226Mixing chemicals
A few common substances are made of just one chemical, such as
pure water or pure salt. Most of the things that we come across
every day, however, are combinations of several chemicals.
COMPOUNDS
Many substances undergo changes
when they are mixed together.
The chemical bonds that bind the
molecules to each other break apart
and then recombine to form new
substances called compounds. DISHWASHING
LIQUID is a mixture
of soap, water, and
other chemicals. OIL AND WATER
never combine because
their molecules repel
each other.TAKE A LOOK
COARSE
MIXTURE In some
mixtures the particles
are large enough to
be seen and separated
easily. Gravel is a
coarse mixture.OMixtures are made of different
elements or molecules. During
mixing, some of the substances
may become harder to see. In
coarse mixtures you can usually
spot each substance. Suspensions
may look like a single liquid, but
eventually they separate out.
Solutions are the most thoroughly
mixed—it is often difficult to tell
there is more than one substance. SUSPENSION
When small soil
particles are mixed
with water they form a
suspension. Eventually
the heavier solids will
sink to the bottom. SOLUTION When
one substance dissolves
in another it is called a
solution. Seawater is a
solution of salt and
water; air is a solution
of gases.MIXTURES
Some substances do not
react when they are added
together because they
cannot form chemical
bonds. These are called
mixtures. Mixtures can
easily be separated again
because the original
substances do not change. COLLOID These
are like suspensions,
but the particles do
not sink to the bottom.
In milk, tiny droplets
of fat float in a
watery solution.SCIENCE