；但不 能自发地由体积V1＋V2收缩为体积V1;
气体的混合:
气体A和B能自发地混合成混合气体AB，但不能自发地 分离成气体A和B.
热力学第二定律就是阐明热力学过程进行的方向。它决定 实际过程能否发生以及沿什么方向进行，也是自然界的一 条基本规律。 3
1
• 冰淇淋融化 • 冰冻的罐头变热
热传导（heat conduction）: Heat flows spontaneously from a substance at a higher temperature to a substance at a lower temperature and does not flow spontaneously in the reverse direction.
a
当联合机进行一次联合循环时，虽然外界没有
从 对它作功，而联合热机却把热量 Q2 Q2 Q1 Q1 低温热源传到高温热源，违反了克劳修斯的表述。
假定的
a可
b任
是错误的。
16
热力学第二、第三定律 英文版
• Recall, entropy is a state function; therefore, the entropy change for a chemical reaction can be calculated as follows:
DSo reaction
So prod
.
So react.
Sb4O6(s) + 6C(s)
What is DSsurr?
4Sb(s) + 6CO2(g) DH = 778 kJ
DSsurr = -DH/T = -778 kJ/298K = -2.6 kJ/K
The Third Law
• Recall, in determining enthalpies we had standard state values to use. Does the same thing exist for entropy?
• We need to know DS for both the system and surroundings to predict if a reaction will be spontaneous!
The Second Law (cont.)
• Consider a reaction driven by heat flow from the surroundings at constant P.
• The third law: The entropy of a perfect crystal at 0K is zference state for use in calculating absolute entropies.
– Exothermic Process: DSsurr = heat/T – Endothermic Process: DSsurr = -heat/T
第4章 热力学第二定律
1
T
q1
2
T1
q= 0 T2
3
1
2
q= 0
4
4
3
q2
0
v
0
Δs
s
3. The Efficiency of a Carnot Engine（卡诺热效率）
For any heat engine wnet q 1q 2 q2 t 1 q1 q1 q1 For a Carnot engine Method 1: From T-s diagram
T
a 2 1
q1-q2=wnet
b
0
p
1
4
3s
q w
qnet q1 q2 wnet
a
wnet
b 2
Q W
Qnet Q1 Q2 Wnet
0
4
3 v
（3）The coefficient of performance（工作系数） The COP of a refrigerator
（2）p-v and T-s diagrams
p-v diagram
p
1 a
counterclockwise direction • 1-b-2: expansion • 2-a-1: compression
0
4
wnet
b 2
3 v
T-s diagram counterclockwise direction • 1-b-2: absorb heat • 2-a-1: reject heat Cycle
（4）Mixing（混合过程）
Gas
evacuated
Gas A
专业英语
1.热力学第一定律：the first law of thermodynamicsA :It was stated for a cycle :the net heat transfer is equal to the net work done for a system undergoing a cycle2.热力学第二定律:the second law of thermodynamicsIt is impossible to construct a device that operates in a cycle and whose sole effect is the transfer of heat from a cooler body to a hotter bodyIt is impossible to construct a device that operates in a cycle and produces no other effect than the production of work and the transfer of heat from a single body3.传热学与热力学区别A :heat transfer is the science that seeks to predict the energy transfer that may take place between material bodies as a result of a temperature difference .Thermodynamics teaches that this energy transfer is defined as heat .The science of heat transfer seeks not merely to explain how heat energy may be transferred but also predict the rate at which the exchange will take place under certain specified conditionsThere are three modes of heat transfer1)Conduction heat transfer 2 Convection heat transfer 3 Radiation heat transfer4.锅炉boiler Boilers use heat to convert water into steam for a variety of applications5.热电厂thermal power plantA power station operates using a closed steam power cycle ,where water undergoes various thermodynamic processes in a cyclic process.6.空调air conditioningAir conditioning is a combined process that performs many functions simultaneously .It conditions the air ,transports it and introduces it into the conditioned space ,it also controls and maintains the temperature humidity ,air movement ,air cleanliness .7.制冷原理refrigerationRefrigeration is defined as the process of extracting heat from a lower temperature heat source substance or cooling medium and transferring it to higher temperature heat sink it contains four process ,corresponding four parts .Condenser --expansion valve --evaporator --compressor冰箱的作用：cold storage and preservation二：主关件简介：：压缩机一：Compressor 制冷系统的“心脏”起压缩和输送制冷剂的作用，制冷系统的“心脏”起压缩和输送制冷剂的作用，目前所用为往复活塞式压，缩机。
厦门大学-化学热力学的体系和状态
热力学第二定律
二.混乱度（ disorder）和熵（entropy）
从微观分析上述例子，可以得出共同结论：自发过程 是从有序到无序，从无序变为更加无序，条件是：外界不给 体系以热或作功就可以看作孤立体系，因为在外力作用下， 可以使混乱度大的状态变成有序状态。
热化学
2.在298K、1 atm下，化学反应的热焓变化∆H称 为标准反应热焓，r用om 表示
3.生成焓与化学反应的反应热之间的关系:
r o m vif o m ,i(产) 物vjf o m ,j(反应 ) 物
r
o m
,1
r
o m
,
2
例1 例2
r
o m ,3
r
o m
,2
+
r
o m
,1
=
r
o m ,3
四.热焓(enthalpy) 1.定义: HUpV 2.在恒压条件下的反应热等于焓变. 3.∆H与∆U的关系:
(1) Tconsntancot,nst aΔnU t0,ΔΔ(p0 VH0 (2) Δn0,pV nRT(cTons)tant
ΔH ΔU Δp VΔU ΔnRT
例 U： 2 28 9在 Kk5 8时 g0m ， 1， oB 反 l4求 C 应 (s4)O2 2B 2O3CO 2(g的 ) 解： n143,HUnRT28k2g7m 1 ol
(2)在化学中规定： 体系对环境作功为+，体系吸热为+，
环境对体系作功为-，体系放热为-.
