Science · 3rd Grade · Engineering Design and Innovation · Weeks 28-36

Brainstorming and Designing Solutions

Students will generate multiple possible solutions to an engineering problem and select the most promising one based on criteria.

• Common Core State Standards
• 3-5-ETS1-2

About This Topic

Brainstorming multiple solutions before selecting one is a critical habit of mind in engineering, and one that third graders often need explicit scaffolding to develop. The NGSS standard 3-5-ETS1-2 asks students to compare multiple possible solutions based on how well each meets the criteria and constraints of the problem. The natural tendency at this age is to latch onto the first workable idea , this topic teaches students to resist that impulse.

Generating multiple solutions requires students to understand the problem deeply enough to imagine different approaches to it. This means revisiting criteria and constraints before generating ideas, not after. Students also learn that constraints often rule out solutions that would otherwise seem promising , an important real-world engineering reality.

Active learning structures like gallery walks and structured argumentation are especially effective here because they make the comparison process visible and social. When students see multiple designs side-by-side and have to defend their selection with evidence, the quality of reasoning improves significantly compared to individual written responses.

Key Questions

1. Design multiple possible solutions to a given engineering problem.
2. Compare different design ideas based on established criteria and constraints.
3. Justify the selection of a particular design solution over others.

Learning Objectives

• Generate at least three distinct design ideas for a given engineering challenge.
• Compare proposed solutions against defined criteria, such as cost, materials, or effectiveness.
• Justify the selection of a specific design solution, citing evidence from the comparison process.
• Identify potential constraints that might limit the feasibility of a design idea.

Before You Start

Identifying Engineering Problems

Why: Students need to be able to clearly understand the problem before they can effectively brainstorm solutions.

Defining Criteria and Constraints

Why: Students must understand what makes a solution 'good' and what limits exist before they can generate and compare ideas.

Key Vocabulary

Brainstorming	A group creativity technique used to generate a large number of ideas for solving a problem.
Criteria	Standards or principles that are used to judge something; what makes a good solution for this problem.
Constraints	Limitations or restrictions that must be considered when designing a solution, such as time, money, or materials.
Prototype	An early model or sample of a product built to test a concept or process.
Feasible	Possible to do easily or conveniently; likely to succeed.

Watch Out for These Misconceptions

Common Misconception

The first good idea is the best idea.

What to Teach Instead

In engineering, early ideas are starting points, not final answers. Research on creative problem-solving shows that the strongest ideas often come after the obvious ones have been written down and set aside. Brainstorm sprint structures that require 5 ideas before evaluating any of them help students experience this directly.

Common Misconception

The best design is the most complicated one.

What to Teach Instead

Simplicity is often an engineering virtue. Fewer moving parts means fewer points of failure. Simpler designs are often cheaper and faster to build. When students compare designs using a criteria checklist, they frequently discover that a simple, well-matched design outperforms an elaborate one that only partially meets the criteria.

Common Misconception

Criteria and constraints are the same thing.

What to Teach Instead

Criteria describe what a successful solution must do (the bridge must hold 1 kg). Constraints describe the limits on how it can be built (only paper and tape allowed, must cost under $5). Criteria define success; constraints define the playing field. A solution that meets all criteria but violates a constraint isn't viable, regardless of performance.

Active Learning Ideas

Brainstorm Sprint: 5 Ideas in 5 Minutes

Give each student a sheet divided into 5 boxes. Present an engineering challenge (e.g., build a bridge that holds a textbook using only paper and tape). Set a timer for 5 minutes , students must sketch a different solution in each box without self-editing. Then pairs share and circle the 2-3 ideas they want to develop further. This separates idea generation from idea evaluation.

20 min·Individual

Gallery Walk: Design Comparison

Post 4-6 student design sketches (or teacher-prepared examples) around the room, each labeled with the design's key features. Students rotate with sticky notes: green for one strength, yellow for one concern. After the walk, each design's "wall" has peer feedback that the designer can use. Whole-class debrief: which designs addressed the criteria most completely?

35 min·Small Groups

Structured Argumentation: Defend Your Pick

Each group chooses one design from their brainstorm set and prepares a 2-minute argument: "We chose Design B because [evidence from criteria]. Design A would work, but it fails on [constraint] because..." Other groups ask clarifying questions. This pushes students to use criteria language rather than "I like it" reasoning.

30 min·Small Groups

Criteria Checklist Comparison

Provide a shared criteria checklist (co-created with students based on the problem). Teams score their top 2-3 designs against each criterion (1 = doesn't meet, 2 = partially meets, 3 = fully meets). Tally the scores and discuss: should all criteria count equally, or should some be weighted more heavily?

25 min·Small Groups

Real-World Connections

• Product designers at companies like IDEO use brainstorming sessions to generate many different concepts for new items, from furniture to electronics, before narrowing down to a few promising ideas to prototype.
• Civil engineers consider various bridge designs, weighing factors like span length, material strength, and cost (criteria and constraints) to select the safest and most efficient option for a specific location.
• Urban planners might brainstorm ideas for improving a local park, considering community needs, budget limits, and available space before proposing a final plan.

Assessment Ideas

Quick Check

Present students with a simple engineering problem, like 'design a way to keep a book dry in the rain.' Ask them to write down three different possible solutions on sticky notes. Collect the notes to see if they can generate multiple ideas.

Discussion Prompt

After students have brainstormed solutions to a problem, ask: 'Which of your ideas do you think would work best? Why? What makes it better than your other ideas? What problems might you run into trying to build it?'

Peer Assessment

Have students work in pairs to brainstorm solutions. Then, have them present their top two ideas to another pair. The second pair should ask questions like, 'What materials would you use?' and 'What could go wrong?' to help the presenters think critically.

Frequently Asked Questions

Why do students need to generate multiple solutions before choosing one?

Comparing multiple solutions is the mechanism by which engineers identify the best option , not intuition or preference. Generating alternatives requires deeper understanding of the problem and its constraints. Students who select the first workable idea often miss simpler or more effective approaches. The standard explicitly requires comparison, not just selection.

How do you teach students to compare designs fairly?

Co-create evaluation criteria with students before they design, so the criteria reflect the actual problem requirements. Use a shared scoring rubric or checklist that all designs are measured against. This prevents students from inventing new criteria that happen to favor their preferred design. Consistent criteria make comparison both fair and meaningful.

What counts as a "different" solution in this context?

Two solutions are meaningfully different if they use different approaches, materials, or mechanisms to meet the same criteria. Changing the color or size of the same design doesn't count. Helping students identify the core mechanism of each design (how it achieves the goal) helps them see whether they've genuinely generated distinct alternatives.

How does active learning improve the brainstorming and design selection process?

Social brainstorming structures , gallery walks, partner shares, structured argumentation , expose students to approaches they wouldn't have generated alone and require them to defend their reasoning. Individual brainstorming often stalls after 1-2 ideas; active, structured formats push students past that threshold and produce more diverse solution sets.