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Interesting Physics Conundrum

Here's something to get your brain whirring. This came up in conversation with my Uncle over the weekend.

As you know, work consumes energy. So you have to put energy in to a system to get work out.

Cooling a substance removes energy.

Water expands when frozen. So, when water is trapped in a crack in a rock, or road surface, it pushes the crack apart as it freezes. Therefore, it does work.

So how does removing energy from a system cause it to do work?

Think about that for a while ;)

It is still a transfer of energy.

Quote:

Originally Posted by DanielDudley (Post 9359224)

It is still a transfer of energy.

ding ding

How about this: (someone school me where I am wrong and I deserve handicap points for not looking it up!) :)

The bonding forces of what gets destroyed (rock split/radiator burst/ etc.) is LESS than the bonding forces/ energy of Frozen water which is LESS than the energy in liquid water.

Water is a polar molecule, and as a liquid, has the ability to reorient itself into the most compact package possible (like people packing into a crowded bus). When heat energy is lost, water goes through a phase change into a solid, and those molecules cannot move about as they did before. Frozen, they cannot reorientate themselves to pack themselves as dense around one another... hence, ice expands, and being less dense. floats on liquid water.

As these frozen water molecules take up their new (less compact and more space requiring status), they still have a hell of a lot of strength/energy, which overloads the strength of the copper pipes in your house/ whatever, and they burst...

Does that sound good? I am sure I am misstating something here...This is just a guess on my part

I assume that ice has a crystalline structure. I don't really know much about atomic forces, but I expect there is some considerable attraction. Even so, atoms take in energy during a change of state from solid to liquid, and liquid to gas, and they spend energy changing back.

You put energy into a battery, and when you spend it, it will turn a motor, or cause a wire to glow. When you spend energy making a solid, perhaps not all of that energy is spent as heat production, and that would imply that it could do useful work in directions other than making other molecules more energetic. That energy could also orient molecules. A final punch into shape as it were.

Study the temperature changes when water changes phases. it can go well below freezing before it actually starts freezing, then warms as it goes solid.

Same when it melts. It has to absorb a great deal of energy and go over 32 degrees to actually melt.

I worked on a project back in the 80's to STORE that phase change energy at night and use it to cool during The day.
They used a spacial salt water that exaggerated the delta T for the phase changes. Neat stuff.

Zero Energy Offices, phase change materials for hvac applications

EDIT: the temperature does not change during phase change, but the amount of energy absorbed or given up swings during phase change. Ice absorbs a great deal of energy while it melts, and water gives off a great deal of energy as it freezes.
that's what i meant but did not remember all the details.

Okay, I couldn't take it anymore and googled it. Still looking for the specific energy path, but as far as water going to ice- as usual I was wrong!

The Expansion of Water Upon Freezing

https://en.wikipedia.org/wiki/Ice#Rime_ice

This at least explains the crystalline structure taking more space.
Still searching for an exact energy pathway/explanation. They best answer I am seeing in chat groups so far is the potential energy of liquid water is mostly dissipated as heat, but some energy is converted into the work necessary have the ice expand something. Still looking for a nice flowchart of some sort!

When I was in high school one of my friends was fascinated with the pressure ice can create. He kept trying to make an enclosure that could contain the pressure. Of course there was no internet but I looked it up in our encyclopedia and I bet him 20 bucks he could not do it. He sure split a lot of pipes and what looked like a pipe bombs and other containers trying to contain water freezing into ice. He never did pay me my 20 bucks because he said he was not ready to give up.

Now days I wonder if the store would sell the makings of a pipe bomb to a teenager. All he did was put water in it and let it freeze.

I wonder how many BTUs of energy would need to be extracted to effect the phase change if the ice was not doing work while the H2O restructured. I suspect fewer. It's been a long time since I studied physics and I don't have time to look it up right now, but I think the specific heat capacity of water would be lower if it did not physically expand (and do work) while changing phase.
Comparing it with a hypothetical substance that does not expand when changing phase.

