Chemistry Reference
In-Depth Information
The Water Displacement Method
Empty graduated
cylinder.
Graduate is filled with
known amount of water.
Water rises by a volume
that is equal to the
volume of the object.
Figure 2-2a
Measuring the volume of a gas is a bit different, because a gas will take
on the size of the container you put it in. This means that if you measure a
gas in a 2.0 L bottle, the volume of the gas will be 2.0 L, but if you put the
same sample in a 5.0 L bottle, the volume of the gas will be 5.0 L! As you
will learn in Chapter 8, the volume of a gas doesn't tell us much, unless we
also know the temperature of the gas and the pressure it exerts.
In Lesson 2-1 I told you that the liter is an outdated unit, but the truth is
that it continues to be useful in chemistry class. In your laboratory, you can
find graduated cylinders, beakers, and flasks that measure volume in liters
and milliliters. To convert between the liter and the more accepted units of
cubed lengths, try to commit the following conversion factors to memory.
Important Conversion Factors for Volume
1 ml = 1 cm
3
1 L = 1 dm
3
1000 cm
3
= 1 dm
3
1000 ml = 1 L
Another very important property to be able to measure in the chemis-
try laboratory is mass. Mass is a measure of the amount of matter that an
object contains. In a sense, measuring the mass of an object is akin to de-
tecting how many atoms are in it, because we can calculate the number of
atoms in a pure sample when we know its mass. Mass and volume are often
confused, because mass takes on another meaning in English. When you
see something that is large, you might say, “That is massive!” In chemistry,
however, mass has nothing to do with the size of an object. If you see a
large object in chemistry, you should say, “That has a large volume!”
In the chemistry laboratory, you will be using an instrument called a
balance to measure the mass of various materials. These balances are
sometimes incorrectly referred to as “scales.” Sometimes, the process of
