Assignment 2, Fall 2008. A Virtual Museum Tour
The aims of this homework are to introduce you to several inorganic materials, both metallic and
ceramic; including copper and copper oxide. The assignment will also re-acquaint you with an
on-line search; we will be using the world-wide-web as a virtual museum. Some basic definitions
and terms are also introduced; these are important! The answers to all the following questions
can be obtained online. Good places to start, for information on elemental materials are:
Wikipedia: The Free Enclopedia at: http://en.wikipedia.org/wiki/Main_Page
WebElements at: http://www.webelements.com/
ELEMENTS, NATIVE ELEMENTS, METALS AND NON-METALS
element, n. :
substance/material composed of atoms which are chemically alike; A basic unit
which cannot be resolved into simpler parts by a chemical reaction.
native element, n. : found pure in nature; in a natural state; not chemically bonded as in a
compound.
metal, n. :
any one, or a combination thereof, of elements such as gold (Au), silver (Ag),
copper (Cu). Metals have a lustrous appearance, and are good conductors of
heat and electricity. Metals tend to be ductile and malleable.
non-metal, n. :
a substance/material that lacks the properties of a metal. Carbon
(C), nitrogen (N), and oxygen (O) are typical non-metals .
non-metallic, elemental solid, n. : a non-metallic element that is solid at room temperature
and pressure. Carbon, in the form of Diamond or Graphite, is a non-metallic,
elemental solid; nitrogen and oxygen are not!
Certain metals, and indeed non-metals, which were used in antiquity, and are still used
extensively today, are “native”, i.e., they can be found in their natural state, and are not
chemically bonded to other elements. Perhaps the classic example is gold (Au) which has been
used for at least eight thousand years! Gold is found in its elemental form as grains in quartz or
as placer deposits in alluvial beds etc. Copper (Cu) veins and seams were found worldwide, and
the extensive deposits in the Upper Peninsula of Michigan were traded throughout the preColumbian Americas, and used for tools, weapons and ornamentation.
When in their native state, both metals and non-metallic elemental solids are classified as
minerals.
Minerals, n. : materials obtained by mining, drilling or digging in the earth. Minerals are
inorganic (non-carbonaceous), are naturally occurring, crystalline and of a
definite composition.
Hence:
(i) native Cu is both a metal and a mineral;
(ii) naturally deposited sulfur (S) is both a non-metallic, elemental solid and a mineral.
However if Cu is extracted or smelted from e.g., Cuprite (Cu2O), the resultant Cu is no longer a
mineral but is a metal and an engineered material.*
METALS AND CERAMICS
ceramic, n. :
from keramos (burnt earth). Historically referred to oxides. Now includes all
inorganic, non-metallic compounds (e.g., sulfides and carbides) and nonmetallic, elemental solids (e.g., carbon). Traditional ceramics include pottery,
earthenware and porcelain. Ceramics are Engineered Solids.
compound, n. : material formed by the chemical combination of two or more elements. {Latin
com (together) + ponere (put)}
oxide, n. :
compound of oxygen with another element, typically a metal.
Iron (Fe) is a metal. However, the compound Fe2O3 (hematite) is an oxide ceramic*. It has very
different properties as compared with its parent metal (Fe). In the following, we shall compare
the properties of ceramic oxides, with those of the associated metal. We shall use Specific
Gravity (SG) and Hardness (H) as property indicators.
Table 1
Mohs' Hardness Scale
1. Talc
2. Gypsum
3. Calcite
4. Fluorite
5. Apatite
6. Orthoclase
7. Quartz
8. Topaz
9. Corundum
10. Diamond.
Specific gravity, n. : the ratio of the weight of a given substance to that of an equal volume of
water: the mass per unit volume when the specific gravity of water, at 4˚C, is
taken to be 1. Hence specific gravity and density are often numerically equivalent.
Hardness, n: the comparative ability of one substance to scratch or be scratched by another
substance: a relative measure of the "strength" or resistance to deformation of a
substance.
*
*
Certain definitions which are used in the text can also be found in the course book.
Hematite (Fe2O3 ) can be classified as either a ceramic (engineered solid) or as a mineral (naturally occurring).
