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You can already tell it’s not experiment to find out which

balanced because the states each are in before you
number of oxygen atoms on complete this last step:
both sides isn’t the same. So
SnO 2 (s) + H 2 (g) Sn (s) +
we have an unbalanced
H 2O (g)
equation.

2. Balance the equation. Count
the number of atoms of each We’ll be practicing balancing
equations a lot during our
element on each side of the
chemistry experiments together, so
arrow. It’s easiest to start
you’ll be sure to get comfortable
with an element that appears
in only one of the reactants with these ideas.
and products. Use a pencil,
Properties of Gases
because it might take you a

few tries to get the numbers Pure substances all behave about
right. Write the numbers as the same when they are gases.
o
coefficients in front of each For example, at 0 C and 1
molecule. atmosphere of pressure, one mole
of gas occupies 22.4 liters of
I would start with tin (Sn),
volume. This nifty trick relies on
since it appears only once on
the fact that gases completely fill
each side. Notice that there
their containers, and the atoms of
is only one Sn atom on each
the gas are usually about 10
side, so Sn is balanced.
diameters apart. (This doesn’t
However, the oxygen (O) has
work with solids and liquids,
two on the left, but only one
however. ) The Ideal Gas Law
on the right. Here’s what I
relates temperature, pressure, and
came up with in the end:
volume of these gases in one
SnO 2 + 2H 2 Sn + 2H 2O simple statement:

PV = nRT where P = pressure, V =
3. Indicate the states of matter
volume, T = temperature, n =
in the reactants and
number of moles, and R is a
products. Use (g) for
constant. What I really want you to
gaseous, (s) for solids, (l) for
notice is how Pressure, volume,
liquids), (aq) for compounds
and temperature are related: when
in water. Sometimes you’ll
the pressure goes up, the
need a bit of help from an
temperature also goes up. When

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