Chemistry Reference
In-Depth Information
specific and characteristic temperature and pressure. When iron, a solid at
ambient temperature and pressure, is heated to a high temperature -
namely 1538°C - it melts, turning into a liquid; and at 2861°C it boils,
changing from a liquid to a gas.
Water
, on the other hand, the most abun-
dant substance on the surface of the earth, is solid only at very low tem-
peratures: ice (solid water) melts at 0°C and boils at 100°C. Because the
temperature range of the liquid state is very narrow (only 100 degrees),
water exists naturally on the surface of the planet in all three states, as
ice, liquid water, and a gas (water vapor).
The melting points of mixtures and solutions depend on the
nature and the relative amount of each component of the solution. They
are, however, lower than those of the separate components.
Solder
,
for example, an alloy of tin and lead, melts at 183°C, a much lower tem-
perature than either of its components: tin melts at 231°C and lead, at
328°C.
FIGURE 4
The states of matter.
All matter - whether solid, liquid, or gaseous
- is made up of atoms or molecules. The amount of energy of the atoms or mol-
ecules differs in each one the three states. In solids they have little energy; are
tightly packed (usually in a regular pattern) and retain definite shapes. In liquids
they have more energy than in solids, are closely packed together, but are not
regularly arranged, sliding past each other; consequently, liquids keep no regular
shape and acquire the shape of their container. The atoms or molecules of gases
have much energy, move rapidly, are well separated from each other, and retain
neither a regular arrangement nor a definite shape.
