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A1.3 · Design, build, and test a device, model, structure, or system

Learn to design, build, and test a device, model, structure, or system through clear examples and targeted practice.

Ontario Grade 9 Science

STEM Skills, Careers, and Connections

A practical guide to improving a science solution

A paper airplane that glides only a short distance gives us something useful to investigate. We can ask how to make it travel farther, then design, build, and test a version. The aim is not to guess the perfect answer at once. It is to make a plan, use evidence, and improve the design. In this lesson, a design is a planned way to meet a need. A model is a simplified version of something real. A test is a planned way to find out how well a design works.

What you will learn

Describe how a design need can be turned into a clear question and criteria.
Plan and build a simple model, device, structure, or system safely.
Test a design fairly, record evidence, and use results to make an improvement.
Explain what a test can and cannot show.

1. Begin with a need and a question

A design task starts with a need or problem. For example, a class wants a paper airplane that can travel farther across a clear indoor space. A useful question focuses on a change that can be tested: “Can changing the wing shape help this paper airplane travel farther?” This is clearer than “How do we make the best airplane?” because “best” is not defined.

Next, set criteria and constraints. Criteria are features a successful design should have. A criterion here could be that the plane travels farther than the original design. Constraints are limits the design must follow, such as using one sheet of classroom paper or staying inside a marked test area. Clear limits help keep the task manageable and safe.

Before building, consider what you already know and what you need to find out. A paper airplane can be folded in different ways, but a change may help, do little, or make the plane less stable. Treat those ideas as predictions, not facts. A prediction can guide a test, but evidence from the test is needed to judge the design.

Describe the need in plain language.
Write a question that focuses on a testable design choice.
State success criteria and practical constraints before building.

2. Plan and build a model

A sketch or labelled plan can show the main parts of an idea before you build it. Labels tell a reader what each part is meant to do. For an airplane, a plan might identify the wings and body and mark which wing shape will change. The drawing is a model: it helps us think and communicate, but it is not the real airplane and cannot show every detail of flight.

A useful design plan links each part to the need. Choose materials that are available and appropriate. Build carefully, following the plan, and check that the finished item matches it. If you must change the plan while building, note what changed and why. This makes the process easier to understand and repeat.

The same approach applies to many science contexts. A model can represent a cell, a simple circuit, or the positions of objects in space. A structure might be a paper bridge. A system is a set of parts that work together, such as a classroom method for sorting materials. These examples are ways to practise the same design skill; they do not replace the need to check whether a particular model represents its real subject well.

Use a labelled plan to communicate the design.
Build within the stated constraints and record important changes.
A model is useful for a purpose, but it leaves out details of the real thing.

3. Test fairly and use evidence

Evidence is information gathered during a test that helps answer the question. For the airplane, distance travelled could be recorded for each flight. To make a fair comparison, use the same launch location and the same type of paper for both designs. Keep the test area clear, and have one person launch each plane in the same way if possible. Change the wing shape being investigated, rather than changing several design features at once.

Repeat the test when practical. A single flight may be affected by an uneven launch or a small air current. Repeated results can show whether the design seems to work consistently. Record what happened, including results that do not fit the prediction. Do not change or invent measurements to make a design look successful.

Evidence supports a limited conclusion. If the changed design travels farther in repeated tests under the same conditions, that is evidence that the change helped in this test. It does not prove the design will always travel farther in every room or for every person. A test gives information about the conditions used. A model also has limits: a paper airplane is not a full-scale aircraft.

A scientific result and a social or ethical judgment are different. Test results can help show how a design performs. A choice about whether a design is fair, affordable, or appropriate may also involve people’s needs and values. Keep those kinds of claims distinct.

Use the same conditions for a meaningful comparison.
Record observations honestly and repeat tests when practical.
Match the conclusion to the evidence and name important limits.

4. Improve the design

Testing is not only a final check. It can help guide a next version. Compare the results with the criteria. If the design did not meet them, ask what part might be changed. If it did meet them, consider whether a further test is needed before making a broad claim.

Make one focused improvement, then test again under comparable conditions. This makes it easier to tell which change may have affected the outcome. Keep a brief record of the question, plan, build changes, test conditions, results, and next step. This record lets someone else understand what you did.

The flow diagram below summarizes this process. Its arrows show a useful order, but real design work may return to an earlier step. For example, a test may reveal that the original question or criteria need clarification. There is no guarantee that every first design will succeed; learning from an unsuccessful test is part of the work.

Use test results to choose a focused improvement.
Test the improved version under comparable conditions.
Return to earlier planning steps when the evidence shows a need.

A simple design cycle

Stage	What to do	Example evidence or record
Define	State the need, question, criteria, and limits	A clear question and success criterion
Plan	Sketch, label, and choose materials	A labelled plan
Build	Make the planned version safely	Notes about changes
Test	Use comparable conditions and record results	Observations or measurements
Improve	Use results to choose a next change	A reasoned next step

Worked example

Example 1: Compare two paper airplanes

A student wants to find out whether a wider wing helps a paper airplane travel farther. Describe a suitable design-and-test plan.

Plan a fair comparison

A planning flow for comparing paper airplanes. It does not show measured results or guarantee an outcome.

