# 4 States of matter

## Main Question or Discussion Point

Based on Einsteins theory, e=mc2, would it be right to say that matter has 4 states?
Solid, Liquid, Gas and Energy.

And if this is true, would it be safe to say that energy can be converted to matter?

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the fourth state is plasma, not energy.
energy is not mass, mass can be converted to energy.

Energy can be converted to mass.

Based on Einsteins theory, e=mc2, would it be right to say that matter has 4 states?Solid, Liquid, Gas and Energy.And if this is true, would it be safe to say that energy can be converted to matter?
The fourth state of matter is plasma (ionised gas). And yes, energy can be turned into matter. For example in a process called 'pair production' a gamma ray (high energy photons) transforms into an electron + a positron (mass).
The upshot of this mass/energy correspondence is that conservation of energy is generalised to conservation of mass-energy.

mgb_phys
Homework Helper
I've never been happy with the 4 states of matter arguement.
Especially when you start adding special cases, is a bose condensate a new state? If so is a superfluid liquid different from a liquid, is a glass a different state, what about a plasma in a magnetic field.

I think it's more usefull to think of a tree.
At the top you have a split energy / matter
Then under matter you have branches for solid, liquid, gas.
Then under gas you have atomic, plasma
Under solid, different crystal states, liquid crystals, superconductors etc

Water is a liquid. A brick is a solid.

Now if I took a huge amount of bricks and observed them from a large enough distance, would the bricks not have liquid like properties? Say if we couldn't actually make out the individual bricks. How do we define the 4 states of matter?

Water is a liquid. A brick is a solid.

Now if I took a huge amount of bricks and observed them from a large enough distance, would the bricks not have liquid like properties? Say if we couldn't actually make out the individual bricks. How do we define the 4 states of matter?
Fluid properties, absolutely.

Water is a liquid. A brick is a solid.

Now if I took a huge amount of bricks and observed them from a large enough distance, would the bricks not have liquid like properties? Say if we couldn't actually make out the individual bricks. How do we define the 4 states of matter?
I believe the states of matter are defined by some deduction of the fact that a substance, when changing states, maintains a constant temperature. Or/also, it might have to do with chemical bonds between the constituent atoms.

There are significantly more than 4 states of matter. What about things like Bose-Einstein Condenstates, Superfluid, Quark-Gluon Soups and Liquid Crystal?

Water is a liquid. A brick is a solid.Now if I took a huge amount of bricks and observed them from a large enough distance, would the bricks not have liquid like properties? Say if we couldn't actually make out the individual bricks.
I don't think so Mayday. A fluid is defined as a substance that cannot withstand a shearing stress, i.e., it starts to flow when subjected to one. This would not apply to a collection of bricks, regardless of how far away you viewed it from.

I don't think so Mayday. A fluid is defined as a substance that cannot withstand a shearing stress, i.e., it starts to flow when subjected to one. This would not apply to a collection of bricks, regardless of how far away you viewed it from.
Precisely, a fluid is a substance that flows continuously when a shear force is applied. It is safe to say there are four primary states matter can take. Their defining properties are very specific.

_Mayday_: Then your observations would simply be incorrect. A better example would be the Earth's crust (solid) that does deform over protracted periods of time which causes earthquakes, mass wasting, etc. When you change the parameters, you can observe one state of matter acting like another. The definitions, I believe, include a short or perhaps instantanous observation of the material.

Whats the difference between a molecule and a brick? I agree with mayday, from far enough away a collection of bricks would act like a liquid. The collection floating in space couldn't withstand a sheer stress. Each individually could, so could a molecule of sugar.

Whats the difference between a molecule and a brick? I agree with mayday, from far enough away a collection of bricks would act like a liquid. The collection floating in space couldn't withstand a sheer stress. Each individually could, so could a molecule of sugar.
You're comparing apples to oranges. A brick is a solid which displays macroscopic properties of solid state. You could put anything in space and do whatever you want with it, but in this case you'd just be experimenting with Newton's Laws. It would not act like a liquid. The rigid bricks would just move, not flow or deform.

mgb_phys
Homework Helper
It depends on your choice of scale.
A grain of wheat is a solid, wheat flowing down a pipe into a tanker behaves like a liquid the dust it throws up is a solid but behaves like a gas.

Timescale also plays a part, a tank shell hitting armour behaves like a liquid, even though it hasn't melted.

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LURCH
the fourth state is plasma, not energy.
energy is not mass, mass can be converted to energy.
I have found it more helpfull to think of matter and energy as the two forms of mass. Matter can be converted to energy, or energy to matter, of equal mass.

I've never been happy with the 4 states of matter arguement.
Especially when you start adding special cases, is a bose condensate a new state? If so is a superfluid liquid different from a liquid, is a glass a different state, what about a plasma in a magnetic field.

I think it's more usefull to think of a tree.
At the top you have a split energy / matter
Then under matter you have branches for solid, liquid, gas.
Then under gas you have atomic, plasma
Under solid, different crystal states, liquid crystals, superconductors etc
I absolutely agree.

"States of matter" are only useful labels for practical talking. They aren't really separated categories.

It's enough to take water and notice that the boundary between liquid and vapor is a hard boundary only below a certain critical pressure. For higher pressures, there is a soft transition from liquid to gas and viceversa, and therefore a region where you cannot really say if it's more liquid or more gas.

It's just not very easy to define what really is solid, liquid and gas, other than to base the definitions on practical experience.

Everyone has a practical image that a solid would keep its shape, but that's not technically true. An amorphous solid (e.g. glass, clay, a whole planet) certainly doesn't keep its shape forever. Lots of substances have more than one solid state (e.g. carbon = diamond & graphite) with so many different properties compared to each other that they have practical differences as big as from being liquid.

dst
You're comparing apples to oranges. A brick is a solid which displays macroscopic properties of solid state. You could put anything in space and do whatever you want with it, but in this case you'd just be experimenting with Newton's Laws. It would not act like a liquid. The rigid bricks would just move, not flow or deform.

If we're talking something on the order of 10^10 bricks or however many bricks it takes to compare with the number of H2O molecules in a glass of water, then we'd surely expect to see some form of liquid motion. Disregarding gravitational effects, of course.

" It depends on your choice of scale.
A grain of wheat is a solid, wheat flowing down a pipe into a tanker behaves like a liquid the dust it throws up is a solid but behaves like a gas.

Timescale also plays a part, a tank shell hitting armour behaves like a liquid, even though it hasn't melted."

However, something like a stack of bricks would not have inter-particle attraction and thus, I would think, not be able to sustain things like surface tension and turbulent flow.

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