Density

[losfomot]

Can a material (or molecule) be denser than the elements that compose it?

 

I notice that the element Carbon has a density of 2.267, while diamond (which is Carbon) has a density of about 3.5

 

It occurs to me, though, that 2.267 could be an average density of the different forms of Carbon... is this so?

[swansont]

It's trivial if you can think of some gases that combine to form a solid or liquid at the same temperature. Like, maybe hydrogen and oxygen?

[losfomot]

It's trivial if you can think of some gases that combine to form a solid or liquid at the same temperature. Like, maybe hydrogen and oxygen?

 

That example does not make it seem so trivial...

 

H20 density = 1

 

H density = .09

 

O density = 1.43

 

I should have worded my question like so:

 

Can a material be denser than the densest element it is composed of ?

[insane_alien]

oxygen is denser than water? huh?

 

/me goes to look for water floating on pure oxygen.

[swansont]

oxygen is denser than water? huh?

 

Seconded.

 

<does math> Units, anyone? A mole of O₂ should take up about 22.4 L, so that's a density of 1.43g/L. The density of water is 1 g/mL, or 1 kg/L. There's a missing factor of 1000 in those numbers.

[RyanJ]

Wouldn't compressing the substance make it denser according too [math]\rho = \frac{m}{v}[/math]?

 

if so then that simply answers the question as yes, just compress the substance.

[insane_alien]

how about we use the densities at STP so we don't have to consider the effects of extreme pressures and alternate phases.

[swansont]

That's reasonable; I was assuming STP. The challenge will be something that's solid before and after, though I wouldn't be surprised if it/they existed. Starting with a gas and/or liquid is much easier.

[losfomot]

Seconded.

 

<does math> Units, anyone? A mole of O₂ should take up about 22.4 L, so that's a density of 1.43g/L. The density of water is 1 g/mL, or 1 kg/L. There's a missing factor of 1000 in those numbers.

 

 

Obviously O₂ gas is not denser that water.

 

I figured it might be the atomic density or some such craziness, but anyway, I got my initial figure of 1.43 g/cc here

 

Of course down below the list it says:

 

* Density of elements with boiling points below 0°C is given in g/l

 

Sorry, I shall try to double check things a bit better next time.

 

Anyway, so the answer to my original question would be yes.

 

That's reasonable; I was assuming STP. The challenge will be something that's solid before and after, though I wouldn't be surprised if it/they existed. Starting with a gas and/or liquid is much easier.

 

I did mean, and should have stated, STP.

 

What this all comes down to (for me) is this:

 

The densest element on the periodic table is Osmium... have we been able to make a molecule/compound/material denser than 22.6 g/cc? and if not, is it possible?

[swansont]

What this all comes down to (for me) is this:

 

The densest element on the periodic table is Osmium... have we been able to make a molecule/compound/material denser than 22.6 g/cc? and if not, is it possible?

 

That's much, much more restrictive. You'd need to have the compound have a structure where the change in bond length was a larger effect than any decrease in mass of the added element (if the second element is lighter) or vice-versa if the second element is heavier.

[Crooked Mick]

"I notice that the element Carbon has a density of 2.267, while diamond (which is Carbon) has a density of about 3.5"

 

More than likely what you have there is the density of graphite compared to the density of diamond. Both are pure carbon.

 

In graphite the atoms arrange themselves in hexagons very like honeycombs. Because of the geometry of electronic orbitals in this arrangement the honeycomb sheets are flat, and one sheet of honeycombs stacks on top of another. However the sheets do not come really close to each other because the electrons circulating freely about the sheets tend to repel each other. In this form carbon will conduct electricity quite easily and since the sheets slide over each other the material can be used as a lubricant. Graphite is a low density, low pressure form.

 

In diamond, the arrangement is different. Each carbon atom is arranged at the corners of a tetrahedron and is tightly bound to it's neighbours by four strong chemical bonds. This is caused by a different arrangement of the electronic orbitals which point toward the corners of a tetrahedron. Because of the tight bonding there are more atoms per cubic whatever of space and the density is higher. Also because of the tight chemical bonding, diamond is a poor conductor of electricity. Diamond is a high density, high pressure form of carbon and forms in high pressure environments such as deep in hot rocks.

 

Several pure elements can exist in different arrangements called allotropes. Carbon, tin, phosphorus, sulphur are just some of those that can.

 

Crooked Mick of the Speewah