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Got a AS Geology essay titled [b]"Referencing to examples, explain how the physical properties of minerals may be related to their internal structure."[/b]
Using graphite and diamond as examples as they are allotropes. By physical properties, it means Hardness, Cleavage (planes of weakness), Colour, Lustre (how it reflects light), Specific Gravity (approximation of weight) and shape of their crystals.
I can do hardness, cleavage and crystal shape easy, I just can't think of how a diamond having an Isometric-hexoctahedral structure would effect it's colour or Lustre? I suppose this is Chemistry, and help appreciated :/
This absolutely is chemistry - it's all to do with crystal structures.
Specific gravity (which in other words is density) varies between different crystal structures due to their packing - if it's more tightly packed, you get more atoms in the same space and a greater density.
Colour - I would imagine this is because in diamonds, each carbon atom sits in a tetrahedral hole - it's connected to 4 other carbon atoms. It therefore doesn't have any electrons free. This means it's non-conductive and means there's nothing to adsorb any light (causing it to have a colour) - I'd also not expect the C-C bonds to adsorb at any wavelength because they're pretty rigid due to the crystal structure.
Thanks a lot, I'm doing AS Physics and Chemistry too, but since we're just starting I haven't done any of this.
Teacher is being a bit of a dick, setting a question we shouldn't really know how to answer and "seeing how we deal with it". I've done better than most of the class though and actually managed to work out what the question is after xD
[QUOTE=Mort and Charon;32273546]Thanks a lot, I'm doing AS Physics and Chemistry too, but since we're just starting I haven't done any of this.
Teacher is being a bit of a dick, setting a question we shouldn't really know how to answer and "seeing how we deal with it". I've done better than most of the class though and actually managed to work out what the question is after xD[/QUOTE]
i only started crystal structures and lattices in 2nd year undergraduate chemistry so I wouldn't worry too much
Well, I'm guessing diamonds would be shinier because there would be less atoms at the surface, meaning that each surface atom will get more photons (that aren't capable of raising its energy level) and therefore will reflect more. The others, since they're tucked inside the structure, they have a higher chance of releasing their photons on other atoms.
The color...well, I guess the structure of graphite has less possible clear paths for a photon to pass through, making it darker.
Any logic to this?
I'm thinking for Lustre (shiny-ness) and crystal habit (how well formed the crystals are), the fact that diamond has such a strong structure creates such a smooth shiny surface and euhedral habit. Whereas the weakness in the inter-molecular bonds(are they these?) in graphite's structure creates the anhedral granular habit, and therefore lack of shiny-ness.
[editline]13th September 2011[/editline]
It's not hugely important I get this 100% correct, but it would help a lot if it I was mostly right.
But you'd expect the diamond to be more rugged since it's harder to polish by erosion.
Well since it is formed under such high pressure, and mostly contains no impurities, it is smooth in the first place. Plus a rough, uncut diamond is obviously no where near as shiny/clear as in its cut state.
And hey, man, graphite s composed purely out of carbon. So, the bonds would be atomic, not molecular, right?
graphite is a semi-metal, so it's partially metallic bonds, and partially covalent bonds
Carbon atoms in graphite only have covalent bonds with 3 other atoms, rather than four in diamond. They are arranged in a hexagonal mesh, in layers, and these layers are joined by molecular bonds rather than atomic/covalent. That's why graphite is so soft and is used as a lubricant, the layers slide over each other easily.
I think, I haven't taken chemistry in 2 years
[editline]13th September 2011[/editline]
I hope*
[editline]13th September 2011[/editline]
oh ok I guess not.
Speaking of which, why does a whole bunch of carbon turn into graphite and not diamond?
And another thing, if diamond requires such hardcore pressure to form, why doesn't it simply turn back when the pressure stops being applied? The same with chemicals that are only synthesized in extreme heat and such.
it's like throwing a ball into a cup sitting on the shelf.
It takes a lot of energy to get it up there, but once it's up there, it's not going anywhere.
However, it is slightly less stable when it's sitting there on the shelf, so it only takes a tiny bit of activation energy to knock it over.
Would the free electrons/conductivity in graphite have anything to do with giving it a metallic/sub-metallic lustre?
[QUOTE=Mort and Charon;32286911]Would the free electrons/conductivity in graphite have anything to do with giving it a metallic/sub-metallic lustre?[/QUOTE]
Yup.
According to band theory, as the molecular orbitals within the valence bond are abundant and close enough, electrons can absorb and release photons.
Here's a fairly crude diagram that gives you an idea of what happens.
[img]http://4.bp.blogspot.com/_R4bDDgSUj2g/R5aXw0QQ89I/AAAAAAAACts/obiir8K40Ss/s400/photon_absorption_large.jpg[/img]
Or just good old fashioned photoelectric effect.
The valence shell model is very outdated though
Thanks, but I'm not too knowledgeable with photons and all that, and that's probably a bit too indepth for a basic geological essay xD
Hey guys, I was just wondering if you know of any tips or tricks for taking notes in Word?
It's a pain in the Biology classes because we do so many drawings on the board that I can't put on my virtual notes, so I would appreciate any suggestions! :)
[QUOTE=Jo The Shmo;32308838]The valence shell model is very outdated though[/QUOTE]
Yeah, hence the crude. But it's sufficient.
[QUOTE=Cree8ive;32316230]Hey guys, I was just wondering if you know of any tips or tricks for taking notes in Word?
It's a pain in the Biology classes because we do so many drawings on the board that I can't put on my virtual notes, so I would appreciate any suggestions! :)[/QUOTE]
buy a pad of paper and a pen. take notes in the conventional way.
if it really kills you and you HAVE to do it virtually, you can either
1: take notes the normal way, copy them up into word later, scanning in the diagrams - this will at least help you learn it more by copying it
2: take notes in word as you go along, make diagrams on paper, combine the two later.
personally, i don't see the point of making notes on a computer. i've never done it, and nobody i know has.
especially in science based courses, trying to do it on a computer is going to be a nightmare. while it probably eases organisation of notes (in some of my quantum theory lectures during my degree, i was taking down around 10 pages of notes and equations), the limitations of doing it digitally just aren't worth it.
a paper and pen are lighter and cheaper than a laptop and don't run out of battery either.
Thanks for replying mike.
That's what I'm currently doing now in class, taking the notes on the computer and drawing the drawings in my textbook, but everything isn't bunched together so I was just wondering if there was something specialized for this purpose.
I guess I'll keep to the system I got right now. :)
[QUOTE=Cree8ive;32317182]Thanks for replying mike.
That's what I'm currently doing now in class, taking the notes on the computer and drawing the drawings in my textbook, but everything isn't bunched together so I was just wondering if there was something specialized for this purpose.
I guess I'll keep to the system I got right now. :)[/QUOTE]
the only real solution if you wanted it all on computer would be to use a computer with a touchscreen and something like onenote - not really worth it though
Use paint, brah.
Nothing beats pen, pencil and a fuck load of highlighters.
[QUOTE=Mort and Charon;32320071]Nothing beats pen, pencil and a fuck load of highlighters.[/QUOTE]
True, although I need to get a new notebook for that (not as in computer notebook).
I was just thinking, if you shine a light through a piece of glass the light is absorbed and remitted by atoms throughout the glass, right? Why exactly do the photons retain their properties (or information)?
Like let's say I shine polarised light through a window pane: the light will remain polarised once it's passed through the glass... but how? How is this information retained and not lost through electron excitement and remission?
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