The sci­ence be­hind the stick­i­ness of ice

Northwest Arkansas Democrat-Gazette - - STYLE -

Q: Why is ice sticky? A: Ice is sticky, but only to cer­tain kinds of sur­faces at cer­tain tem­per­a­tures. What re­ally hap­pens is that con­di­tions are just right for a shared ice layer to form be­tween the two sur­faces and link them.

A warm, damp tongue or slightly sweaty fin­ger can stick read­ily to an ice cube as the warmth tem­po­rar­ily melts ice at its sur­face; once the warmth has dis­si­pated, the wa­ter quickly re­freezes, cre­at­ing an icy link. If a cold, dry ob­ject touches the same ice cube, there is no melt­ing and no ad­he­sion.

Most of the time, how­ever, ice is slip­pery, as ice skaters and Antarc­tic penguins demon­strate. The slip­per­i­ness of ice has a more com­plex ex­pla­na­tion or com­bi­na­tion of ex­pla­na­tions.

It was long be­lieved that pres­sure melt­ing and fric­tional heat­ing in some com­bi­na­tion re­leased liq­uid wa­ter at the sur­face of the ice, so that sharp or even smooth ob­jects could glide across.

More re­cent re­search has also fo­cused on the idea that a per­ma­nent liq­uid-like layer lies atop the ice, even at tem­per­a­tures far be­low the freez­ing point.

And 2014 re­search pub­lished in the jour­nal PCCP, Phys­i­cal Chem­istry Chem­i­cal Physics, sug­gests that a com­mon su­per­solid skin, elas­tic and tem­per­a­ture sta­ble, cov­ers wa­ter and ice, and is re­spon­si­ble for its slip­per­i­ness.

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