The First Law 课堂版.ppt

1、The science which is concerned with heat and work, and transformations between the two.,thermodynamics,Every one has learned the physical chemistry and known about the three laws of thermodynamics What can I DO FOR YOU?,1)Make you be familiar with the English notion and definitions for the thermodyn

2、amic items 2)Recite the knowledge in a new way and make you like thermodynamics,the principle of conservation of energy; that is, energy can be neither created nor destroyed. dW+dQ is dU,The first law,A Sonnet to First Law,How could I have doubted your constancy your warmth and labors summed, signif

3、y your ever unchanging incessancy. Though some virtues wane, will others supply perfect completeness in my universe. Are we not a pair, born of heat and toil, controvertible, not better nor worse. Though shoulders may be cold or blood may boil, you are balanced and never violated. Timeless compass o

4、f perfect reckoning, northern star of mislaid paths translated, you, the first, though a second, beckoning Nature, forever, through her laws eschew dw + dq is dU,献给第一定律的十四行诗,怎能质疑你的可靠性 对热功描述的准确性 在变化环境下一致性 虽然规律不总是适用 你却适用我整个世界,热和功是天生的一对 这个说法却有待商榷 可是此处冷彼处就热 能量的守恒经久不变,时间给出了恰当评价 自然和我们做迷藏时 在第一时间就能瞬间 照亮了前程的

5、北极星 它就是 dw+dq=dU,Now lets get some items, which you meet very often, into in English. pay attention to the English definition for the items!,System and surrounding,system: any portion of space or matter set aside for study. Open system: both matter and energy exchanges are involved Closed system: en

6、ergy exchange with the surroundings is involved, but no matter exchange Isolated system: no matter or energy exchange with the surroundings is involved Surrounding: everything else, the universe outside the system,Open system: water Closed system: water+container Isolated system : water+ container +

7、 surrounding air,Water in a Closed Container,Open system: Closed system: Isolated system :,raw materials raw materials+air in the furnace raw materials+air in the furnace+surrounding,Metallurgy,Heat and work,energy transferred between system and surroundings is divided into two categories: Heat (Q):

8、 the energy changed because of the different temperatures Work (W) :all other forms of energy,Algebraic sign of heat and work:,Two ways to change the state of water,James P. Joule (1818-89), born in Salford, Lancashire worked in a brewery, painstakingly established the equivalence of heat and work,

9、hero of thermodynamics.,Reversible and irreversible possesses,whether the process of turning the initial state to the finial state is an infinite way, or not.,Reversible mechanical works,Names for the energy,Kinetic energy Potential energy Internal energy,mechanical energy (Elastic energy),Chemical

10、energy,electric and magnetic energy,surface energy,Thermal energy,the total energy of the particles in a system including the kinetic energy (thermal motion) of every particle, and the potential energy caused by the interaction between particles. The kinetic energy of the system by the movement in t

11、he macrocosm or the potential energy due to the position of a system in the macrocosm is not considered in this definition.,State and state function,State (macroscopic):the total of all properties Intensive and extensive properties State functions (convenience):variables independent and dependent va

12、riables,Intensive and extensive properties,Intensive properties: density (kg, g etc.) temperature (T), pressure (P), physical gathering state (gaseous, liquid, solid) chemical composition (Xi) Extensive properties: volume (V), energy U, enthalpy H, entropy S and free energy G and F,The main characte

13、r of state function： （1）when the state is fixed，the state function have a certain value； （2）the change of the state function is only relative to the start state and the end state but not the to process path,after a circle the change of state function is zero Euler equation:,Graduate Course, Nanchang

14、 University,Change of state is not dependent on the path but on the process ( the start point and the end point),Path and process,d is the differential of state function, is the differential of the thing that is not state function,Lesson Two,Enthalpy,The term U+PV is defined as enthalpy. The letter

15、“H” designates it. H U+PV Specific enthalpy is enthalpy per unit mass: Taking potential and kinetic energy terms into account,Heat Capacities,Heat Capacities,For a closed system at constant volume (d V=0, isochoric) Cv heat capacity at constant volume,For a closed system at constant pressure (d P=0,

16、 isobaric) Cp heat capacity at constant pressure,The difference between Cp and Cv, a matter of mathematical deduction., for ideal gas, the difference of the specific heat capacity is R,Element Capacity: Dulong-Petit Law Compound Capacity: Kopp Law,equations of state,Equations of state for Ideal gas

17、Boyle law (no change in temperature): P 1/V Charles law (no change in pressure): V T Gay-Lussac (no change in volume): P T V=0.0224141m3, Pressure 101325Pa, Temperature273.15K,The characteristic of an ideal gas,internal eternal energy does not change with volume at constant temperature enthalpy does not change with volume at constant temperature The difference between Cp and Cv, a matter of mathematical deduction is R.,Joules experiment (Q=0, W=0) Work was performe