Introductory
Chemistry
M
anychildrenplay with building blocks such as
Legos. They can combine blocks of different
shapes and colors to make almost any structure they
can imagine. For example, a child may build an airplane
and then may decide to take it apart and make a car, a
dinosaur, or even a model of the human body. An almost
infinite number of toys can be made using these basic
“building blocks.”
Nature also uses building blocks—they’re called
atom s.
Atoms vary in size and properties. They can
combine to make more complex structures called
m o l-
ecules,
which have different properties than their atomic
building blocks. Like a an airplane made out of blocks,
molecules can also be broken down. For example, your
body can break down the complex molecules in the fast
food meal you had for lunch into simpler ones that it ab-
sorbs. From these simpler molecules, it can build more
complex ones that it uses to make various structures,
such as parts of cells, tissues, and organs. It can also
string together many simple molecules to make more
complex ones that it will use to store
energy,
the ability
to do work. (If you eat too much fast food, the mol-
ecules may be stored as fat.) Finally, your body
can break down some simple molecules to
extract the stored energy. This is the chem-
istry of your body.
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