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After I was drinking water in school, I flipped top-to-bottom the bottle. At that time, I was wondering how it is possible to form the water droplets on top of the bottle; inside the bottle. I searched for some information about water's force; Capillary action, Surface Tension. I thought that capillary action is the key to solve this problem. The reason for capillary action is related to polarity, but there is no polarity in plastic.

If I flipped top-to-bottle the bottle, some water droplet form on the top of the plastic bottle. The gravity pulls the water droplet, but it still is hanging on.

How it is possible? Is there another force?

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    $\begingroup$ I'm sorry, the question isn't quite clear to me. By 'reversed', do you mean flipped top-to-bottom? Also, are the droplets on the inside or outside? For future reference, please do consider framing your questions in a more understandable way. $\endgroup$
    – wavion
    Commented May 29, 2020 at 13:32
  • $\begingroup$ I'm sorry for you. I am not used to writing English because I'm Korean student. I am trying to practice my writing skill. I will edit my question as soon as possible. $\endgroup$
    – 정우남
    Commented May 29, 2020 at 13:37
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    $\begingroup$ It's all right, you can explain what you mean in simple words in the comments and I'll edit the question for you :-) $\endgroup$
    – wavion
    Commented May 29, 2020 at 13:39
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    $\begingroup$ Is it possible that adhesion is the phenomenon you are looking for ? The capillary effect stems from that when considering 'narrow' spaces. $\endgroup$
    – Martin
    Commented May 29, 2020 at 13:41
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    $\begingroup$ As you said but ignored , hyperphysics.phy-astr.gsu.edu/hbase/surten.html also this appstate.edu/~goodmanjm/rcoe/asuscienceed/background/waterdrops/… $\endgroup$
    – anna v
    Commented May 29, 2020 at 15:22

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Here are several ways this can happen.

Once a plastic bottle has been used for a while, its surface is no longer pure and clean but will slowly grow a layer of things like soap residue into which water vapor can be absorbed. At that point, water droplets will cling to the surface.

This can also happen in clean plastic where the surface has scratches or tiny pores in it. At the sharp edges of the scratch or pore, the contact angle for wetting can be met and a droplet will stick there.

Those same scratches and pores also furnish a place where contaminants (as noted above) can get trapped and not washed off. Droplets will form there as well for this reason.

If there is something like a scratch, pore, or contamination spot on the plastic surface, then every time you wet the surface, the droplets will stick in the same exact location on that surface. This is the clue that at that particular location, there is something "different" in the surface!

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  • $\begingroup$ The OP later clarified in the question's comments that they meant the inside of the bottle. I think that only (or majorly) the outside of the bottle would be subject to the phenomena you described... $\endgroup$
    – wavion
    Commented May 30, 2020 at 5:22
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    $\begingroup$ my explanation is experimentally testable. I a different parallel universe, I used to work in the field of wettability and have seen my share of strange things- on the outsides and insides of objects... $\endgroup$
    – niels nielsen
    Commented May 30, 2020 at 5:24
  • $\begingroup$ That sounds interesting...I thought that the inside of the bottle isn't subject to all the 'wear-and-tear', that's all...maybe you could clarify a little on that? Other than that, on reading some websites, I see you're absolutely correct :-). Thank you for your answer! $\endgroup$
    – wavion
    Commented May 30, 2020 at 5:28
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    $\begingroup$ if you scrub out a bottle with a brush, you will scratch the material. You can superheat water in a brand-new snapple bottle (glass) right after draining it, but it's almost impossible to do so if the bottle has been scrubbed and re-used. I used to produce superheat vapor explosions in microwave ovens using filtered DI water and fresh snapple bottles. quite dramatic... $\endgroup$
    – niels nielsen
    Commented May 30, 2020 at 5:32
  • $\begingroup$ Thank you so much! :) $\endgroup$
    – 정우남
    Commented May 30, 2020 at 11:11

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