Why does water climb up a thin glass tube on its own, while mercury actually goes down?
It's capillarity, set by whether the liquid wets the glass.
It's capillarity, set by whether the liquid wets the glass. Water's adhesion to glass beats its cohesion, so it wets the tube and climbs (concave meniscus), h = 2Tcosθ/ρgr — the thinner the tube, the higher it rises. Mercury's cohesion is stronger than its adhesion, so it doesn't wet glass, forms a convex meniscus and is pushed down instead.
Key point
Narrow tube → larger capillary rise; wetting liquids rise, non-wetting ones fall.
Common mistake
assuming every liquid rises in a capillary.
Memory tip
water wets glass (rises); mercury doesn't (falls).
Tap to watch or see it right here — the app stays open (it only opens a quick search if nothing embeddable is found).