Asklemmy

43908 readers

1057 users here now

A loosely moderated place to ask open-ended questions

Search asklemmy 🔍

If your post meets the following criteria, it's welcome here!

Open-ended question
Not offensive: at this point, we do not have the bandwidth to moderate overtly political discussions. Assume best intent and be excellent to each other.
Not regarding using or support for Lemmy: context, see the list of support communities and tools for finding communities below
Not ad nauseam inducing: please make sure it is a question that would be new to most members
An actual topic of discussion

Looking for support?

Looking for a community?

Lemmyverse: community search
sub.rehab: maps old subreddits to fediverse options, marks official as such
[email protected]: a community for finding communities

~Icon~ ~by~ ~@Double_[email protected]~

founded 5 years ago

MODERATORS

[email protected]

Where does the energy come from to lift water by osmosis? (feddit.uk)

submitted 2 weeks ago* (last edited 2 weeks ago) by [email protected] to c/[email protected]

14 comments fedilink hide all child comments

For example in a tree, the water is lifted from the high concentration in the soil to the low concentration higher up in the tree. But at the end of that process the water has been elevated, which should take energy (=mgh), but it seems like it kind of gets lifted for free without spending any energy?

Similarly, dipping a paper towel into a bowl of water, the water "climbs" the towel (by capillary action?) and absorbs upwards, meaning the water was lifted upwards (so gained potential energy) seemingly for free?

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 2 points 2 weeks ago

I don't remember all of the details, but I thought it was essentially the water's surface tension that foots the energy bill when climbing a paper towel or a capillary in a tree.

The surface of fluids like water are unhappy. Molecules on the surface would much rather be deep in the fluid because on the surface they have "dangling" Van der Waals & polar bonds to one side. You can calculate the potential energy of the surface due to all of those dangling weak bonds, & that's the energy that is used to climb a capillary (the energy isn't free).

I could be misremembering though, I admit. School was many years ago...