Contact Angle 0 of Liquids on Solid Surfaces

When 0 is less than 90° the surface is wetting (such as water on glass) 

It is also known that by the treatment of glass surface by using suitable chemicals, the surface can be rendered hydrophobic. This is the same technology as used in many utensils, which are treated with teflon or similar items. 

As already mentioned, a solid in contact with a liquid leads to interactions related to the surfaces involved. The solid surface is being brought in contact with surface 

FIGURE 5.4 Apparent or true contact angle of a liquid drop on a rough solid surface. 

Contact angles, 9, of Water on Different Solid Surfaces (25°C) 

The relationship Young s equation describes is the interplay of forces (liquid surface tension, solid surface tension, liquid-solid surface tension) at the three-phase boundary line. It is regarded as if these forces interact along a line. Experimental data show that this is indeed true. The magnitude of 9 is thus only dependent on the molecules nearest the interface, and is independent of molecules much farther away from the contact line. 

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