BioEd Online

Teacher Background

Living things that cannot harness solar energy through photosynthesis must eat other organisms, or the products of other organisms, as food. The amount of energy stored in food usually is measured in calories, with one calorie defined as the amount of energy required to raise the temperature of one gram (or one ml of water) of pure water one degree Celsius. The calories shown on most food labels are written with an uppercase “C,” which represents one kilocalorie or 1,000 calories.

The Children’s Museum of Houston’s PowerPlay exhibit is designed to help young people discover new ways to be physically active, and also to reinforce healthy behaviors. Students must be aware of the energy needed for the physical activities they do. They also must understand that different foods provide differing amounts of energy. Carbohydrates, fats and proteins are the main sources of energy in our food. Sugars, starches (such as those in bread, pasta and potatoes), and fiber (in many vegetables, whole fruits and whole grains) are the main forms of carbohydrates. Foods rich in fats include animal and vegetable oils, lard, butter and cream. Proteins, the building blocks of muscles and molecules within cells, are present in meats, eggs, and animal products, as well as in plant materials, like nuts and beans.

Each food group provides different amounts of energy. Fats and oils provide about nine Calories (Cal) per gram. Carbohydrates and proteins each provide four Cal per gram. Excess energy from food is stored in the body as fat.

Objectives and Standards

Texas Essential Knowledge and Skills (TEKS) Objectives

Science

2.9, 3.9, 4.9, 5.9

• Organisms and environments. The student knows that plants and animals have basic needs and depend on the living and nonliving things around them for survival.

Materials and Setup

Teacher Materials

• Single-hole punch

• Masking tape

• Nonflammable, flat surface (for students to use)

• Pair of scissors

Materials per Group of Students

• 6-in thermometer (°C)

• 2-cm piece of clay

• 2 different food labels

• 2 pieces of round, unsweetened oat cereal (Cheerios^®)

• 1/2 pecan (no shell)

• Graduated cylinder or beaker (100-mL)

• Large paper clip

• Matches or lighter

• Pencil (to be used as a holder for the can)

• Prepared soft drink can (bottom half of a soda can with two holes punched out at the top, aligned directly across from one another; cover sharp edge with masking tape; see illustration, PDF)

• Safety goggles for each student

• Water

• Copy of student sheet  

Procedure and Extensions

Engage

1. Ask students to discuss the basic needs of most living things. Make sure students understand that all living things need energy to live. Some organisms (mainly plants) use sunlight to make their own food, but many (including humans) rely on other living things for energy.

2. Have students pair off, and give each pair two different food labels. Instruct students to examine the nutritional information and read the calorie and nutritional information on each label. Ask, Do all types of food provide the same amount of energy?

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Explore

1. Challenge students to predict which provides more energy: a carbohydrate-rich food or an oil-rich food.

2. Have one student from each pair collect all materials for his/her team from a central area in the classroom.

3. Direct students follow the instructions on their activity sheets to complete the investigation. They will begin by pouring 50 mL of water into the prepared soft drink can and measuring the temperature of the water.

4. Next, students will create a food holder from the paper clip and clay (see illustration, PDF. They will hang two pieces of oat cereal on the paper clip and light them from below. They should hold the can by the pencil support, with the bottom of the can about one inch above the flame. If necessary, students should re-light the cereal pieces until they will no longer burn. When the flame has gone out, they should record the final water temperature.

5. Have students repeat the investigation using a piece of pecan that is approximately the same size as the two pieces of cereal together (place on top of the paperclip “holder”).

6. Have students follow the instructions on the student page to calculate the approximate number of calories released by the similar volumes of each food.

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Explain

1. Discuss results with the class. Ask, Which food released more heat when burned? Which food had more calories?

2. Help students understand that, due to the nature of the chemicals involved, fats and oils are more energy-rich than carbohydrates.

3. Fats are rich sources of energy. Certain fats and oils are healthier than others. Fats that are solid at room temperature, such as shortening, margarine and lard, should be avoided. In general, these fats are called “saturated” fats. Healthier choices are olive, flaxseed, nut, and fatty fish or canola oils (“unsaturated” fats). “Trans” fats are created by adding hydrogen to vegetable oil (hydrogenation). They are used in many commercially produced foods because they are less likely to spoil and have a longer shelf life. Trans fats are less healthy than many other forms of fat.

4. Foods that can contain large amounts of unhealthy fats include some red meats, whole milk dairy products and cream, some salad dressings, chocolate, cakes, cookies and some crackers.

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Elaborate

1. The first version of this activity had students compare similar “portion sizes” of cereal and pecan. Have students conduct the investigation again, using similar masses of cereal and pecan.

2. Have students weigh the pieces in advance and adjust the amount of each “fuel” tested to ensure that similar masses of cereal and pecan are compared.

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Evaluate

1. Give each student team two new food labels and ask them to determine the calories provided by each food group described on the labels.

2. Have students record the amounts of saturated fat, trans fat and sugar found in a serving of the food listed on the label.

Handouts and Downloads