This is the first Investigation in the LabLearner CELL Examining Nutrition.

A. Begin the Investigation by describing the focus of the CELL to the students.

1. This CELL is designed to introduce basic concepts of how food is processed or digested in order to provide nutrients necessary to the human body. It will also increase students’ knowledge of how to provide their bodies with a balance of nutritious foods in order to maintain good health.

2. During the Investigations, students will explore the components of the digestive system, mechanical and chemical digestion, the use of the MyPlate, nutrition labels, and the Daily Values (DV) of nutrients needed for a healthy body. They will examine the role of nutrients in the health of their body and how eating excess or limited nutrients can affect their health.

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Encourage students to Recall what they know about the digestive system. If students have difficulty beginning, use the following questions to help prompt the recall process: 

1. Ask students: Why do we eat food? Student answers may vary.  Students may suggest that our bodies get hungry.

2. Ask students: Why is food important? Student answers will vary. Students may suggest food is necessary to stay alive and that food provides energy.

3. Ask students: How do our bodies obtain the food they need to live? Student answers may vary. Students may suggest that their digestive system aids in supplying the food they need.

4. Ask students: Why is the digestive system important? Student answers will vary. The digestive system breaks down food so that it can be delivered to the parts of the body that need nutrients from the food.

5. Ask students: What do you know about the parts of our bodies that are used to digest food? Students may suggest that the mouth, throat, and stomach are used. Guide them to recall that the teeth, tongue, esophagus, small intestines, and large intestines are also used to digest food.

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B. Narrow the focus of the discussion by explaining that in Investigation One of the CELL students will learn basic information about the digestive system and the process of digestion.

1. Begin by directing students to use a Cognitive Tool (previous slide) to help them recall any useful information they may already know about the topic.

2. Encourage students to locate their Scientist’s Glossary. Initiate a discussion about the process of digestion by asking them:

a. Ask students: What is considered food? Student answers may vary. Guide students toward understanding that food is any substance that can be eaten or drunk and is used by the body in order to live.

b. Ask students: How do we know that our body needs food? Students should indicate that they feel hungry or that their stomachs growl or rumble. In addition, students may feel light-headed or dizzy if they need to eat.

c. Ask students: How is food changed so that our bodies can use it? Students should indicate that the organs and parts of the digestive system use the process of digestion to make food usable by our bodies. Food is digested or broken into smaller pieces or substances that the body can use.

d. Ask students: What are these smaller pieces or substances called?  What are they? Student answers may vary. Substances that the body uses for energy in order to function are called nutrients.

e. Tell students that the six essential nutrients the body requires are: water, proteins, carbohydrates, fats, vitamins, and minerals. Explain that nutrients are the substances in food that the body uses to function, but that the body must first digest or break foods down the food in order to access the nutrients.

f. Ask students: How does the digestive system break down food into nutrients? Student answers will vary.

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C. Explain to students that in order for them to understand how their digestive system provides the nutrients their bodies need to function, they will need to know the components of the digestive system and the function each component performs. Use this slide as a visual aid during the discussion.

1. Direct students to locate Problem 1 of their Student Data Record. Explain that they should record each part of the digestive system as it is discussed in class.

2. Ask students to look at the definition for digestion in their Student’s Glossary. Explain that there are several organs and structures within the digestive system that help to break down food and that food travels through these organs and structures in a one-direction path.

3. Direct students to look at the diagram on the slide. Ask student: Where do you think the digestive process begins? Students should indicate that they place food into their mouth, then chew the food with their teeth.

4. Ask students: What do you think happens next? Where does the food go? Student answers may vary.

5. Tell students that after they swallow, food moves through the throat and into the esophagus. The esophagus is a long tube of muscles that connects the throat to the stomach. It pushes food into the stomach by rhythmically contracting its muscles.

6. Continue prompting students by asking students: What do you think happens next? Where does the food go? Allow students to suggest the next organ or structure of the digestive system and then continue with the prompt. 

Repeat this process until all of the organs/structures of the digestive system on the slide have been discussed. When completed, the discussion should cover the following organs and points.

a. From the stomach, the food moves next into the small intestines, where it is digested further. The nutrients in the food move, are absorbed through the walls of the small intestine, and are transported to the tissues of the body.

b. In the large intestine, water and some vitamins are absorbed. In addition, any undigested food particles are compacted in the large intestine and are passed out of the body.

