Why do things get wet more easily than dry?

Question

For instance, why does a towel soak up water (i.e. 'suck water into places where air previously was) much more quickly than it dries (i.e. sucks air into places where water used to be)? It only takes an instant for something to get wet, but a long time to get dry.

Is this a common for other liquids and other porous solids - what about if you poured mercury onto a slice of bread? What if you poured rubbing alcohol onto a clay pot? Does this situation still hold true? Does temperature have anything to do with it? What about molten lead and a slab of very hot (but not molten) granite?

Just curious! Thanks!!!

Answer 1

A towel takes up water in a process akin to capillary attraction. The towel dries through evaporation and is affected by temperature and surface tension in the droplets. Evaporation involves a matter state change - from liquid to vapor, with all the energy considrations that that entails even at room temperature.

A towel wetted with alcohol will dry considerably faster due the the higher vapor pressure and lower temperature required to change from liquid to vapor as compared to water.

Mercury into bread is a different issue. The bread is unlikly to absorb much if any of the liquid and get "wet". Additionally, mercury has a much higher vaporization temperature, higher surface tension, than water so at room temperature would take decades at least to evaporate.

Molten lead will not "wet" hot granite in the same sense that water wets a towel (or in any other sense that I can think of) so the principle does not apply.

Answer 2

A towel becomes wet through contact, but it becomes dry through evaporation. The towel's contact with water is instantaneous. However, it takes a long time for water to evaporate into air at room temperature. (It goes faster at higher temperatures.) They are completely different processes. Instead, take note that if you wipe paper towels over a spill, the paper towels become wet very quickly, but the countertop also becomes dry very quickly! That's because they are caused by the same process, which is the absorption of liquid water.

Answer 3

Wet food is better for your cat, it's more healthy and doesn't have as much filler as many of the dry foods. I feed my 2 year old cat a mixture of both, wet food as his main source of food and then a small bowl of dry food that I got from the vet that helps keep his teeth clean. Good luck!

Answer 4

I would guess it has to do with the amount of moisture and air flow in the air. A wet towel will dry pretty quick on a windy day in the hot desert.