**Ask a monkey a physics question thread**

[MadMojoMonkey]

I feel like states of matter are relatively arbitrary. I was taught in high school chemistry that glass is technically a liquid that flows unbelievably slowly, and that this could be observed in old houses, where the panes of glass are somewhat thicker at the bottom than at the top, due to creep.

I heard that before, too, but I don't think it's actually true.

Nope.

unlike the molecules in conventional liquids, the atoms in glasses are all held together tightly by strong chemical bonds. It is as if the glass were one giant molecule.

From: The 'glass is a liquid' myth has finally been destroyed

Is every solid somewhat amorphous like this, or is there some sort of boundary where a solid is truly solid and a liquid or amorphous solid is something different?

I think this is answered above. Let me know or restate it if not.

I would imagine that diamond is a solid in the purest sense of the word, so does it have something to do with having a crystalline structure?

A crystalline structure is definitely not a liquid, as the spacing and arrangement of the atoms defines the crystal. This is another "like a giant molecule" case, but it's really not, since the bonds are quite different

That feels iffy... I'm soft on chemistry, ultimately. (Is Chemist here?)

I know from a liquid to a gas there's a clear difference because gases can be compressed to change volume and liquids cannot.

It's all about the fact that in a gas there are no inter-molecular bonds because the kinetic energy of particle collisions is greater than the bonding energy.

In a liquid, there are weak inter-molecular bonds. In a solid, there are strong inter-molecular bonds.

Since the particles in a gas aren't bound together, they're not "touching", and there is space between them. So by compressing the volume, you're reducing the space between particles.

In liquids and solids, the atoms/molecules are bound to their neighbors already, so in order to compress them, you have to squish them closer together than they are. Quantum Mechanics has some stuff to say about that, and the reaction force rises rapidly with slight distortions.

I'll stop babbling.

How dare you, sir!

[chemist]

I never studied phsyics or chemistry in any detail at school, which is a huge shame because it interests me so much. So my understanding of physics is pretty much thanks to intuition and internet, which means it's heavily flawed and limited. But I'd still bet it's a better grasp than most uneducated folk. I would love to study phsyics properly.

You didn't miss anything at school.
Nelkon & Parker was the standard A-Level textbook.
https://archive.org/details/AdvancedLevelPhysics
Read it and yawn. The joys of calculating angular momentums without any practical reason.

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I feel like states of matter are relatively arbitrary. I was taught in high school chemistry that glass is technically a liquid that flows unbelievably slowly, and that this could be observed in old houses, where the panes of glass are somewhat thicker at the bottom than at the top, due to creep.

That feels iffy... I'm soft on chemistry.

Actually it is pure physics. Viscosity at room temperature.
In the American Journal of Physics, materials engineer Edgar D. Zanotto predicted the relaxation time for Germanium Dioxide at room temperature would be 10 to the power of 32 years, (that's a few billion and a few more zeros), which is quite a bit longer than our universe has been around.
Silicon Dioxide Glass is an even thicker liquid so would flow even slower at standard Ts and Ps. The old house would have to be in another much older universe to observe any creep.

What's the difference between an amorphous solid and a non-Newtonian fluid?
Is this why ketchup doesn't come out of the bottle?
If you bang it too hard would the bottle flow as well?
Could the ketchup and bottle form a colloidal suspension?
Is Renton correct that states of matter can appear relatively arbitrary?

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The Coulomb force ... is stylistically no different from Newton's Law of Gravitation.

We like the electrical permittivity of free space.

[MadMojoMonkey]

What's the difference between an amorphous solid and a non-Newtonian fluid?

You're throwing me softballs, now.

Proof Non-Newtonian fluids are awesome.
This is not in English, but it doesn't matter. They have a decent sized pool of (I'm guessing) oobleck, or cornstarch and water.
Skip to 1:30 for the part where 1 person is submerged in the pool while another is running on the surface.

Making oobleck is a great way to kill an hour with any age group who hasn't played with it before.
I mean ANY age group - from toddlers up to "Am I dead yet?"

I'll talk about the physics in another post.

Is this why ketchup doesn't come out of the bottle?

Ketchup is a normal, Newtonian, viscous fluid.

Viscosity is "resistance to flow" and ketchup has it. It also has surface tension which tends to hold the surface of the fluid in place.
When you try to pour an old-fashioned glass ketchup bottle, especially if it's new, and full, with a smaller surface area, then the viscosity and surface tension teem up to restrict the flow of the ketchup in the small gap.

If you turn the bottle so point downwards and shake it, you have another problem. The whole mass of ketchup wants to move out the opening, but in so attempting, it creates a vacuum pressure behind it, which prevents it from flowing. The viscosity is thick enough to prevent "glugging" for a surface area that small.

If you lay the bottle sideways and give it a gentle back-and-forth wiggle, you can get the surface tension to break, and the ketchup will start to flow. Alternatively, you could just use a knife or any pokey-tool to mark the smooth surface of the ketchup in the bottle, and it would then flow.

If you bang it too hard would the bottle flow as well?
Could the ketchup and bottle form a colloidal suspension?

I think those are possible only if you bang it hard enough to pulverize the glass into sand, but I fear you're trying to trick me.

Is Renton correct that states of matter can appear relatively arbitrary?

Absolutely. There is gray area in this, and Renton is only talking about the 4 most common states of matter. We've not discussed super-critical fluids, or the super-fluid state of Helium, or the semi-fluid behavior of sand.

Atoms bond to each other in some blend of ionic and covalent bonding. It's never purely one or the other. Molecules bond many atoms together, with various strengths of ionic/covalent at each bond. It is the nature of the inter-atomic and inter-molecular bonds that determines the characteristics of a substance, along with temp., pressure, density.