SOLID, LIQUID, OR GAS?225SCIENCELIQUID STATE
The atoms or molecules in a liquid
substance can slide over each other,
so a liquid can be poured into a
container. But the electrical forces
between the atoms or molecules in a
liquid stop them from pulling apart.
GASEOUS STATE
The electrical forces between the atoms
and molecules in a gaseous substance have
broken down completely, so they will fill
the container in which they are held. Gases
cannot be poured like liquids, and many,
but not all, are invisible.CHANGING STATES
If you heat a solid enough, the atoms or
molecules from which it is made get enough
energy to break apart and slide over each
other. The solid melts and changes from
the solid state into the liquid state.
Heat the liquid further, and it boils,
changing into the gaseous state.
OSome substances, such as iodine, can
change directly from a solid to a gas
without first becoming a liquid. This
is called sublimation.
OAt room temperature, dry ice
(frozen carbon dioxide) sublimes to
become carbon dioxide gas.Condensation
GAS TO LIQUID When water vapor in
the air loses energy, the molecules stick
together and become liquid water.Liquid metal At room temperature,
nearly all metals are solids. But there
is one exception—mercury. Mercury has
a melting point of –36.4°F (–38°C), so it
stays liquid—even if you put it in a freezer.
Heating up Solid aluminum reacts with
liquid bromine to give solid aluminum
bromide. The reaction produces a lot of
heat, and the excess bromine boils. This
produces brown fumes of bromine gas.LIQUID TO GAS If you heat liquid water up
to its boiling point, 212°F (100°C), the molecules
evaporate (turn into a gas) and escape into the air. Evaporation
GAS The atoms or
molecules in a gas are
held so loosely that they
fly away into space.INTO THIN AIR