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Examining Nutrition

Investigation 1 – Lab

Back to Investigation 1

BE PREPARED

Supplies and Equipment:

Class Materials:

1 flip chart
1 human torso
1 timer
500 ml of vinegar
Paper chart or blank transparency sheet

Group Materials:

1 400 ml beaker
1 stick of white anti-dust chalk, Crayola
1 thermometer

Individual Materials:

1 Student Data Record

Teacher Preparation:

1. Set up the resource materials (the encyclopedia, flip chart, and human torso) students will use for reference at a central point in the classroom. The human torso will need to be placed where it can be explored by one group at a time.

2. For each group, pour 100 ml of vinegar into a 400 ml beaker.

3. Place the materials each group will need at a distribution point.

4. Separate the class into five cooperative groups.

Instruction:

1. Instruct each student group to obtain the following necessary materials from the distribution point: One (1) 400 ml beaker filled with vinegar and one (1) piece of chalk.

GET FOCUSED

Investigation One introduces students to mechanical and chemical digestion.

INVESTIGATE

Trial 1

1. In Trial 1, students will explore the digestion of food. They will accomplish this by simulating two forms of digestion: mechanical (physical) and chemical.

Mechanical digestion is modeled by breaking a stick of chalk, which changes the chalk physically but not chemically. Chemical digestion is modeled by placing the pieces of chalk into a beaker of vinegar. The vinegar and chalk undergo a chemical reaction that is shown by the release of gas in the form of bubbles of carbon dioxide. The release of gas, however, is not instantaneous. Therefore, in order to observe the signs of the chemical change, it will be necessary to allow the reaction to continue for a short period of time before students observe the results. During this time period, students should complete the next step of the Lab, then return to this experiment. The passages that follow are provided to assist with the direction of the students as they conduct their experiment. The question students will investigate in this part of the Investigation is:

What is the difference between mechanical (physical) and chemical digestion?

Note: For this part of the Investigation, students will focus on only three signs of chemical change (unexpected color change, change in temperature, and release of gas). This is because these three signs can be easily identified and understood by the students as they conduct this experiment.

a. Direct a student in each group to break the piece of chalk into several pieces. Ask them:

• Did you change the physical form of the chalk? Yes. The chalk was broken into smaller pieces. Both the size and shape of the chalk changed when it was broken.

• Did the chalk become a different substance? Did you notice any of the signs of a chemical change that would make you think the chalk was a different substance? No. When the chalk was broken, none of the signs of a chemical change were observed. Students should observe that the chalk felt the same temperature as before it was broken, that there were no unexpected color changes, and that no gas was released as the chalk was broken. This should lead students to conclude that the chalk was still chalk.

Do you think the chalk changed physically or chemically? Why? Tell students to record their answer in Problem 3d of their Student Data Record.

b. Remind students that mechanical digestion refers to the physical changes in food. Ask students: Which type of digestion did breaking the chalk represent? Tell students to circle their answer in Problem 3e.

c. Instruct students to place the pieces of chalk into the beaker of vinegar and to record the temperature of the contents of the beaker in Problem 3f of their Student Data Record.

d. Encourage students to observe what occurs for one minute, including an observation of the temperature of the beaker contents. Ask students: Did the chalk change after it was added to the vinegar? Tell students to describe what they observed in problem 3h.

e. Direct students to set aside the beaker of chalk and vinegar. Explain that they will return to this experiment at a later point during the Lab.

Note: At this point, conduct Trials 2 and 3 of the Lab. After completing these Trials, return to continue the remainder of Trial 1.

f. Direct students to return to the beaker of chalk and vinegar. Encourage them to observe any changes, including any changes in temperature, that may be occurring between the chalk and vinegar and to ask themselves the same questions that were asked when the chalk was broken into smaller pieces.

g. Tell students to work in their group to answer Problems 3i – 3n in their Student Data Record.

Note: While the chalk is reacting, continue with the remaining portion of Trial 2 of the Lab.

Trials 2 and 3

2. In these Trials, students will explore the parts of their body that function together as the digestive system. They will use several resource materials to accomplish this task, such as the human torso and flip charts. Any available posters or materials that apply to this task may also be used. In Problem 4 of their Student Data Record, students will use the resource materials to identify the components of the digestive system. In Problem 5, the students must physically handle the human torso in order to answer several application questions. During this part of their exploration, student groups should take turns working with the torso. The passages that follow are provided to assist with the direction of the students as they conduct their experiment. The question students will investigate in this part of the Investigation is:

What are the parts of the digestive system and their functions?

a. Ask students to locate problem 4 in their Scientist Data Record. Tell them that they may use the Human Body Encyclopedia, human torso, and flip charts to complete this activity.

b. Explain that each statement listed in Problem 4 describes the function of one part of the digestive system. Ask students to identify the part of the digestive system described in each statement. Tell them to record their answers in the space provided.

c. Encourage students to identify each part described by drawing an arrow from the description to the corresponding part of the digestive system in the illustration.

d. After students have accomplished this task, direct them to answer and record the questions listed in Problem 5 of their Student Data Record, which relate to the human torso. Tell students they will need to explore the human torso to answer the questions. Explain that each group should take turns visiting the torso.

Note: At this point, students should return to Trial 1 to complete their observations of the chalk in the vinegar.

3. Ask students to get ready to use a Cognitive Tool called Mind Movie to help them learn what happens during the digestion process.

4. Optional Extension: Instruct students to work in their groups to identify the nutrients necessary for their bodies to function properly. Tell them to use the resource materials (flip charts and human torso) to accomplish this task. Inform students that they may record this information on the back of their Student Data Records.

5. Upon completion of the experiment, permit enough time to clean up the lab and return the materials and equipment to their assigned location.