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Unformatted text preview: small or very large, do the equations you derived in the ﬁrst two parts still apply?
6. We (hopefully) conducted an experiment in class with water and a capillary (1 mm outer and 0.85 mm inner diameter)
with three surface treatments: (a) the native glass (b) the native surface cleaned with oxygen plasma, and (c) the native
surface coated with silane. We measured capillary rise heights of roughly 20 mm, 33 mm, and -10 mm (we could not
see this one in class, but I ran another experiment and determined it to be this value) for the native, plasma cleaned,
and silane surfaces, respectively. Calculate the contact angles for these three cases and label them as hydrophilic or
hydrophobic. Draw schematics of the contact angle for cases (b) and (c).
2 7. A metal paper clip can be ﬂoated on the surface of water. Since the metal is more dense than water, it should have sunk
to the bottom, but because of surface tension it ﬂoated on a surface. The water surface becomes deformed resulting in
Solutions Manualthe Fluid M...
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