一出一进为正一 进一出为负
它们在热量上符号一致，但在功的符号上相反 我们只使用化学上的符号规定.
热力学第一定律
热力学定律英文版
热力学定律英文版Thermodynamics is a branch of physics that deals with the study of the relationships between heat, energy, and work. It is a well-established and widely applicable field of study that iscritical to the development of modern engineering and technology. One of the key concepts in thermodynamics is the set of laws that govern the behavior of thermal systems. There are four main thermodynamic laws, each of which contributes to our understanding of thermodynamics in different ways. In this article, we will discuss these laws and their applications in detail.The first law of thermodynamics is also known as the law of conservation of energy. It statesthat energy cannot be created or destroyed, only converted from one form to another. This law is important because it helps us understand how energy flows through a system. In essence, it tells usthat there is a fixed amount of energy in a system, and that energy can be transformed from one form to another. This law has wide-ranging applications infields such as engineering, where it is used to design heat engines and other thermal systems.The second law of thermodynamics deals with entropy. Entropy is a measure of the disorder or randomness of a system. The second law states that entropy always increases over time, which meansthat as time goes by, systems tend to become more disordered. This law is important because it helps us understand why some processes are irreversible. For example, if you mix hot and cold water in a glass, the heat will eventually dissipate and the water will reach equilibrium. This process cannot be reversed because it would require the heat to flow from the cold water back to the hot water, which violates the second law of thermodynamics.The third law of thermodynamics deals with the behavior of matter as it approaches absolute zero. Absolute zero is the lowest temperature possible, and under these conditions, matter behaves differently than it does at higher temperatures. The third law states that it is impossible to reach absolute zero through any finite number of steps.This law has applications in the study of superconductivity and other unusual phenomena that occur at very low temperatures.The fourth law of thermodynamics is a theoretical construct that deals with the behavior of systems that are far from equilibrium. It states that in such systems, there is a tendency for order to emerge spontaneously. This law is still being explored and studied, and its exact implications are not yet fully understood.In conclusion, the laws of thermodynamics play a critical role in our understanding of energy and heat flow in physical systems. These laws have a wide range of applications in engineering, physics, chemistry, and other fields, and they are constantly being refined and expanded as new discoveries are made. By studying thermodynamics, we can gain a greater appreciation for the complex interplay between energy, matter, and the forces that govern our universe.。
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Chapter 3 The Second Law of Thermodynamics
3.1 Spontaneous process and its characteristic
That First law of thermodynamics, however, can’t tell us the direction of those permissible changes. The processes which happen in the nature are all obedient to the First law, but all processes in which energy is conserved can’t occur. For example: ① ② ③ ④ ⑤ work heat 100% potential energy heat Q high temperature object diffusion process Zn+CuSO4→Cu+ZnSO4
Chapter 3 The Second Law of Thermodynamics
3.2 The Second Law of Thermodynamics
⑤热力学第二定律原则上可用来判断任何一过程进行的方 向问题，但实际上对每一过程根据“第二类永动机不可能 造成”这一结论来判断过程的方向，这就太抽象，太繁了。 再说，这一判断方法并不能指出过程进行到什么程度为止。 因此，最好能像第一定律，找出像内能Ｕ 和焓Ｈ 那样的热 力学函数，只需计算ΔＵ和ΔＨ 就可知道－过程的能量变化 那样，在第二定律中，是否就可以找到这样的热力学函数， 只要计算此函数的变化值，就可判断过程的方向和限度呢？ 由于一切自发过程的方向性最后都可归结为热功转化 问题，故所要寻找的热力学函数亦得从热功转化的关系中 去找。这就是下面要讲的内容。
The ⑥,⑦,⑧,⑨and⑩ processes mentioned above follows the First law of thermodynamics, but none of these processes happens spontaneously.
