Chapter 15 Laboratory: Thermochemistry and Calorimetry 269

Laboratory:

Thermochemistry and Calorimetry

Thermochemistry is the study of the heat evolved or absorbed during chemical reactions,

physical transformations (such as mixing), and phase changes (such as melting).

Calorimetry, from the Latin words calor for heat and metrum for measure, is a technique

used to measure the heat changes that occur in such processes.

All of the laboratories in this chapter require a calorimeter, a device that thermally

isolates the process being investigated, preventing gain or loss of heat from the external

environment. We used an inexpensive purpose-built calorimeter, which is available from

Home Science Tools (http://www.homesciencetools.com) and similar vendors for $15 or so.

If you don’t want to buy a formal calorimeter, you can achieve results nearly as accurate with

a home-built calorimeter. Both types of calorimeter are shown in Figure 15-1.

15

FIGURE 15-1: Store-bought (left) and homemade calorimeters

HERSUSATE v TEmpERATURE

Heat and temperature are related but not identical

concepts. A sample may contain a small amount of heat,

but the temperature may be relatively high, or vice versa.

For example, the sparks coming off a grinding wheel

are tiny particles of burning metal. Their temperature is

very high—perhaps 1,000°C or higher—but the particles

contain little heat, because the mass of each is a fraction

of a milligram. If one of those particles were to contact

your skin, you might not even notice it. Conversely, a

liter of boiling water is at a relatively low temperature,

only 100°C, but the kilogram mass of water stores a

considerable amount of heat. If that water comes into

contact with your skin, you will be burned badly.