The Fundamental Equation The work of forming a surface is additional to pV-work, and so we should regard it as a contribution to the Gibbs function of the system.Therefore in the presence of a system with a variable surface area dG=-SdT+VdP+Eugdng+YdAs This is the link with thermodynamics,and the reasoning about systems tending to smaller Gibbs functions can be applied to this equation.For instance,at constant T,P and N,a smaller value of the Gibbs function can be attained if the area is allowed to diminish.The condition for a natural change,dG<0,implies dA<0,which means that surfaces have a natural tendency to contract. PDF文件使用"pdfFactory Pro”试用版本创建替m.fineprint.com.cn
The Fundamental Equation The work of forming a surface is additional to pV-work, and so we should regard it as a contribution to the Gibbs function of the system. Therefore in the presence of a system with a variable surface area dG=-SdT+VdP+åmBdnB+ γdAs This is the link with thermodynamics, and the reasoning about systems tending to smaller Gibbs functions can be applied to this equation. For instance,at constant T ,P and N, a smaller value of the Gibbs function can be attained if the area is allowed to diminish. The condition for a natural change, dG<0, implies dAs <0, which means that surfaces have a natural tendency to contract. PDF 文件使用 "pdfFactory Pro" 试用版本创建 替www.fineprint.com.cn
The Effect Factors On the Surface Tension The nature of substance ·The contact phase Pressure and composition ·Temperature With the temperature increasing,usually the surface tension decreasing. PDF文件使用"pdfFactory Pro”试用版本创建fm,fineprint.com,cn
The Effect Factors On the Surface Tension • The nature of substance • The contact phase • Pressure and composition • Temperature With the temperature increasing, usually the surface tension decreasing. PDF 文件使用 "pdfFactory Pro" 试用版本创建 fwww.fineprint.com.cn
Wet Phenomena ·Touch wet ·Immerse wet ·Spread wet S=Ys-g-Yis-Y-g--spread coefficient S >0---the liquid can spread over the surface. S<0---the liquid does not wet the surface. PDF文件使用"pdfFactory Pro”试用版本创建wm,fineprint.com,c四
Wet Phenomena • Touch wet • Immerse wet • Spread wet S= γs-g- γl-s- γl-g ---spread coefficient S ³0--- the liquid can spread over the surface. S<0--- the liquid does not wet the surface. PDF 文件使用 "pdfFactory Pro" 试用版本创建 Ìwww.fineprint.com.cn
The Contact Angle - c777o77A 77 ds-1 《a）Wet surface (not wet surface The origin of the contact angle can be traced to the balance of forces at the line of contact between the liquid and the solid. Ys-g=YI-s+YI-gCOSO PDF文件使用"pdfFactory Pro”试用版本创建m,fineprint.com,cn
The Contact Angle The origin of the contact angle can be traced to the balance of forces at the line of contact between the liquid and the solid. γs-g= γl-s+ γl-gcosq PDF 文件使用 "pdfFactory Pro" 试用版本创建 Ìwww.fineprint.com.cn
Discussion: 0<0<90---the liquid wets the surface 90°<0<180°--the liquid does not wet the surface. PDF文件使用"pdfFactory Pro”试用版本创建wm,fineprint,com,cn
Discussion: • 0< q<90°---the liquid wets the surface •90°< q<180°---the liquid does not wet the surface. PDF 文件使用 "pdfFactory Pro" 试用版本创建 Ìwww.fineprint.com.cn