What liquid is impossible to collect in a container and why?

Imagine a pleasant sunny day. Morning has just come and you go to the spring with a water bottle, bathing in the dew and enjoying the beautiful refraction of light rays in the drops. At the spring you see a trickle of clean water.

You place the bottle so that it can be filled with water and then you discover that the water does not collect, but all flows out through the walls! What’s even worse is that the water that still remains inside is trying to crawl back out, like a living creature.

It’s more like a dream with a flavor of the movie The Thing. But no, this is not a nightmare. Just you trying to fill a bottle with superfluid helium, and there are no walls for it. How does this work from a physics point of view and why do some liquids have no walls?

Liquid viscosity

Liquid – this is one of the aggregate states of matter, where the particles do not have a strict ordering, but they retain connections with each other. In this case, the volume is preserved, but the shape is not. Due to the fact that particles are connected to each other to one degree or another, a liquid has a property that called viscosity. Imagine a neocube that doesn’t have a particularly strong attraction between the links, but still allows the balls to stay close to each other.

Try mixing condensed milk and plain water with a spoon. Condensed milk is more viscous, so it is more difficult to mix. This means that the molecular bonds in its structure are strong enough to resist mixing and movement of layers within the system. Connections trying to “not let go of one particle from another”. The particles themselves also “rub” against each other, forming internal friction. This is the basic logic of the concept of “viscosity”.

What promotes the penetration of liquid into the pores

Now let’s go back to our example with the bottle at the very beginning.

Remember the sieve. If you try pour water into the sieve, it will naturally flow out of it. Large holes in the mesh are to blame. If you take water into a plastic basin, it will remain in this basin. What is the difference?

Healthy consider this process at the molecular level and everything will become obvious. If you look at the structure of plastic under a microscope, in many cases you can see micropores. Wherein the liquid that we collected into a basin made of such material will physically not be able to “get through” the micro-pores observed in the plastic.

The liquid molecule is larger than the pore itself. From the outside and at the macro level, we see it as a sealed container. It’s like sifting semolina through a sieve and then pouring peas into it. The peas will not fit through the sieve, although the semolina did. Here, peas are the equivalent of large particles of liquid in a plastic container with pores that are smaller than the particles. But this is just the tip of the iceberg. After all, the particle size in the example with superfluid helium does not change, and neither does the size of the aggregates.

Well, now let’s take a sieve through which water easily passed and fill it with condensed milk. Those particles that could fall into large holes are tied to those around them. This mass flows through the mesh with difficulty. It’s like pouring mastic from jar to jar.

Obviously, the higher the viscosity, the more difficult it is to pull the liquid through the sieve and vice versa. Internal communications will interfere with such a procedure. Therefore, even if a particle of liquid can get through the pore, then her existing environment will not allow her to do this.

Superfluidity and superfluid helium

We discussed all this for a reason. The key concept is viscosity. Imagine what’s possible the existence of a liquid without viscosity at all!

Her behavior will be characterized by the term superfluidity. Such a liquid can appear in laboratory conditions or when the indicated physical parameters are repeated outside the laboratory, which theoretically could happen somewhere in space.

An inquisitive reader will ask: How can a superfluid liquid exist at all? After all, in theory, its existence means that all connections between particles are completely absent. This will no longer be the same state of aggregation.

Here we are faced with quite complex physical model, which is explained through quantum interaction mechanisms. Moreover, as such, a complete explanation of the process still does not exist.

We need to extract the main thing – the absence of internal friction does not mean the absence of interaction and loss of connections between particles. Zero viscosity does not mean that the liquid will necessarily disintegrate into atoms. Quantum exchange mechanisms will come into play and keep this substance as a liquid.

But if a superfluid liquid gets into an ordinary sealed container, it will pass right through the walls. Approximately the same as water passing through a sieve.

The secret is that the container that we see as sealed is actually not sealed. It is covered with micropores in varying quantities. Between the particles that make up the walls, there is always some empty space.

Liquid with zero viscosity will pass perfectly through such pores. This is pretty much how it behaves superfluid helium.

Another very interesting behavior option is also possible. If superfluid matter suddenly cannot seep through the pores, then it will crawl along the wall. For her there is no friction and, alternately attracted to more and more new points on the surface of the container, the liquid particles will gradually crawl along the wall until the container is completely free.

So what is this magical helium?

Superfluid helium is a phase state of one of the isotopes of helium, in which it exhibits the properties of a liquid with zero viscosity. Consequently, it flows without friction over any surface and flows through any pores or discontinuities in the surface. The trick is that this substance does not fall apart into particles at zero viscosity.

Well, probably a logical question: A Is it only helium that can exhibit similar properties?? For a long time, scientists believed so. But relatively recently it became clear that many other elements, under certain conditions, demonstrate superfluidity properties.

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