版权所有：华东理工大学物理化学教研室 11 2). The conservation of energy w>0 or q>0, energy is transferred to the system as work or heat. w <0 or q<0, energy is lost from the system as work or heat. △U = q + w —the First Law of thermodynamics If write w for the work done on a system, q for the energy transferred as heat to a system, and △U for the resulting change in internal energy, then it follows that The internal energy of a system may be changed either by doing work on the system or by heating it. 2.2 The First Law
版权所有：华东理工大学物理化学教研室 11 2). The conservation of energy w>0 or q>0, energy is transferred to the system as work or heat. w <0 or q<0, energy is lost from the system as work or heat. △U = q + w —the First Law of thermodynamics If write w for the work done on a system, q for the energy transferred as heat to a system, and △U for the resulting change in internal energy, then it follows that The internal energy of a system may be changed either by doing work on the system or by heating it. 2.2 The First Law
版权所有：华东理工大学物理化学教研室 12 3). The formal statement of the First Law The work needed to change an adiabatic system from one specified state to another specified state is the same however the work is done. wad =Uf - Ui =△U h =Af - Ai =△A The same quantity of work must be done on an adiabatic system to achieve the same change of state even though different means of achieving that work may be used. 2.2 The First Law
版权所有：华东理工大学物理化学教研室 12 3). The formal statement of the First Law The work needed to change an adiabatic system from one specified state to another specified state is the same however the work is done. wad =Uf - Ui =△U h =Af - Ai =△A The same quantity of work must be done on an adiabatic system to achieve the same change of state even though different means of achieving that work may be used. 2.2 The First Law
版权所有：华东理工大学物理化学教研室 13 Work and heat 2.3 Expansion work 1). The general expression for work 2). Free expansion 3). Expansion against constant pressure 4). Reversible expansion 5). Isothermal reversible expansion 2.4 Heat transactions 2.5 Enthalpy 2.6 Adiabatic changes
版权所有：华东理工大学物理化学教研室 13 Work and heat 2.3 Expansion work 1). The general expression for work 2). Free expansion 3). Expansion against constant pressure 4). Reversible expansion 5). Isothermal reversible expansion 2.4 Heat transactions 2.5 Enthalpy 2.6 Adiabatic changes
版权所有：华东理工大学物理化学教研室 14 2.3 Expansion work dU = dq + dw If the work done on a system is dw and the energy supplied to it as heat is dq, the infinitesimal change of internal energy dU is: Infinitesimal form
版权所有：华东理工大学物理化学教研室 14 2.3 Expansion work dU = dq + dw If the work done on a system is dw and the energy supplied to it as heat is dq, the infinitesimal change of internal energy dU is: Infinitesimal form
版权所有：华东理工大学物理化学教研室 15 1). The general expression for work dw = −Fdz The work required to move an object a distance dz against an opposing force of magnitude F is The negative sign presents that when the system moves an object against an opposing force, the internal energy of the system doing the work will decrease 2.3 Expansion work
版权所有：华东理工大学物理化学教研室 15 1). The general expression for work dw = −Fdz The work required to move an object a distance dz against an opposing force of magnitude F is The negative sign presents that when the system moves an object against an opposing force, the internal energy of the system doing the work will decrease 2.3 Expansion work