1
$\begingroup$

Imagine I have an iron tank with a $20~\mathrm{pm}$ hole on it. Then I completely fill it with water and use a pump to get the water out of that hole. What will come out, water or gas?

$\endgroup$
  • 1
    $\begingroup$ I've answered and also marked down. You have an ill-formed question. The hole size is physically unrealistic in real systems. It is on the order of the size of interstitial sites in lattices. What are you really wanting to determine here? $\endgroup$ – Jeffrey J Weimer Dec 24 '19 at 15:15
  • 2
    $\begingroup$ A 20 pm hole in an iron tank is not a hole. We are in the range of less than the typical atomic distance between the iron atoms of any of their possible metallic lattice structures that make up the tank. A typical atomic diameter is 1 Ångstrøm, which is 100 pm. $\endgroup$ – Steeven Dec 24 '19 at 16:58
7
$\begingroup$

Pressure alone does not break chemical bonds. Expose liquid water suddenly to a vacuum and it will vaporize as a molecule; it will not dissociate into atoms. This is true regardless of the initial pressure of the water.

The hole that you have made is too small for water molecules. It is even too small for a hydrogen atom, which is the smallest atom possible (with a radius of about 50-60 pm).

The hole size that you propose is more akin to the sizes of interstitial sites in solid lattices. For examples of the lattice structures of iron, see the links below.

https://en.wikipedia.org/wiki/Allotropes_of_iron

https://www.tf.uni-kiel.de/matwis/amat/iss/kap_4/backbone/r4_2_2.html

At this point, you should recognize that we cannot make a contiguous "hole" that is 20pm in radius or diameter through an iron wall. Indeed, this because of the way that atoms pack in solids, we cannot make such a hole through any solid wall that is thicker than two atoms stacked on in layers. The "holes" through the one layer of atoms are blocked by the atoms that cover in the next layer.

In essence, you have a solid tank. Nothing will transport through the wall.

| cite | improve this answer | |
$\endgroup$
  • 1
    $\begingroup$ In essence, you have a solid tank. Nothing will transport through the wall. Excellent summary! +1 from me. $\endgroup$ – Gert Dec 24 '19 at 15:18
  • $\begingroup$ @Jeffrey J Weimer I thought iron atom has 252 pm diameter. So it is possible to create a 20 pm hole into an iron tank. Can you plz tell me, What is the smallest size hole we can created in an opaque material? $\endgroup$ – user248881 Dec 24 '19 at 18:13
  • $\begingroup$ @user248881 The smallest diameter continuous (through-and-through) hole that we can create that will be self-supporting is likely on the order of a microns in diameter, perhaps to 100s of nm (tenths of microns). At that point with a macroscopically thick solid metal, it is also likely to be the boundaries of grains, not straight through and through. The answer is different for other classes of materials (ceramics, semiconductors, and polymers). Further discussion is worth a question of its own posting. $\endgroup$ – Jeffrey J Weimer Dec 24 '19 at 22:14
  • $\begingroup$ @Jeffrey J Weimer This is not off topic discussion since under my question you said, “Such a tiny hole is not possible”. So i wanted to know the exact diameter of the tiniest hole physicists can make in any solid opaque material which has the thickness of at least 1mm. But you didn’t gave me the exact digits. $\endgroup$ – user248881 Dec 25 '19 at 0:53
  • $\begingroup$ @user248881 The references I give about metal lattices give a starting point for you to learn about structures in metals. The answers to your new question can go in many directions, and an answer with exact digits is likely to be close to impossible to provide. Finally, I will say again, you are heading off-topic from your original post with your new question, your new question may be worthy of giving others an equal chance to address, and discussions are not the place to do so. $\endgroup$ – Jeffrey J Weimer Dec 25 '19 at 13:16
7
$\begingroup$

Your hole is too small to let even a single molecule through, but let's increase the hole to a size where molecules can come through one at a time. I'm sure this is what you had in mind. What then would be the result?

And the answer is that would have created a molecular beam. That is you would have a beam of isolated water molecules travelling away from the hole. The kinetic energy of the molecules would be about the thermal energy of $\tfrac32kT$. I make this a velocity of about 450 m/s.

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ No John! I intentionally selected that hole size because i wanted to know that, what will happen to a H2O molecule? Will the covalent bond between atoms of H and O break apart and hydrogen and oxygen gas will come out of it or nothing will come out of it? $\endgroup$ – user248881 Dec 24 '19 at 13:29
  • $\begingroup$ @user248881 Why do you think the $H-O$ bonds should break? We're talking about ordinary temperatures, right? $\endgroup$ – user8718165 Dec 24 '19 at 13:44
  • $\begingroup$ @user8718165 In my mind, pressure will break the bond. $\endgroup$ – user248881 Dec 24 '19 at 13:49
  • $\begingroup$ @user248881 I'm not sure if that's even possible. $\endgroup$ – user8718165 Dec 24 '19 at 13:50
  • $\begingroup$ @user8718165 I know that and that’s why i’m here to ask professional physicists who have played with atoms and it’s particles throughout their careers. $\endgroup$ – user248881 Dec 24 '19 at 14:05