Set the question and criteria
Ask whether the wider-wing version travels farther than the original. Use travel distance as the success criterion. Keep both designs within the same paper and indoor-space limits.
Plan a fair comparison
Build two planes that differ in wing width but use the same kind of paper. Choose the same launch line and a clear, level indoor area. Use the same launcher and launch method for each design.
Record and interpret
Measure and record each flight using the same method, and repeat the comparison when practical. If the wider-wing plane travels farther in repeated trials, conclude that it did better under these test conditions. Do not claim that wider wings will always travel farther.

Answer: The plan changes wing width while keeping other important conditions as similar as possible. It compares recorded results and limits the conclusion to the test.

Check: The plan is useful because it addresses the question with observable evidence. Launch differences and indoor air movement may still affect results.

Worked example

Example 2: Improve a paper bridge

A group builds a paper bridge to span a small gap between two books. The bridge bends when a few identical counters are added. How can the group use the design process to improve it safely?

Improve a bridge design

This flow shows a possible design cycle. The bridge shape and test outcome are not drawn to scale and no result is implied.

Clarify the goal
Set a criterion such as supporting more counters without the bridge touching the table. Keep constraints clear: use the allowed paper and the same gap between the books.
Choose and build one change
The group could fold the paper into a different shape. Sketch and label the new plan, then build it. Keep the support points and gap unchanged so the versions can be compared.
Test and decide what follows
Add counters one at a time, using the same type of counter and placement method for each version. Stop if the bridge becomes unstable. Record the result, then compare it with the original. A better result supports an improvement for this setup, not a claim about every paper bridge.

Answer: Change one feature, such as the fold, while holding the gap and support setup steady. Test cautiously with the same counters and record the comparison.

Check: Stopping when the bridge is unstable reduces the risk of a sudden collapse. The result is limited to the materials and setup used.

Worked example

Example 3: Test a simple sorting system

A class wants a model system that sorts classroom cards into two labelled groups. How should students decide whether their system works?

Test a sorting system

This is a simplified process model, not a claim about real sorting data or every sorting system.

Define success
Write a rule for which card belongs in each group. A suitable criterion is that the system puts each card into the group named by its feature, using the same rule each time.
Build a clear model
Make two labelled spaces and a written sorting rule. Use practice cards with clear features. The labelled spaces and rule form a model of a sorting system; they represent the process but do not show every real-world sorting task.
Test with examples
Sort a planned set of cards, then check each placement against the written rule. Record any card that is difficult to classify. If the rule is unclear, revise it and test a fresh set. Do not hide confusing cases; they show where the system may need improvement.

Answer: Students should state a sorting rule, test the placements against it, and record unclear cases. They can improve the rule and test again.

Check: The evidence is the observed match between card features and the rule. Success with practice cards does not prove that the system handles every kind of sorting task.

Common mistakes and how to avoid them

Changing several features at once and then saying which one caused the result.

Correction: Change one main feature at a time when possible, so the comparison is easier to interpret.

Calling one successful test proof that a design always works.

Correction: Describe what happened under the conditions tested and state what remains uncertain.

Ignoring results that do not match a prediction.

Correction: Record all results. Unexpected evidence can point to a design change or a better question.

Treating a model as an exact copy of reality.

Correction: Explain what the model represents and what details it leaves out.

Lesson summary

Start with a clear need and a question about a design choice.
Set criteria for success and limits that the design must follow.
Plan and label the design before building; record changes.
Test fairly, record evidence honestly, and repeat when practical.
Use evidence to improve the design and keep conclusions within the test’s limits.

Check your understanding

Question 1

A student changes a paper airplane’s wing width and paper type at the same time. What is the main problem?

The student cannot tell which change may have affected the result.
The airplane has become a scientific fact.
The test has no need for a question.
The student has proved that both changes always help.

Show answer and explanation

The student cannot tell which change may have affected the result.

Changing two features together makes it harder to connect a result to one particular change.

Question 2

A model bridge holds more counters in one classroom test than its earlier version. Which conclusion is best?

The new bridge will hold more weight in every situation.
The new version performed better in that test setup.
The test proves that all folded paper is stronger.
The result is a social judgment, not evidence.

Show answer and explanation

The new version performed better in that test setup.

The evidence supports a conclusion about the conditions used, not every possible bridge or test.

Question 3

Why should a designer record an unsuccessful test?

It can show what needs to be changed or tested next.
It makes the design successful automatically.
It replaces the need for criteria.
It proves the model exactly matches reality.

Show answer and explanation

It can show what needs to be changed or tested next.

An unsuccessful result can still provide useful evidence for improving the next version.

Key terms

Design: A planned way to meet a need or solve a problem.
Model: A simplified representation of something real or an idea.
Criteria: Features used to judge whether a design meets its goal.
Constraint: A limit that a design must follow.
Evidence: Information from observations or measurements that helps answer a question.
Fair comparison: A comparison in which important conditions are kept similar so the design versions can be judged.

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About this lesson and its review

Published by DoAssignment. This reviewed lesson follows Ontario Grade 9 Science (SNC1W), expectation A1.3. It is a study resource, not an official curriculum publication.

Before publication, content is checked for structure, mathematical or chemical notation, calculations, course boundaries, and readability. Errors can still occur, so corrections are welcomed.

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