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Daily Do

Why Does Some Food Disappear?

Welcome to NSTA's Daily Do

Teachers and families across the country are facing a new reality of providing opportunities for students to do science through distance and home learning. The Daily Do is one of the ways NSTA is supporting teachers and families with this endeavor. Each weekday, NSTA will share a sensemaking task teachers and families can use to engage their students in authentic, relevant science learning. We encourage families to make time for family science learning (science is a social process!) and are dedicated to helping students and their families find balance between learning science and the day-to-day responsibilities they have to stay healthy and safe.

Interested in learning about other ways NSTA is supporting teachers and families? Visit the NSTA homepage.

What is sensemaking?

Sensemaking is actively trying to figure out how the world works (science) or how to design solutions to problems (engineering). Students do science and engineering through the science and engineering practices. Engaging in these practices necessitates students be part of a learning community to be able to share ideas, evaluate competing ideas, give and receive critique, and reach consensus. Whether this community of learners is made up of classmates or family members, students and adults build and refine science and engineering knowledge together.


In today's Daily Do, Why does some food disappear?, students engage in science and engineering practices and use patterns as a thinking tool to make sense of the phenomenon of digesting a graham cracker. Students have an opportunity to apply physical science ideas about chemical reactions and physical changes to develop life science ideas about digestion (the beginning of the science idea the body is a system of multiple interacting systems). This task has been modified from its design to be used by students, families, and teachers in distance learning. While students could complete this task independently, we encourage students to work virtually with peers or in the home with family members.

Before you begin the task, you may want to access the accompanying Why does some food disappear? Google slide presentation.

What phenomenon am I exploring today? (Introduce Phenomenon)

If they are available at home, have students grab a box of graham crackers. Otherwise, show Slide 2 and/or share the graham cracker student handout, and ask, "What types of food molecules are in a graham cracker?"

Students may identify what categories are listed in the nutritional label or list ingredients. If students list ingredients, ask, "How could we categorize those?" (fats, proteins, carbohydrates, etc.)

To motivate students to investigate what happens when they eat graham crackers, say, "I wonder what happens to all these molecules when we eat graham crackers. Does anyone have any ideas?" Accept all student ideas.

Show Slide 3 and tell students you are going to share food molecule data (from a graham cracker) collected from three parts of the digestive system - mouth, beginning of the small intestine, and large intestine (you may choose to point out the parts on the diagram). Share that students will use the Identify and Interpret, or I2, data analysis strategy to help make sense of the data. Use Slide 4 to explain the strategy to students and then allow students to ask clarifying questions before moving onto data analysis.

Show Slide 5 and give students the Why does some food disappear? Student Handout. Help students orient themselves to the graph.

  • Ask, "Based on this graph, what food molecules make up an (uneaten) graham cracker?" This is denoted by the blue lines on the graph (water, protein, fats, glucose, other complex carbohydrates, and fiber).
  • Tell students that the x-axis represents the relative amount of each type of food molecule. The x-axis range is 0.0 to 1.0, but we've zoomed in to the part of the graph with data. To ensure students understand what is meant by relative amount, ask, "how much more other complex carbohydrates are in a graham cracker relative to water?" (three times more) "How much less protein is there relative to water?" (protein is about half the amount of water).
  • Support students in interpreting the other bars represented on the graph. Say, "Let's look at water. How does the amount of water molecules in an uneaten graham cracker compare to the amount of graham cracker water molecules in the mouth? (same amount) Beginning of small intestines? (same amount) Large intestines? (about half the number of original water molecules).


If students' productive struggle with the data is shifting toward frustration, go one step further:

  • "Take a look at AA, which stands for amino acids. How does the amount of AA molecules in the beginning of the small intestine compare to the amount in the uneaten graham cracker?" Students will notice there are no AA molecules in the uneaten graham cracker. You might say, "Where do you think the amino acids came from? Turn and talk with a partner." Students might say they think it used to be protein because the amount of protein molecules in the beginning of the small intestine is lower than the amount of protein molecules in the uneaten graham cracker. (Conservation of matter.) Tell students to record their ideas in the I2 table on their handouts.