Chapter 3 The Second Law of Thermodynamics
100%
low temperature object
Chapter 3 The Second Law of Thermodynamics
3.1 Spontaneous process and its characteristic
But 100% ⑥heat work ? Q ⑦low temperature object high temperature object ? ari sin g ⑧heating an object potential energy？ ⑨Can the reversible process of diffusion process occur? ⑩Cu+ZnSO4→Zn+CuSO4?
Chapter 3 The Second Law of Thermodynamics
3.1 Spontaneous process and its characteristic
The First law of thermodynamics led to introduction of the internal energy, U, and states： That energy is conserved in any process. That is, the total energy of an isolated system is constant. ΔU=Q+W. The kind of energy exchange between the system and surroundings, heat and work, and the quantitative relation between them. That let us assess whether a change is permissible : only those changes many occurs for which the internal energy of an isolated system remains constant.
Chapter 3 The Second Law of Thermodynamics
3.2 The Second Law of Thermodynamics
① 讨论： Clausius 说法中，要注意“不引起其它变化”。 热是可以从低温物体传到高温物体。例：冰箱，空调， 但会引起其它变化（功→热）。 ② Kelvin说法中同样要注意“不发生其它变化”。因为 理想气体的恒温膨胀是（Q=-W）吸热全部用来做功。但引 起状态变化。 ③Clausius 说法和Kelvin说法是等价的。 ④第二类永动机并不违背热力学第一定律，也就是说，第 一定律只能解决能量守恒问题而不能指出能量传递的方向， 要解决方向问题需要第二定律。如果第二类永动机能存在， 其功效不亚于第一类永动机。因为人们航海可不带燃料， 将大海作为第一热源即可。
Chapter 3 The Second Law of Thermodynamics
不可能把热从低温物体传 到高温物体，而不引起其 它变化
上一内容
下一内容Biblioteka 回主目录返回Chapter 3 The Second Law of Thermodynamics
♣2.1 Spontaneous process and its characteristic ♣2.2 The second law of thermodynamics ♣2.3 Carnot cycle ♣2.4 Entropy and the entropy growth principle ♣2.5 Calculating the entropy change for the process of single (simple) pVT change ♣2.6 The entropy of phase transition ♣2.7 The third law of thermodynamics and the calculation of entropy change for chemical reaction ♣2.8 The Helmholtz energy (function) and Gibbs free energy (function) ♣2.9 The fundamental equations of thermodynamics ♣2.10 The clapeyron equation ♣2.11 The Gibbs——Helmholtz equation and The Maxwell relations
Chapter 3 The Second Law of Thermodynamics
3.2 The Second Law of Thermodynamics
3.2 The second law of thermodynamics 自发过程的共同特点是其热力学上不可逆性（注意： 非自发过程不是不能发生的，而是要借助外力）。这种 不可逆性最终都可归结为“ 热能是否全部转化为功而不 引起任何其它变化”这样基本一个问题。 例如：Zn+CuSO4→Cu+ZnSO4+Q 反应是自发进行的。 要想系统恢复原状，需对系统作电功进行电解 。 Cu+ZnSO4 → Zn+CuSO4+Q' W，-Q' 如果电解时所做电功为W，同时有 Q ' 的热放出，那 么，当反应系统恢复原状时，环境损失功W。 得到热 Q + Q ' 。 根据第一定律 W= Q + Q '
3.1 Spontaneous process and its characteristic
What is Spontaneous process (or change)? The process which happens naturally in the nature is called spontaneous process. What is Spontaneous characteristic? The characteristics of spontaneous process is its irreversibility. Any spontaneous process is irreversible. Work can be done by making use of spontaneous process. For example, hydroelectricity and chemical energy cell electrical energy are instances of making use of spontaneous processes.
Chapter 3 The Second Law of Thermodynamics
3.3 Carnot cycle
1824 年，法国工程师 N.L.S.Carnot (1796~1832)设 计了一个循环，以理想气体 为工作物质，从高温 (Th ) 热源 吸收Qh 的热量，一部分通过 理想热机用来对外做功W，另 一部分 Qc 的热量放给低温 (Tc ) 热源。这种循环称为卡诺循 环。
Chapter 3 The Second Law of Thermodynamics
3.2 The Second Law of Thermodynamics
克劳修斯（Clausius）的说法：“不可能把热从低温物体 传到高温物体，而不引起其它变化。”
开尔文（Kelvin）的说法：“不可能从单一热源取出热使 之完全变为功，而不发生其它的变化。” 后来被奥斯特 瓦德(Ostward)表述为：“第二类永动机是不可能造成 的”。 第二类永动机：从单一热源吸热使之完全变为功 而不留下任何影响。