BTUs to lower i gram of hypothetical substance 1 degree = X

BTUs to lower i gram of H2O 1 degree = 2X

Quote:

Originally Posted by GH85Carrera (Post 9359923)

how about a balloon?

Many different types of ice...

Quote:

Amorphous ice - an ice lacking crystal structure. Amorphous ice exists in three forms: low-density (LDA) formed at atmospheric pressure, or below, high density (HDA) and very high density amorphous ice (VHDA), forming at higher pressures. LDA forms by extremely quick cooling of liquid water ("hyperquenched glassy water", HGW), by depositing water vapour on very cold substrates ("amorphous solid water", ASW) or by heating high density forms of ice at ambient pressure ("LDA").

Ice Ih
Normal hexagonal crystalline ice. Virtually all ice in the biosphere is ice Ih, with the exception only of a small amount of ice Ic.

Ice Ic
A metastable cubic crystalline variant of ice. The oxygen atoms are arranged in a diamond structure. It is produced at temperatures between 130 and 220 K, and can exist up to 240 K, when it transforms into ice Ih. It may occasionally be present in the upper atmosphere.

Ice II
A rhombohedral crystalline form with highly ordered structure. Formed from ice Ih by compressing it at temperature of 190–210 K. When heated, it undergoes transformation to ice III.

Ice III
A tetragonal crystalline ice, formed by cooling water down to 250 K at 300 MPa. Least dense of the high-pressure phases. Denser than water.

Ice IV
A metastable rhombohedral phase. It can be formed by heating high-density amorphous ice slowly at a pressure of 810 MPa. It doesn't form easily without a nucleating agent.[58]

Ice V
A monoclinic crystalline phase. Formed by cooling water to 253 K at 500 MPa. Most complicated structure of all the phases.

Ice VI
A tetragonal crystalline phase. Formed by cooling water to 270 K at 1.1 GPa. Exhibits Debye relaxation.

Ice VII
A cubic phase. The hydrogen atoms' positions are disordered. Exhibits Debye relaxation. The hydrogen bonds form two interpenetrating lattices.

Ice VIII
A more ordered version of ice VII, where the hydrogen atoms assume fixed positions. It is formed from ice VII, by cooling it below 5 °C (278 K).

Ice IX
A tetragonal phase. Formed gradually from ice III by cooling it from 208 K to 165 K, stable below 140 K and pressures between 200 MPa and 400 MPa. It has density of 1.16 g/cm3, slightly higher than ordinary ice.

Ice X
Proton-ordered symmetric ice. Forms at about 70 GPa.

Ice XI
An orthorhombic, low-temperature equilibrium form of hexagonal ice. It is ferroelectric. Ice XI is considered the most stable configuration of ice Ih. The natural transformation process is very slow and ice XI has been found in Antarctic ice 100 to 10,000 years old. That study indicated that the temperature below which ice XI forms is −36 °C (240 K).

Ice XII
A tetragonal, metastable, dense crystalline phase. It is observed in the phase space of ice V and ice VI. It can be prepared by heating high-density amorphous ice from 77 K to about 183 K at 810 MPa. It has a density of 1.3 g cm−3 at 127 K (i.e., approximately 1.3 times more dense than water).

Ice XIII
A monoclinic crystalline phase. Formed by cooling water to below 130 K at 500 MPa. The proton-ordered form of ice V.

Ice XIV
An orthorhombic crystalline phase. Formed below 118 K at 1.2 GPa. The proton-ordered form of ice XII.

Ice XV
The proton-ordered form of ice VI formed by cooling water to around 80–108 K at 1.1 GPa.

Ice XVI
The least dense crystalline form of water, topologically equivalent to the empty structure of sII Clathrate hydrates.

Your looking at this problem backwards.

The rock was doing the work every day until the cooling ice removed its energy and the rock relaxed its grip :)

And heat-shrink tube contracts when heated. :eek: Now what? Everyone knows heat causes expansion. ;)

Anyway... wayner is kind of right; rock actually releases it's grip. That is, even rock flexes, and has relatively weak tension carrying abilities.

