(2)Stateand StatefunctionsState functions refer to functions which express thesystem state,such as V、P、m、E、U、H、G、SWhen the initial and final state is certain, the changeofits state function is the same状态函数的特点：“状态函数有特征，状态一定值一定，殊途同归变化等，周而复始变化零
6 (2) State and State functions State functions refer to functions which express the system state, such as V、 P 、 m、 E、U、H、G、S. When the initial and final state is certain, the change of its state function is the same. 状态函数的特点：“状态函数有特征，状态一定值一 定，殊途同归变化等，周而复始变化零。
(3) Heatand workBoth heat and work are forms of energy. Heat refersto the energy exchange between system andsurroundings caused by temperature change in whichthe energy is transferred by plenty of particlemovements without order. It is symbolized with Q. Onthe other side, work refers to the energy exchangebetween system and surrounding caused by otherfactors except temperature change in which theenergy is transferred by plenty of particle movementsin order. It is symbolized with W
7 (3) Heat and work Both heat and work are forms of energy. Heat refers to the energy exchange between system and surroundings caused by temperature change in which the energy is transferred by plenty of particle movements without order. It is symbolized with Q. On the other side, work refers to the energy exchange between system and surrounding caused by other factors except temperature change in which the energy is transferred by plenty of particle movements in order. It is symbolized with W
(4)Process and pathProcess means how a system changes from one stateto another. There are different kinds of process, suchas these below:IsothermalprocessIsobaric processIsovolumeprocessAdiabatic processCyclic processPath refers to the different way to complete a process
8 (4) Process and path Process means how a system changes from one state to another. There are different kinds of process, such as these below: Isothermal process Isobaric process Isovolume process Adiabatic process Cyclic process Path refers to the different way to complete a process
Internal energy5The sum of the energy in a system is calledinternal energy, its symbol is U.W?What is the relationship among△UandQ
9 (5) Internal energy The sum of the energy in a system is called internal energy, its symbol is U. What is the relationship among △U and Q、W?
1-2 The First Law of Thermodynamicsinitial state→final state△U= U, -U, =Q-WThe sign rule:When the system is endothermic,Qis positive+When the system do work on the surroundings, W is positive +10
10 1-2 The First Law of Thermodynamics initial state → final state U1 U2 △ U = U2 -U1 = Q – W The sign rule: When the system is endothermic, Q is positive +, When the system do work on the surroundings, W is positive +