Around 1850, Freidrich Mohs proposed a scale of hardness from 1-10, with diamond, the hardest
material, assigned a value of 10, and talc the softest material, a value of 1. Mohs' scale is
reproduced in Table 2. Note that Mohs used minerals (naturally occurring, crystalline materials)
to develop his seemingly primitive, but oft used, (and indeed remarkably useful) scale of
hardness.
CRYSTAL STRUCTURES AND OXIDE CERAMICS/MINERALS
crystal, n: a solid within which the atoms or monomers are arranged in a regularly repeating
network or lattice of points in space. In a crystal, the interatomic distances are fixed. A less
rigid definition of a crystal is “a clear transparent mineral that looks like ice” (Greek krystallos,
clear ice).
crystal structure, n: the periodic arrangement of atoms or molecules in space; the crystal
structure may be described in terms of the shape of the lattice
Most solid materials; metals, ceramics and by definition all minerals, are crystalline, i.e., the
constituent atoms decorate a perfectly repeating lattice. Certain materials display macroscopic,
morphological characteristics (e.g., faceting) which are a reflection of the internal arrangement
and symmetry of this lattice. All crystals may be assigned to one of seven crystal systems, based
on the shape of the lattice. These are: cubic (also called isometric), tetragonal, hexagonal,
orthorhombic, trigonal (also called rhombohedral), monoclinic, and triclinic. (Do not worry
about remembering these names!)
Table 2
Properties of Metals and their Associated Oxides
Mineral/
Ceramic
Name
Hematite
Fe2O3
Specific
Gravity
of the
Oxide
4.9-5.3
Mohs’
Crystal
Hardness Structure of
of Oxide Oxide
5.5-6.5
Ore for
Which
Metal?
Hexagonal/
Iron
Rhombohedral Fe
Specific
Gravity
of the
Metal
7.0-8.0
Mohs’
Crystal
Native
Hardness Structure Metal
of Metal of Metal
(Y or
N)
4.0-5.0
Cubic/
Y
Isometric
Cuprite
Cu2O
Copper
Cu
Y
Cassiterite
SnO2
Tin
Sn
Y
Rutile
TiO2
Titanium
Ti
Y
Alumina
Al2O3
Aluminum
Al
N
Uraninite
UO2
Uranium
U
N
Questions 1-30
Fill in the 30 blanks in Table 2 (6 are filled in for you), which lists structure/property data for the
oxide ceramics that may also be used as ores for various metallic elements. As an example, an
oxide of iron, hematite, is identified in terms of its composition (Fe2O3), its Mohs’ hardness, and
its Specific Gravity. Hematite is an iron ore, and iron itself can be found as a native element:
hence the yes (Y), in the last column.
When you have filled in the Table, go to the Lesson 02 Assignment folder on ANGEL, and use
the data in Table 2 to answer the quiz questions. In certain cases, the range of values will
encompass more than one answer range (a sample ANGEL quiz question is shown in Table 3).
In such cases, choose one of the ranges, and credit will be given. For example, the Mohs’
hardness of hematite varies from 5.5 to 6.5, which spans two numerical ranges, 5.0 to 6.0, and
6.0 to 7.0. If you choose either of these answers, E or F, you will receive full credit.
Table 3
Sample ANGEL Quiz Question
1.
The Mohs' hardness of Hematite is approximately
A.
B.
C.
D.
E.
F.
G.
H.
I.
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
SUMMARY
When you have read through this assignment, you should find that all crystalline, inorganic solid
materials can be classified according to some simple rules.
(i)
(ii)
(iii)
(iv)
(v)
(vi)
If that crystalline, inorganic solid is naturally occurring, it is a mineral.
Minerals are either metallic or non-metallic.
Non-metallic minerals include non-metallic, elemental solids and compounds (e.g.,
oxides and sulfides).
If minerals are elemental (not compounds), they are termed native.
Materials which are inorganic, and are processed by man (engineered materials) are
either metals or ceramics.
Ceramics include non-metallic, elemental solids and compounds (e.g., oxides and
sulfides).
During the semester, we shall encounter other solid materials. For example, glasses are noncrystalline, they are amorphous; but can be “metallic” or “ceramic”. Organic materials include
polymers!