7 upvotes, 1 direct replies (showing 1)
View submission: Is sand a liquid???
What defines a liquid is its tendency to deform continuously under a continuous shear force.
If you take a bucket of (dry) sand and drop it, it'll form a mound. Fun fact: The angle of the mound relative to level ground is called the angle of repose.
Gravity is acting on it continously, but it no longer deforms.
We will "flow" sand by
While in a slurry forum, it can act like a liquid, but it's really just a bunch of solids hanging around inside a gel or paste.
It's worth noting that with a little water added, sand acts more solid than sand is.
By that token, toothpaste, paint, etc aren't strictly liquid, either, but a mishmash of liquid and solids, too, taking properties of both.
Comment by Chemomechanics at 17/01/2024 at 00:52 UTC
2 upvotes, 0 direct replies
What defines a liquid is its tendency to deform continuously under a continuous shear force.
I’ll add an important qualifier: over the time scale of interest/relevance. Solids creep[1]—exhibit viscous flow—in response to a load, including their own weight. Familiar examples include glaciers, lead pipes, and elastomers, all of which progressively slump over decades or faster. Because we like our solid structures to stay in place, we routinely engineer this aspect away through various strategies, including alloying, crosslinking, grain size maximization, and temperature minimization.