# Question about the states of matter

• B
I have a question, and it is this: why is it that your hand can go through a gas or liquid while the same can't be done with solids? Is it because of density?

ProfuselyQuarky
Gold Member
Indeed, it has to do with density. Do you know the difference between how atoms are arranged in the different states of matter?

Indeed, it has to do with density. Do you know the difference between how atoms are arranged in the different states of matter?

Kind of. I believe I do in a way.

ProfuselyQuarky
Gold Member
See the image http://www.msm.cam.ac.uk/SeeK/slg.html [Broken]?

The atoms are closely packed together in the solid, but they become increasingly spread apart for the liquid and gas. There is more space between the atoms in the two latter states.

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See the image http://www.msm.cam.ac.uk/SeeK/slg.html [Broken]?

The atoms are closely packed together in the solid, but they become increasingly spread apart for the liquid and gas. There is more space between the atoms in the two latter states.

Yeah, I actually did know that, but thanks, anyway.

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ProfuselyQuarky
Gold Member
So if you knew that, what exactly were you asking? You could clarify and then I could help you better

So if you knew that, what exactly were you asking? You could clarify and then I could help you better

I just wasn't completely sure about it.

ProfuselyQuarky
Gold Member
Okay, then. Now you're sure :)

jbriggs444
Homework Helper
The density of a substance has quite little to do with whether you can move your hand through it.

You can push your hand through liquid water more easily than you can push your hand through a cube of expanded polystyrene (styrofoam). What matters is not so much how dense the material is, but how firmly the component molecules are bound into a matrix.

The density of a substance has quite little to do with whether you can move your hand through it.

You can push your hand through liquid water more easily than you can push your hand through a cube of expanded polystyrene (styrofoam). What matters is not so much how dense the material is, but how firmly the component molecules are bound into a matrix.

You mean as in how tightly packed they are, right?

jbriggs444
Homework Helper
You mean as in how tightly packed they are, right?
More like how inflexible the packing arrangement.

olgerm
Khashishi
It's not just density. Water is denser than ice, you know. In a solid, all the molecules are bound together in an orderly formation, so you have to break many bonds to move your hand through. In a liquid, the molecules stick together but aren't in a tight formation. The molecules are all disorganized. So, when you push your hand through, the molecules can bend shift around relatively freely.

ProfuselyQuarky
Gold Member
So, when you push your hand through, the molecules can bend shift around relatively freely.
In other words, the space between molecules can change.

jbriggs444
Homework Helper
In other words, the space between molecules can change.
No. The arrangement of the molecules can change. The [average] space between them need not change.

ProfuselyQuarky
Gold Member
No. The arrangement of the molecules can change. The [average] space between them need not change.
But it can. That's all I was saying.

Khashishi
I don't know if the difference between a liquid and solid is totally cut and dry. There's not a whole lot of difference between a very high viscosity liquid and and amorphous solid. Practically speaking, solids won't flow, but ductile metals can be pressed into shape with enough force.

ProfuselyQuarky
Gold Member
I don't know if the difference between a liquid and solid is totally cut and dry. There's not a whole lot of difference between a very high viscosity liquid and and amorphous solid. Practically speaking, solids won't flow, but ductile metals can be pressed into shape with enough force.
That is something I often wonder. Like, is lotion a solid or liquid? A semi-liquid? A semi-solid?

jbriggs444
Homework Helper
But it can. That's all I was saying.
In a liquid, the average space between molecules does not change. And yet liquids flow. In a solid, the average space between molecules does not change. But solids do not flow [much]. The average spacing between molecules can not be the determining feature. That is what I am trying to point out.

ProfuselyQuarky
ProfuselyQuarky
Gold Member
In a liquid, the average space between molecules does not change. And yet liquids flow. In a solid, the average space between molecules does not change. But solids does not flow [much]. The average spacing between molecules can not be the determining feature. That is what I am trying to point out.
Fair enough.