In my mind the key here is just like boiling water at room temperature (aka evaporation) one needs to consider the random distribution of molecular speeds. --the bulk may have an average temp, but each molecule is likely not at average energy (vibe speed). In the case of rock breaking ice, This internal energy dance allows localized creation of the more voluminous (pressure building) ice structure.

IOW, stop considering the bulk energy.

Here is a fun weirdocity, ice is slippery because molecules near the surface vibrate only up and down, making a molecular vibe-table. Crazy stuff, H<sub>2</sub>O

If you built a container to freeze water that could hold high pressure the water would never freeze, the high pressure would keep the water from turning into a solid state and expanding.

Its the opposite, if you put water in a vacuum chamber it will boil at room temperature and start too cool as the energy is removed from the water.

Water is very different...

Quote:

Researchers described the new molecular state in the journal Physical Review Letters.
OAK RIDGE, Tenn., April 25 (UPI) -- Scientists at the Department of Energy's Oak Ridge National Laboratory have observed water molecules behaving unlike gas, liquid or solid states.

Researchers discovered the new state while subjecting water molecules to extreme confinement.
When water molecules were pushed into nanoscale tubes or channels in the mineral beryl, the water molecules become delocalized around a ring, with each molecule adopting "an unusual double top-like shape."
"This means that the oxygen and hydrogen atoms of the water molecule are delocalized and therefore simultaneously present in all six symmetrically equivalent positions in the channel at the same time," lead study author Alexander Kolesnikov, of ORNL's Chemical and Engineering Materials Division, said in news release. "It's one of those phenomena that only occur in quantum mechanics and has no parallel in our everyday experience."

This spreading of water molecules when confined was not just unexpected, it breaks the rules of classical physics. The behavior, known as "tunneling," describes a molecule passing through a barrier without the energy required to do so -- in other words, it defies physics.

"The average kinetic energy of the water protons directly obtained from the neutron experiment is a measure of their motion at almost absolute zero temperature and is about 30 percent less than it is in bulk liquid or solid water," Kolesnikov said. "This is in complete disagreement with accepted models based on the energies of its vibrational modes."

Because the confinement measured at ORNL is comparable to the experience of water molecules trapped in rocks, soil and cell walls, the novel findings are expected to have real-world impact on the discussions happening within a variety of scientific disciplines -- cellular biology, geology and more.

Or perhaps holding the water @ temp to create its liquid state is energy spent.
It will go back to its natural state of frozen without the work to keep it heated .. .

Our entire ecosystem is based on the unique properties of water which cause it to expand when frozen and become buoyant in liquid water. (I read that somewhere anyway)

The easiest to understand reason for waters expansion and extra energy when expanding when it changes from liquid to solid.

There are molecular electrical like charge repulsion forces between water molecules. When water is liquid the movement of the molecules overcome the repulsive forces allowing the molecules to pack closer together. As they slow to become a solid the repulsive forces have more effect increasing the volume with more force than is available in the reaction.

Quote:

Originally Posted by Soren Lorenson (Post 9364436)

Our entire ecosystem is based on the unique properties of water which cause it to expand when frozen and become buoyant in liquid water. (I read that somewhere anyway)

Correct. Life would not exist as we know it without this unusual property. Without it, water would freeze from the bottom of a lake up and never completely thaw. On the surface, it usually thaws with warmer weather.

Quote:

Originally Posted by Steve Carlton (Post 9364702)

Correct. Life would not exist as we know it without this unusual property. Without it, water would freeze from the bottom of a lake up and never completely thaw.

I'm not buying that. The source of the heat sink (cold atmospheric air) only impinges on the surface. Why should the effect occur at the bottom, where the surrounding surface is warmer.

Quote:

Originally Posted by wdfifteen (Post 9364769)

I'm not buying that. The source of the heat sink (cold atmospheric air) only impinges on the surface. Why should the effect occur at the bottom, where the surrounding surface is warmer.

The frozen water would sink. Imagine the polar ice cap if it weren't buoyant, plop to the bottom of the ocean.

Think of boiling water in a pan, the heat source is at the bottom, yet the steam rises through the water into the atmosphere.