Unit 7 Physical Chemistry
Physical chemistry is the study of the physical basis of chemical systems and processes. Modern physical chemistry is firmly grounded upon physica. Important areas of study include chemical thermodynamics, chemical kinetics, quantum chemistry, statistical mechanics, electrochemistry, surface and solid state chemistry, and spectroscopy.
物理化学是对化学系统和过程的物理基础的研究。现代物理化学以物理为基础。重要的研究领域包括化学热力学、化学动力学、量子化学、统计力学、电化学、表面和固体化学以及光谱学。
We have repeatedly referred to the energy effects accompanying chemical and physical changes. Thermodynamics is the study of these energy effects in particular, it summarizes the relations between heat, work, and other forms of energy that are involved in all types of changes. The laws of thermodynamics can be used to predict whether a particular chemical or physical transformation is theoretically possible under a given set of conditions. Furthermore, if a study shows that a desired change will not occur under the conditions assumed, thermodynamic principles can be used to determine how the conditions can be altered to make the change theoretically possible.
我们一再提到伴随着化学和物理变化的能量效应。热力学是对这些能量效应的研究，特别是，它总结了热、功和其他形式的能量之间的关系，这些关系涉及到所有类型的变化。热力学定律可以用来预测在给定的一组条件下，一种特定的化学或物理转化是否在理论上是可能的。此外，如果研究表明在假定的条件下不会发生期望的变化，则可以用热力学原理来确定如何改变条件，使这种变化在理论上成为可能。
Lesson 22 First Law of Thermodynamics
Thermodynamics had its origin in the investigation of the relation between mechanical work and heat. Many scientists of the late eighteenth and early nineteenth conversion of mechanical work into heat. However, the careful and convincing studies of James Joule, in the years 1840 to 1849. firmly established the principle that work could be converted into heat and provided a quantitative value for the mechanical equivalent of heat.
热力学起源于对机械功与热关系的研究。许多科学家在十八世纪末和十九世纪初将机械功转化为热能。然而，詹姆斯·朱尔在1840年至1849年的仔细和令人信服的研究。它坚定地确立了功可以转化为热的原理，并为热的机械当量提供了一个定量的值。
Joule studied the conversion of work into heat in many ways. He used the work done by a falling weight to turn a paddle wheel immersed in a container of water and determined the heat produced by measuring the increase in temperature of the water. In a series of such experiments, he used different weights and different quantities of water, as well as mercury in place of the water. Joule also studied the heating effects of electric currents and the conversion of work into heat by the compression of gases. In all his experiments, Joule found that a given amount of work produces adefinite quantity of heat. In modern terms, the relation is
焦耳从许多方面研究了功转化为热的问题。他用下降的重量所做的工作来转动浸入水的容器中的桨轮，并测量水的温度升高所产生的热量。在一系列这样的实验中，他用不同的重
量和不同数量的水以及水银代替了水。Joule还研究了电流的加热效应以及通过压缩气体将功转化为热的过程。在他的所有实验中，Joule发现，给定的工作量会产生一定数量的热量。在现代意义上，这种关系是
4.1840J=1cal
One joule, the unit of work, is 107 ergs, and 1 erg is the work done when a force of Dyne (or Ig cm/sec) acts through a distance of lcm. The calorie, which was originally defined as the amount of heat required to raise the temperature of Ig of water from 14.5 to 15.5'C, is now defined by its joule equivalent.
一焦耳，单位的功，是107 ergs，1 erg是当dyne(或Ig cm/sec)的力作用于LCM的距离时所做的功。热量最初被定义为将水的Ig温度从14.5℃提高到15.5‘C所需的热量，现在用其焦耳当量来定义。
The recognition that heat and work are quantitatively related led to the concept that they are manifestations of a larger classification, energy, which is conserved. The first law of thermodynamics, which is the law of conservation of energy, states that energy can be converted rom one form into another but cannot be created or destroyed.
人们认识到热和功是定量联系在一起的，这就产生了这样的概念：热量是一种更大的分类的表现形式，能量是保守的。热力学第一定律是能量守恒定律，它指出能量可以转化为另一种形式，但不能被创造或破坏。
In applying thermodynamic concepts, we frequently confine our attention to the changes that occur within definite boundaries. That portion of the universe included within these boundaries is called a system; the remainder of the universe is called the surroundings. If there is no exchange of mass between a system and its surroundings, the
system is spoken of as a closed system. In addition, energy is not exchanged between the system and its surroundings, the system is referred to as an isolated system. Work done on a system need not always result in an increase in the temperature of the system or the conversion of work into heat. For example, the charging of a storage battery by an automobile engine results in an increase of the chemical energy, of the batter: doing work on (or adding heat to) a sample of ice at 0 could result in melting a part of the ice with no increase in the temperature of the system. A system is assumed to have an internal energy, Q which includes all possible forms of energy attributable to the system.
在应用热力学概念时，我们经常将注意力局限于在一定边界内发生的变化。包括在这些边界中的宇宙的那一部分被称为一个系统；宇宙的其余部分被称为环境。如果一个系统和它的周围没有质量交换，那么这个系统就是一个封闭的系统。此外，系统与周围环境之间不进行能量交换，系统被称为孤立系统。在系统上所做的工作不一定总是导致系统温度的升高或功转化为热。例如，汽车发动机对蓄电池充电会增加面糊的化学能量：在0?时对一个冰样品进行工作(或向其添加热量)可能导致部分冰的融化，而不增加系统的温度。假设一个系统有一个内部能量，Q包括可归于该系统的所有可能形式的能量。
According to the first law of thermodynamics, the internal energy of an isolated system is constant. The actual value of E for any system is not known, nor can it be determined. However thermodynamics is concerned only with changes in internal energy, and such changes are measurable.
. 根据热力学第一定律，孤立体系的内能为常数。对于任何系统，E的实际值都是未知的，也不能确定。然而，热力学只关注内部能量的变化，这种变化是可以测量的。
The internal energy of a system depends upon the state of the system and not upon
how the system arrived at that state. Internal energy is therefore called a state function. Consider a sample of an ideal gas that occupies a volume of 1 liter at 100K and 1atm pressure (state A). At 200K and 0.5atm (state B), the sample occupies a volume of 4 liters. According to the first law, the internal energy of the system in state A, EA, is a constant, as is the internal energy of the system in state B EB. It follows that the difference in the internal energies of the two states. A is also a constant and is independent of the path taken between state A and state B. It makes no difference whether the gas is first heated and then the pressure changed, whether the heating is done after the pressure change, or indeed whether the total change is brought about in several steps.
系统的内部能量取决于系统的状态，而不是系统如何到达该状态。因此，内部能量被称为状态函数。考虑一个理想气体的样本，在100 K和1 atm压力下，它的体积为1升(状态A)。在200 K和0.5atm(B状态)下，样品体积为4升。根据第一定律，系统在A，EA中的内能是一个常数，而在B状态EB中，系统的内能也是常数。因此，这两种状态的内部能量的差异。A也是常数，与A状态和B状态之间的路径无关。气体首先加热后压力变化，加热是在压力变化后进行，还是总变化是分几个步骤进行，两者没有关系。
If E were not independent of the manner in which the corresponding change was brought about, it would be possible to create or destroy energy, in violation of the first law, by taking a system from A to B by one route and then returning it to state A by a different route. Instead, in a cyclic process (in which a system is returned to its original state), the increase in B in one direction exactly equals the decrease in B in the opposite direction so that for the cycle there is no net gain or loss in energy.
如果 E 不独立于相应变化的产生方式，则有可能违反第一定律，通过一条路线将系