页数：52页文件大小：3.58 MB来源： Atkins’PhysChem物理化学ppt课件
本课件讨论纯物质的相转变：比较同一物质不同相的稳定性与亚稳相，由化学势相等给出相平衡条件，导出克拉佩龙方程与克劳修斯-克拉佩龙方程，并按埃伦费斯特方式对相变分级。
相的稳定性
Phase diagrams 6.1 The st abilities of phases 6.2 Phase boundaries 6.3 Three typical phase diagrams Phase stability and phase transitions 6.4 The thermodynamic criterion of eqm. 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 surface 6.10 Capillary action
相的稳定性
the phase transitions of pure substances: The simplest application of thermodynamics Phase diagram is a map of p and T. 1. The interpretation of empirically determined phase diagram for a selection of substances. 2. The factors that determine the positions and shapes of phase boundaries.
How the vapour p varies with T How the melting point varies with p How various thermodynamic functions change when the transition occurs.
相的稳定性
Phase diagrams: 6.1 The st abilities of phases A phase of a substance is a form of matter that is uniform throughout in chemical composition and physical state. A phase transition, the spontaneous conversion of one phase into another phase, occurs at a characteristic T for a given p.
The transition temperature, Ttrs, is the temperature at
6.2 Phase boundaries The phase diagram shows the regions of p and T thermodynamically stable. The lines are called phase boundaries, Show the values
6.2 Phase boundaries a pure liquid substance in a closed vessel, the p of a vapour in eqm with the liquid is called the vapour pressure.
(a) Critical points and boiling points Boiling Standard boiling point, atpex = 1 bar Normal boiling po
In a closed vessel boiling... As T vapour pressure density of the vapour As T
(b) Melting points and triple points in eqm. a specific p liquid solid Melting (fusion) temp
(b) Melting points and triple points A pure substance, the triple point is outside our contr
6.3 Three typical phase diagrams The experimental phase diagram for water
6.3 Three typical phase diagrams The experimental phase diagram for carbon dioxide
6.3 Three typical phase diagrams The experimental phase diagram for Helium Superfluid: w
Phase stability and phase transitions All will be based on the molar Gibbs energy, Gm. The ch
6.4 The thermodynamic criterion of eqm. From 2 ndLaw, the chemical potential of a substance is
6.5 The dependence of stability on the conditions At low temperature solid substance the lowest chemical
(a) The temperature dependence of phase stability For pure substance: To bring about a phase transition:
(b) The response of melting to applied pressure In most cases For water
(c) The effect of applied pressure on vapour p When p is applied to a condensed phase, vapour pressure
(c) The effect of applied pressure on vapour p The relation: p (after applied pressure, Δ P) and p * μ
6.6 The location of phases boundaries When phases α and β are in eqm. μ α (p, T) = μ β (p, T)
When phases α and β are in eqm. d μ = - SmdT + Vmdpdp /
When melting (fusion) takes place, the Clapeyron equati
When vaporization takes place, the Clapeyron equation:
When sublimation takes place, the Clapeyron equation: d
To classify phase transitions into different types. 6.7
6.7 The Ehrenfest classification of phase transitions Δ
6.7 The Ehrenfest classification of phase transitions (
6.7 The Ehrenfest classification of phase transitions (
The physical liquid surface Liquids tends to minimize s
Now we link surface effects to the Helmholtz and Gibbs
Minimization of the surface are a of a liquid 6.9 Curved surfaces A curved surface Vapour pressure Ca
(a) Bubbles, cavities, and droplets Bubble: vapour and
(a) Bubbles, cavities, and droplets In bubble or cavity
(a) Bubbles, cavities, and droplets Curvature radius
(a) Bubbles, cavities, and droplets Kelvin equation: Δ
(b) Nucleation For a droplets of water at 25 ° Cr = 1 μ
6.10 Capillary action Capillary action: liquids tend to
(a) Capillary rise The adhesive force < cohesive force
(b) The contact angle Between the edge of the meniscus
(b) The contact angle
粘附功(work of adhesion) 在等温等压条件下，单位面积的液面与固体表面粘附时对外所作的最大功称为粘附功，它是液体能否润湿固体的一种量度。粘附功越大，液体越能润湿固体，液- 固结合得越牢。在粘附过程中，消失了单位液体表面和固体表面，产生了单位液- 固界面。粘附功就等于这个过程表面吉布斯能变化值的负值。 (b) The contact angle
粘附功(work of adhesion) (b) The contact angle
浸湿功(work of immersion) 等温、等压条件下，将具有单位表面积的固体可逆地浸入液体中所作的最大功称为浸湿功，它是液体在固体表面取代气体能力的一种量度。只有浸湿功大于或等于零，液体才能浸湿固体。在浸湿过程中，消失了单位面积的气、固表面，产生了单位面积的液、固界面，所以浸湿功等于该变化过程表面自由能变化值的负值。 (b) The contact angle
浸湿功(work of immersion) (b) The contact angle
内聚功(work of cohesion) 等温、等压条件下，两个单位液面可逆聚合为液柱所作的最大功称为内聚功，是液体本身结合牢固程度的一种量度。内聚时两个单位液面消失，所以，内聚功在数值上等于该变化过程表面自由能变化值的负值。 (b) The contact angle
内聚功(work of cohesion) (b) The contact angle
Exercises (a) 6.7, 9,11, 14,15 Problems: 6.1, 4,21 Homework
下载地址：{{downurl}}
{{{a}}}
{{#b}}{{{b}}}
{{/b}} {{/title}} {{#nolog}}登陆注册
{{/nolog}} {{#djsx}}点我刷新
{{/djsx}} {{#gocz}} {{/gocz}} {{#ffqr}} {{/ffqr}}