Top image: Assortment of seeds (photo by Let's Talk Science)

Setting the Stage

Prior Skills and Knowledge

To successfully participate in this Design & Build, students should be able to use basic cutting tools and fasteners and have a basic understanding of how to sort by size.


Corn being harvested using a corn picker
Source: Wikimedia Images via Pixabay

Seeds are an important part of the natural world and the business of agriculture in Canada. Many kinds of seeds become food for animals and humans. Some seeds are used to produce more crops and grow more food in following years. Canadian farmers also sell their crops as seed to other farmers all around the world to produce food and animal feed.

Before crops are sold, they are graded (like getting a mark at school) based on the quality of the seeds and the amount of weed seeds in the crop. If a crop has fewer weed seeds in it and the crop has larger, more uniform seeds it gets a better grade because bigger seeds usually produce stronger new plants. To have the best seeds for different purposes (seed stock, human food, processed foods and animal feed, etc.) seeds must be sorted.

In this Design & Build challenge, students will work collaboratively towards a common goal of constructing a sorting device that will assist students to sort seeds by size.

Cob of dry field corn
Source: Pexels via Pixabay

This design and build could begin from:

  • exploring photos of crops being harvested. Discuss using questions such as:
    • “Why does a grain company need to sort seeds? How do they do this?”
    • “In a huge field there might be some weeds that grow as well as the crop. How do you think grain companies remove weed seeds from the crop seeds?”
  • exploring real ears of corn, heads of wheat or barley or soybean pods. Discuss using questions such as:
    • “Do all the seeds on this corn cob/wheat head/soybean pod look the same? Are all seeds of a crop the exact same size?”
    • “Would you want to eat all of these kernels/seeds?”
  • Reading a book such as The Empty Pot by Demi. Discuss using questions such as:
    • “How does the emperor choose which person will replace him as emperor?”
    • “What do you think are the qualities of a good emperor?”
  • Cover of The Empty Pot by Demi
    Source: Open Library

    • “What was the problem with the seeds he gave to the children to plant? What was the emperor really trying to prove?”
    • “Was the emperor successful at finding the best kind of new emperor?”
    • “We sometimes hear the expression – ‘he/she is a good seed’ or ‘he/she is a bad seed’. What do you think that means?”

Design Criteria

As a class, students brainstorm criteria that their prototype seed sorter must meet. Educators may choose to add other criteria that are curriculum-specific, such as using joiners/fasteners, measuring, using specific materials, etc.

Design criteria examples:

  • The seed sorter will sort seeds into three different sizes
  • The seed sorter must use at least one type of fastener
  • The seed sorter cannot require outside force (e.g., shaking it) to work

Materials and Preparation (Click to Expand)


Suggested materials
Source: Let's Talk Science

  • Seeds of three distinct sizes for sorting (e.g., large: lima beans/kidney beans; medium: soybeans/popcorn; small: tomato seeds/millet/rice/barley) – alternately, use commercial bird seed
  • Funnels of different sizes
  • Paper or Styrofoam cups, varied sizes
  • plastic flat-bottomed containers or trays to catch and contain seeds
  • construction paper and/or cardstock
  • paper punches or craft punches of different sizes
  • other materials such as craft sticks, drinking straws, string
  • tools and fasteners such as tape, glue, other fasteners
  • scissors


  • Collect an assortment of recycled and new materials that students will use to construct the prototype seed sorter. The materials list above is only a suggested list.
  • Set up material sourcing stations, organized by type of material. Alternatively, organize an assortment of materials to be provided.
  • Source and combine seeds for sorting.
  • If there are students with allergies or concerns about using food seeds for this challenge, consider substituting beads of 3 different sizes. Check that the smallest beads will be able to go through one of the available funnels.

What To Do

Students develop Design & Build skills as they design, build and test a seed sorter that will separate seeds into at least three different sizes.

Students will follow the steps of the Design & Build process:

  • identify the problem to be solved/need to be met
  • brainstorm criteria that the prototype must meet
  • share their questions and ideas for a solution to the problem/need
  • discuss the pros and cons of each in order to select a potential solution to be tested
  • visualize what the solution might look like and make design sketches based on their visualizations
  • identify the tasks or key steps involved in developing the solution (the design plan)
  • make decisions about tools and materials that will be needed
  • build/develop the design idea based on their sketches and design plan
  • test their prototypes based on the design criteria
  • modify the prototype and retest it against the design criteria as necessary
  • reflect on their results and identify things that could be done to improve their prototypes


Observe and document, using anecdotal comments, photos and/or video recordings, student’s ability to:

  • Work Collaboratively – students work collaboratively to complete a task and evaluate their group processes throughout the Design & Build process
  • Generate Ideas – students use idea generation strategies, such as brainstorming, to identify possible solutions as well as make decisions about the pros and cons of each solution
  • Communicate – students communicate their thinking and learning in words and/or sketches and/or photos and/or videos, etc. (e.g., in design plans that include 2D design sketches, in outlines of key design steps/tasks, in lists of required materials/equipment/tools)
  • Work Safely – students demonstrate safe practices when using a variety of tools and materials while building/creating prototypes
  • Reflect – students reflect on the results of their prototype testing and suggest things that they might do differently to improve their prototypes

Co-constructing Learning

Saying, Doing, Representing

Educator Interactions:
Responding, Challenging

Students identify and refine the problem to be solved/need to be met.

  • “What does sorting mean?”
  • “How could you sort something without using your hands?”

Students brainstorm and record criteria for the seed sorter.

  • “What should the seed sorter be able to do? What design criteria must your prototype meet?”
  • “What forces acting on your seeds could help in the sorting process (e.g., gravity)?”
  • “What words could we use to describe some of the attributes/qualities the seed sorter must have to be effective?" (e.g., accurate, easy to use, fast, etc.)
  • “Have you ever used or seen any other tools or machines that help separate things? What did they look like?”

Students visualize what the solution might look like and make design sketches based on their visualizations.

  • “Why do engineers label all the parts of their design drawings?”
  • “How will you represent each part of your seed sorter prototype in the design sketch?”
  • “How does your seed sorter design plan meet the design criteria?”

Students make observations and decisions about the available tools and materials.

  • “How could the materials we have here be used to sort seeds of different sizes?”
  • “What tools will you need to build the seed sorter you have designed?”

Students build/develop and test the design idea based on their sketches and design plan (create the “prototype”).

  • “How will you test your seed sorter?”
  • “Which of the design criteria does your prototype meet? Which ones does it not yet meet? Why do you think this happened?”
  • “Does your seed sorter prototype sort the seeds the way you planned? Why or why not?”

Students modify the prototype and retest it against the design criteria as necessary.

  • “What problems did you have when you re-tested your seed sorter?”
  • “What changes in your model might improve your results?”
  • “How would it change your design if you had to sort five sizes of seeds?”

Students reflect on the results of their testing and identify things that could be done differently in the future.

  • “What materials worked best? What materials did not work as well?”
  • “How is your seed sorter like those of your classmates? How is it different? Why do you think that is?”
  • “What have you learned about how solid materials can be sorted by doing this challenge?”
  • “How did your team work together to solve the problem? What challenges did your team have in working together?”

Cross-Curricular Connections


  • Ask questions (e.g. “Why do we need to sort seeds? How can technology help us do these tasks?”)
  • Communicate thoughts, feelings and ideas (e.g. brainstorm unique ways to use materials to sort the seeds; propose improvements to the initial seed sorter design; present results of the Design & Build process; discuss other seed-related technologies that are involved in farming and agriculture)
  • Use a variety of forms (e.g., oral, written, graphic, multimedia) to communicate with different audiences and for a variety of purposes (e.g., make a prototype model of a seed sorter)

Mathematical Thinking

  • Measure the diameter of the seeds (mm) in preparation for designing and building the seed sorter
  • Using spatial reasoning and sequencing when designing and constructing the seed sorter

Visual Arts

  • Sketching, representing and modeling the seed sorter prototype

Computational Thinking: Abstraction

  • Use spatial reasoning and sequencing when designing and constructing the seed sorter (e.g., draw a concept design of a seed sorter)

Extending the Learning

Soybeans germinating
Source: jcesar2015 via Pixabay

If your students are interested in learning more, the following may provoke their curiosity:

  • Conduct another inquiry to compare the germination process in different plant species from the seeds that have been sorted in this Design & Build. Is there any connection between the rate of germination and the size of seeds (e.g., do small seeds germinate faster than large seeds?)?
  • Indigenous cultures have legends and traditional agricultural customs that involve growing crops together, as opposed to single-species crops (monoculture). The Three Sisters Legend is based on the practice of growing corn, beans and squash together. The corn supports the growing beans and the leaves of the squash cover the ground around the base of the plants to stop weeds from growing. Have students watch a video of The Three Sisters Legend, without telling them which plants each of the girls represents.
  • Participate in Tomatosphere™ by Let’s Talk Science and learn about the effects of the space environment of the germination of tomato seeds.