Allow students time to complete questions 1-2.

Food Molecules in the digestive system

What does the data tell us? (Building Consensus)

Show Slide 6 and lead a building consensus discussion using the following prompts:

  • What did you identify, or see, in the data?
  • How did you interpret what you identified?
  • What ideas are we in agreement about?
  • Are there still places where we disagree? Can we clarify these?
  • Where should we go next to help us with areas where we are not sure/not in agreement?


Students will likely identify:

  • Amino acids (AA) are only found in the beginning of the small intestine and were not present in the uneaten graham cracker. This is the same for fatty acids.
  • Proteins, fatty acid, fats, glucose, and other complex carbohydrates are not found in the large intestine. (What happened to them?)
  • Some types of food molecules decrease from the mouth to large intestines and others decrease.
  • The amount of fiber molecules did not change during digestion.
  • The amount of water molecules decreased in the large intestines.


Students may interpret this as:

  • Our body digests (breaks down) proteins, fats, glucose, and other complex carbohydrates in the small intestine and "uses" them.
  • Our body takes in food molecules (nutrients) in the small intestines and that's why they aren't found in the large intestine.

Motivate digging deeper into what happens to carbohydrates during digestion by saying, "I am wondering why some of the carbohydrates disappeared but fiber didn't. What's up with that?" Question 3 on their student handout is place for students to capture their initial ideas.

Use the prompts on Slide 7 to allow students to share their initial ideas and come up with ways we could investigate our ideas. Students will likely indicate they want to look closer at the structure (or size) of the different carbohydrates.

Table 1
Glucose Molecule Starch (Complex Carbohydrate) Molecule Fiber Molecule

Glucose Molecule

Starch (Complex Carbohydrate) Molecule

Fiber Molecule

Why are some molecules disappearing and other's aren't? (Digging Deeper)

Show Slide 8 and explain to students that you found these molecular models of glucose, starch, a complex carbohydrate, and fiber. Ask students what they have heard about these molecules to identify prior knowledge. Students may know that some foods, like bread or potatoes, contain a lot of starch or that fiber helps make you poop. Others may know that glucose is something that diabetics monitor.

Allow students time to examine Slide 8 in order to answer question 4 on their student handouts. Lead a discussion and allow students to share out what they noticed, similarities, and differences.

Students should identify the following:

  • All three contain the same atoms - carbon, hydrogen, and oxygen
  • Glucose is the smallest and fiber is the biggest
  • Both starch and fiber contain the same structure of atoms as glucose; it looks like starch and fiber are made of many glucose molecules connected together

What did we figure out? (Making Sense)

Show Slide 9 and lead a discussion using the prompt:

How could the structure of the different carbohydrate explain why some carbohydrates are digested (broken down) and others are not?

Students may say the large size of a fiber molecule might explain why our body's digestive system can't break fiber down (digest the fiber). Other students may pose the opposite - that glucose and starch are smaller molecules so our digestive system has an easier time breaking them down (digesting them).

Have students summarize the discussion in question 5 of their student handouts. This question can be used as a formative assessment to check for student understanding.

NSTA Collection of Resources for Today's Daily Do

NSTA has created a Why does some food disappear? collection of resources to support teachers and families using this task. If you're an NSTA member, you can add this collection to your library by clicking ADD TO MY LIBRARY located near the top of the page (at right in the blue box).

Check Out Previous Daily Dos from NSTA

The NSTA Daily Do is an open educational resource (OER) and can be used by educators and families providing students distance and home science learning. Access the entire collection of NSTA Daily Dos.


This Daily Do is inspired and uses materials from the How do things inside our bodies work together to make us feel the way we do? storyline created by OpenSciEd. OpenSciEd is an open educational resource that can be used by parents and teachers to implement student-driven learning.


Is Lesson Plan Life Science


Middle School

Asset 2