Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: DoctorBeaver on 13/08/2008 23:04:06

Title: What determines weight?
Post by: DoctorBeaver on 13/08/2008 23:04:06

Iron is a lot heavier than, say, lithium. But what determines its weight? Is it purely the number or nucleons, or does how closely packed the atoms are also have a bearing?

Title: What determines weight?
Post by: Make it Lady on 13/08/2008 23:16:32

I was led to believe it was down to a bit of each.

Title: What determines weight?
Post by: DoctorBeaver on 14/08/2008 08:37:34

Is either more important?

Title: What determines weight?
Post by: DonBrown on 14/08/2008 13:36:38

Which weighs more, a pound of lead or a pound of feathers?
Or if you prefer, a kg of Li or a kg of Fe?

Title: What determines weight?
Post by: DoctorBeaver on 14/08/2008 13:53:29

Don - that's not what I was getting at. 1cm³ of Fe would weigh a lot more than the same amount of Li.

Title: What determines weight?
Post by: lightarrow on 14/08/2008 14:28:42

Quote from: DoctorBeaver on 13/08/2008 23:04:06

Iron is a lot heavier than, say, lithium. But what determines its weight? Is it purely the number or nucleons, or does how closely packed the atoms are also have a bearing?

With a few exceptions, metals are all packed in the maximum way, so what is left is every atom's density which in turn, generally, increases with the number of nucleons (down a group)

Title: What determines weight?
Post by: DoctorBeaver on 14/08/2008 17:24:47

Thank you, Alberto.

Title: What determines weight?
Post by: Make it Lady on 14/08/2008 17:43:02

But then we have non-metals with diverse structures and compounds. What about sunflower oil and honey. One floats on the other. Packing definitely has an affect here.

Title: What determines weight?
Post by: Bored chemist on 14/08/2008 19:12:39

The atoms in lead are roughly twice the mass of the atoms in silver, yet the densities of the metals are roughly the same. I think they are both fairly nearly close packed structures. The difference in this case is the size of the electron cloud around the atoms.

Incidentally quite a lot of the atoms in honey are oxygen, relatively few of the atoms in sunflower oil are, and oxygen is the heaviest atom in either of the 2 compounds.