Properties of materials: more than physical and chemical 1

These aren’t really ‘properties’ – more like
definitions that relate to what’s happening
microscopically. The goal here is to relate
structure to properties.
The kinds and relative count of elements, ions or
other constituents in a material; chemical formula,
percent in an alloy, etc. Note that a single
composition can have different structures, for
instance allotropes of sulfur or polymorphs in ironcarbon systems. The basic starting point is:
metallic elements
metals + nonmetals
ionic &
carbon, hydrogen
Atomic scale order; the manner in which
atoms or ions are spatially arranged. It is
defined in terms of unit cell geometry. A
material with long-range order is called
crystalline (contrasted with amorphous).
The structural features that can be seen
using a microscope, but seldom with the
naked eye; ranges from glassy to crystalline;
includes grain boundaries and phase
These are the standard properties that we
teach in chemistry class.
Solid, liquid or gas; not as simple as it may
Mass of a material per unit volume. Low
density, high strength materials are desirable
for manufacturing aircraft and sporting
The physical attraction for iron, inherent in a
material or induced by moving electric
fields. Iron, cobalt, nickel and gadolinium
are inherently ferromagnetic.
The maximum amount of a solute that can be
added to a solvent. Solubility is complex in
some solid materials, for instance the ones
that form eutectic mixtures; a good starting
point to discuss complex phase diagrams.
Resistance of a material (usually liquid) to
flow. Plastics and glasses become less viscous
with increasing temperature.
The concepts of stress, strain, elasticity,
deformation and failure are necessary to
understand and interpret mechanical
The ability of a material to be reshaped in all
directions (plastic deformation) without
failure; related to ductility and sometimes
called workability; an important
characteristic of metals.
The ability of a material to change shape
(deform) usually by stretching along its
length; closely related to tensile strength.
Strength is not a precisely defined
mechanical property, as there are many
types of strength. Collectively, it means the
ability of a material to stand up to forces
being applied without it bending, breaking,
shattering or deforming.
The resistance to being permanently
deformed or bent; measured by distance of
penetration into the material. There are
several scales used to measure hardness.
A characteristic of a material that relates to
its response to sudden blows or shocks.
Toughness can be expressed as the amount of
energy required for creating or propagating a
The absence of ductility; failure by sudden
fracture (no plastic deformation);
characteristic of ceramic materials.
The ability of a material to absorb force and
flex in different directions, returning to its
original position once the stress is removed.
Polymers are desirable for their elasticity.
For the sake of this summary, electricity is
defined as the flow of electrons.
A measure of how easily a material allows
electrical current to flow through. Metals
like copper, aluminum and iron have much
higher electrical conductivities than
ceramics, plastics, glass and rubber.
The reciprocal of electrical conductivity; a
measure of a material’s resistance to the
flow of electric current. Resistivity is an
important concept in semiconductors;
depends on electronic structure,
temperature and microstructure.
 Generally,
lack of reactive chemistry is
desirable for materials; this is a good place
to look through those MSD sheets.
A measure of a material’s ability to damage
or disrupt the metabolism of living tissue;
can be acute or chronic; can be administered
by contact, inhalation, ingestion, or
injection. The dose makes the poison.
Corrosion is an electrochemical process that
is closely related to the activity series. An
ion high on the list will replace a metal lower
on the list.
Mg > Al > Zn > Cr > Fe > Sn > Ni > Cu > Ag >
Corrosion is strongly dependent on
environmental variables.
A material’s ability to catch fire and burn;
important for organic materials and reactive
Use in or on the human body without
eliciting a rejection response from the
surrounding body tissues; includes materials
made of polymers, metals, ceramics, and
Think about heating a rod: it gets hot, it
expands, it conducts heat, it may soften or
The efficiency of a material in absorbing
heat. High specific heat means a material
heats fast and cools down fast. By definition,
the specific heat of a material is the energy
required to raise the temperature of 1 g of
that material by 1 °C.
Nearly all materials expand when heated and
contract when cooled. The extent to which
this happens is the coefficient of thermal
expansion. Bridges are designed with
expansion joints so they don’t buckle due to
thermal expansion.
Thermal conductivity is the rate at which
heat flows through a material. It depends on
the flow of both electrons and phonons.
The temperature at which liquid begins to
form as a material is heated. Not all
materials have distinct melting points, and
many materials have phase transition
temperatures in which crystal structure