Chemistry Reference
In-Depth Information
such as water (H
2
O) and carbon dioxide (CO
2
), are called binary compounds.
Compounds that contain three elements, such as glucose (C
6
H
12
O
6
), are
called ternary compounds.
Whereas a compound is made from the chemical combination of two
or more substances, a mixture is made from two or more substances that
are physically combined. You don't need a chemical reaction to make a
mixture, nor do you need one to separate a mixture. If you had a handful of
copper coins and a handful of silver coins, and you mixed them together in
a purse, you would have a mixture. Notice that, unlike in the example of
compounds, the substances that make up a mixture do not lose their indi-
vidual properties. The copper coins don't stop being copper coins just be-
cause they are physically combined with silver ones.
There are many different types of mixtures, but they all have these
common characteristics: They represent physical combinations of two or
more substances. The individual substances in a mixture do not lose their
original properties, and the substances in a mixture can be separated by
physical means. Another characteristic that all mixtures share is that their
composition is variable. By this I mean that the substances that are found in
the mixture can be mixed in with varying proportions or concentrations. If
you mixed in five silver coins and three copper coins, or four silver coins and
seven copper coins, you still end up with a mixture of copper and silver coins.
Heterogeneous mixtures are mixtures that do not have a consistent, or
uniform, composition throughout the entire sample. A good example of
this would be chicken soup. When you make chicken soup, the denser ma-
terials will sink to the bottom. If you scoop out soup to fill two bowls, it will
make a difference from which area of the pot you take from. If you take a
scoop from near the surface of the pot you will end up with mostly broth
and the less dense items that float, such as pasta. If you take from the bot-
tom of the pot, you will end up with more of the dense items, such as chicken
and carrots. No two samples taken from the same pot will be all that simi-
lar, because this type of mixture is not uniform. Other examples of hetero-
geneous mixtures include a bowl of mixed nuts, a handful of sand, a
chocolate chip cookie, and a scoop of rocky road ice cream.
Unlike heterogeneous mixtures, homogeneous mixtures do have a uni-
form composition. By this I mean that the composition of an entire sample
is consistent. If you were to take one scoop out of one area of a homog-
enous mixture and a second scoop out of a different area of the same sample,
the composition of each scoop would be essentially the same.
