Chemistry Reference
In-Depth Information
TEXTBOX
4
THE PROPERTIES OF MATTER
All substances - elements as well as compounds - have characteristic and
distinctive
chemical
and
physical properties
(see Table 5). The
chemical
properties
are related to the changes in composition that substances
undergo when interacting with one another. A chemical property of solid
iron, a metal, for example, is that it interacts at ambient temperature with
atmospheric oxygen, forming iron oxide, a dark brown material commonly
known as
rust
. Copper, another metal, interacts at ambient temperature
not only with oxygen but also with atmospheric moisture and carbon
dioxide, forming copper carbonate, a green substance; copper carbonate,
which covers copper surfaces exposed to the environment, often forms, on
its outer surface, a layer of green “patina” on antique copper objects.
Whether a substance reacts (interacts) or does not react with others is also
a chemical property. A chemical property of gold, for example, is that it
does not react with the components of the atmosphere or the soil or, for
that matter, with practically any element or compound. Because of its low
chemical reactivity, gold is known as a
noble metal
. Another noble metal
is platinum.
TABLE 5
Properties of Substances
Physical properties
Color, refractive index, ductility, hardness, malleability,
melting point, boiling point, density, thermal
conductivity
Chemical properties
Composition; reactivity with other substances; stability
to heat, radiation, and electricity
The
physical properties
of substances do not involve chemical changes.
Color
(see Textbox 17) and
crystal structure
(see Textbox 21), for example,
are physical properties that are characteristic of a substance that serve to
identify most substances. Other physical properties, such as
density
,
hard-
ness
(see Table 3),
refractive index
(see Table 19), and
heat capacity
(see
Table 101), are also useful for characterizing and identifying substances as
well as distinguishing between different substances.
