= Solution
On <Teflon>, the <water> drop has an obtuse <contact angle> and beads up, whereas the oil drop has an acute <contact angle> and spreads into a shallower patch. For small drops with negligible <Bond number>, both can be drawn as <spherical caps>.
To compare shape at equal volume $V$, let $R$ denote the generating sphere radius. The cap height and footprint radius are
$$
h=R(1-\cos\theta),\qquad s=R\sin\theta,\qquad
V=\frac\pi3 R^3(2-3\cos\theta+\cos^3\theta).
$$
For a fixed $V$, these relations give a taller, narrower drop for the larger <contact angle>. The angles are measured inside the liquid, including the obtuse angle of the water drop.
\Image[/past-exam-of-the-soft-condensed-matter-course-of-the-university-of-cambridge/2021-q5-droplets.png]
{title=Equal-volume <spherical caps> on <Teflon>}
{description=Original cross-sections comparing water at $102^\circ$ with oil at $25^\circ$. The same liquid volume is used to expose the difference in shape; no particular drop size or volume was supplied in the paper.}
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