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D. Continue the discussion of digestion by reminding students that there are two types of digestion: mechanical and chemical.

Note: Students should not use their Scientist’s Glossary at this point. They will perform an activity, which is described in Problem 2a, that will involve students’ preconceptions of these terms.

1. Ask students: What do you think each of these terms means? Student answers may vary.

2. As a way of assessing and encouraging students’ prior knowledge of these terms, conduct the following activity:

a. Divide students into five cooperative groups. Encourage each group to locate Problem 2 on their Student Data Record. In Problem 2a they should observe the words mechanical and chemical.

• • Provide students five to ten minutes to discuss these two words and decide on three words that they would associate with the term mechanical and three words that they would associate with the term chemical.
  • Tell students that they may record any word that they associate with these terms. However, students should not be permitted to use wording from the definitions of these terms from their Scientist’s Glossary.
  • Students should record the words under the appropriate heading in Problem 2a of their Student Data Record.

b. After the time period has elapsed, ask each group to share their words with the class. Record each group’s words on a piece of paper so that the words can again be referenced at the end of the Investigation.

c. After all groups have shared their ideas, pose a second question for the groups to discuss: 

Ask students: What do you think food looks like after it has been mechanically digested? After it has been chemically digested?

Direct students to Problem 2b in their Student Data Record. Explain that in Problem 2b students should predict either through a written description or diagrams, what the piece of food at the top of the question might look like after both types of digestion.

• Provide time for student groups to discuss and record their ideas in Problem 2b and then encourage the groups to share their ideas with the class.
• Record students’ ideas on the paper so that students can refer to the information at the end of the Investigation.

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3. Reaffirm that all of the students’ ideas about mechanical and chemical digestion were a good start to understanding what scientists mean by each. Explain that one of the experiments they will conduct in the lab will help them to better understand the differences between each. However, there is some information that may be helpful to them before they conduct their experiments.

4. Tell students that if a scientist had performed the word association activity they might have written down the terms shown on this slide.

5. Explain to students that when a physical change occurs, only the state of matter or physical form of the substance changes. When a chemical change occurs, the original substance becomes a different substance. The original substance cannot be recovered.

We will look at Physical Change on the next slide. ➡

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6. Ask students: What do you think scientists mean by physical form? Student answers may vary. Students should suggest physical form indicates properties such as size or shape.

In this slide, the State of Matter is represented on the left by the melting popsicles. A phase change from solid to liquid occurs as the popsicles melt. 

Physical Form is represented on the right of this slide by the glass. Even though the broken glass looks quite different from the unbroken glass, it is still composed of the exact same material. If you kept breaking the glass into small pieces, it would look less and less like a drinking glass. However, it would still be the same shattered glass, it will not have changed into something other than glass.

On the next slide, we will see that the situation is quite different for Chemical Digestion and Chemical Change.➡

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7. Ask students: How could you tell if a chemical change had occurred to your food and that it had become a different substance? Student answers may vary.

8. Explain that scientists have identified ten common signs that can be used to identify a chemical change. List the changes on the board.

a. A change in volume.

b. A change in temperature.

c. An unexpected change in color.

d. A change in electrical conductivity.

e. A precipitate forms (a chemical falls out of solution as a solid or a liquid.

f. A gas is produced.

g. A change in pH.

h. A change in chemical or physical properties occurs.

i. A change in odor.

j. A change in melting or boiling point.

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9. Ask students: Based on what we just discussed, what might you look for when trying to determine whether food was digested mechanically or chemically? Student answers will vary. Students should indicate that it would be important to pay attention to changes in the shape, size, and color of the food before and after digestion as well as whether the change in the food was accompanied by one or more of the signs of a chemical change. The signs of a chemical change would help to indicate whether the product of digestion was a new substance.

E. Tell students they will conduct experiments in this Investigation that will help them continue their exploration of the similarities and differences between the two types of digestion. As they conduct their experiments, they should think about the following questions:

How does your food change as it moves through the digestive system?

How is the mechanical digestion of your food different from chemical digestion?