Soda Can Calorimeter
Energy Content of Food
Introduction
Have you ever noticed the nutrition label located on the packaging of the food you buy? One of the first things listed on
the label are the calories per serving. How is the calorie content of food determined? This activity will introduce the
concept of calorimetry and investigate the caloric content of snack foods.
Concepts
•Calorimetry • Conservation of energy • First law of thermodynamics
Background
The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to
another. This fundamental law was used by scientists to derive new laws in the field of thermodynamics—the study of heat
energy, temperature, and heat transfer. The First Law of Thermodynamics states that the heat energy lost by one body is
gained by another body. Heat is the energy that is transferred between objects when there is a difference in temperature.
Objects contain heat as a result of the small, rapid motion (vibrations, rotational motion, electron spin, etc.) that all atoms
experience. The temperature of an object is an indirect measurement of its heat. Particles in a hot object exhibit more rapid
motion than particles in a colder object. When a hot and cold object are placed in contact with one another, the faster
moving particles in the hot object will begin to bump into the slower moving particles in the colder object making them
move faster (vice versa, the faster particles will then move slower). Eventually, the two objects will reach the same
equilibrium temperature—the initially cold object will now be warmer, and the initially hot object will now be cooler. This
principle is the basis for calorimetry, or the measurement of heat transfer.
In the 1770s, Joseph Black (1728–1799) was one of the first scientists to conduct calorimetry experiments with different
materials. He discovered that not all materials are equal when it comes to heat transfer. He concluded that different
materials have their own unique ability to retain heat energy. Some materials, like water, can gain a large amount of heat
energy without a significant change in temperature, while other materials, such as metals, will have a more dramatic
temperature change for the same amount of heat energy gained. This property is based mainly on the structure of the
material, the size of the atoms and molecules, and the interactions between them. This is known as the specific heat of the
substance. The specific heat is defined as the heat energy required to raise the temperature of one gram of a substance by
one degree Celsius. The unit of energy commonly associated with heat is called a calorie. Water has a defined specific heat
of 1 cal/g °C so it takes one calorie of energy to raise the temperature of one gram of water by one degree Celsius. (The
reverse is also true, remove one calorie of heat from one gram of water, and the temperature will decrease by one degree
Celsius.) With the specific heat of a substance known, the amount of heat energy gained or lost by a substance can then be
calculated if the temperature change is measured.
In this experiment, the specific heat of water and its change in temperature will be used to determine the caloric content
of a food sample. The normal unit for measuring the energy content in food is called a Calorie (with an uppercase C). A
Calorie is really a kilocalorie, or 1000 calories (lowercase c). During calorimetry, food burns and its stored energy is quickly
converted into heat energy and products of combustion (carbon dioxide and water). The heat energy that is released is then
transferred into the water above it in the calorimeter. The temperature change in the water is then measured and used to
calculate the amount of heat energy released from the burning food. The heat energy is calculated using Equation 1.
Q = mCT Equation 1
where
Q = heat energy
m = mass of the water
C = specific heat of the water
T = change in water temperature, T
final
– T
initial
(“” is the Greek letter Delta which means “change in”)
© 2016 Flinn Scientific, Inc. All Rights Reserved. 1
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