版权所有：华东理工大学物理化学教研室 21 6.2 Phase boundaries 5). Melting and freezing points The melting freezing temperature: the temperature at which, under a specified pressure, the liquid and solid phases of a substance coexist in equilibrium is called. The normal melting and freezing point: The temperature when the pressure is 1atm is called the normal melting and freezing point. The standard melting and freezing point: the melting and freezing point when the pressure is 1 bar
版权所有：华东理工大学物理化学教研室 21 6.2 Phase boundaries 5). Melting and freezing points The melting freezing temperature: the temperature at which, under a specified pressure, the liquid and solid phases of a substance coexist in equilibrium is called. The normal melting and freezing point: The temperature when the pressure is 1atm is called the normal melting and freezing point. The standard melting and freezing point: the melting and freezing point when the pressure is 1 bar
版权所有：华东理工大学物理化学教研室 22 6.2 Phase boundaries 6). The triple point There is a set of conditions under which three different phases of a substance all simultaneously coexist in equilibrium. It is represented by the triple point, a point at which the three phase boundaries meet. The temperature at the triple point is denoted T3. The triple point of a pure substance is outside our control: it occurs at a single definite pressure and temperature characteristic of the substance. The triple point of water lies at 273.16 K and 611 Pa
版权所有：华东理工大学物理化学教研室 22 6.2 Phase boundaries 6). The triple point There is a set of conditions under which three different phases of a substance all simultaneously coexist in equilibrium. It is represented by the triple point, a point at which the three phase boundaries meet. The temperature at the triple point is denoted T3. The triple point of a pure substance is outside our control: it occurs at a single definite pressure and temperature characteristic of the substance. The triple point of water lies at 273.16 K and 611 Pa
版权所有：华东理工大学物理化学教研室 23 Phase diagrams 6.1 The stabilities of phases 6.2 Phase boundaries 6.3 Three typical phase diagrams Phase stability and phase transitions 6.4 The thermodynamic criterion of equilibrium 6.5 The dependence of stability on the conditions 6.6 The location of phase boundaries 6.7 The Ehrenfest classification of phase transitions The physical liquid surface 6.8 Surface tension 6.9 Curved surfaces 6.10 Capillary action 6. Physical transformation of pure substances
版权所有：华东理工大学物理化学教研室 23 Phase diagrams 6.1 The stabilities of phases 6.2 Phase boundaries 6.3 Three typical phase diagrams Phase stability and phase transitions 6.4 The thermodynamic criterion of equilibrium 6.5 The dependence of stability on the conditions 6.6 The location of phase boundaries 6.7 The Ehrenfest classification of phase transitions The physical liquid surface 6.8 Surface tension 6.9 Curved surfaces 6.10 Capillary action 6. Physical transformation of pure substances
版权所有：华东理工大学物理化学教研室 24 1). Water -low pressure The phase diagram Triple point: T3=273.16K(p=0.006atm) The metastable phase Thermodynamically unstable phases that persist because the transition is kinetically hindered are called metastable phases. b a c o Ice Water 1 . 0 Tf Tb e Normal freezing point Tf=273.15K(p=1.0atm) Normal boiling point Tb=373.15K(p=1.0atm) Critical point Tc=674.30K(p=218.3atm) T3 Tc 6.3 Three typical phase diagrams
版权所有：华东理工大学物理化学教研室 24 1). Water -low pressure The phase diagram Triple point: T3=273.16K(p=0.006atm) The metastable phase Thermodynamically unstable phases that persist because the transition is kinetically hindered are called metastable phases. b a c o Ice Water 1 . 0 Tf Tb e Normal freezing point Tf=273.15K(p=1.0atm) Normal boiling point Tb=373.15K(p=1.0atm) Critical point Tc=674.30K(p=218.3atm) T3 Tc 6.3 Three typical phase diagrams
版权所有：华东理工大学物理化学教研室 25 6.3 Three typical phase diagrams 1). Water-high pressure The experimentally determined phase diagram for water At high pressures, different structural forms of ice come into stability. Some of these phases which are called ice II, III, V, VI, and VII melt at high temperatures. Note that five more triple points occur in the diagram other than the one where vapour, liquid, and ice I coexist. Each one occurs at a definite pressure and temperature that cannot be changed
版权所有：华东理工大学物理化学教研室 25 6.3 Three typical phase diagrams 1). Water-high pressure The experimentally determined phase diagram for water At high pressures, different structural forms of ice come into stability. Some of these phases which are called ice II, III, V, VI, and VII melt at high temperatures. Note that five more triple points occur in the diagram other than the one where vapour, liquid, and ice I coexist. Each one occurs at a definite pressure and temperature that cannot be changed