Science · Grade 7

Active learning ideas

Material Properties and Selection

Active learning helps students connect material properties directly to real-world structures. Hands-on testing and building make abstract concepts like tensile strength and density memorable. When students manipulate materials themselves, they notice trade-offs between properties in ways that lectures cannot replicate.

• Ontario Curriculum Expectations
• MS-ETS1-3

• 25–60 min
• Pairs → Whole Class
• 4 activities

Activity 01

• Decision Matrix
• 45 min · Small Groups

Testing Stations: Property Rotations

Prepare five stations: strength (drop weights on material spans), flexibility (hang weights on cantilever beams), density (submerge samples and measure displacement), durability (scratch or soak samples), conductivity (heat and touch). Small groups rotate every 7 minutes, record quantitative data like max load, and note observations.

Compare the suitability of steel, wood, and concrete for different structural applications.

Facilitation Tip

During Testing Stations: Property Rotations, assign small groups to one station first and rotate them through all others, ensuring they record observations in a shared table before moving on.

What to look for

Present students with three structural scenarios: a bridge support column, a bridge deck, and a suspension bridge cable. Ask them to select the best material (steel, wood, or concrete) for each and write one sentence explaining their choice based on material properties.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Activity 02

• Decision Matrix
• 60 min · Pairs

Bridge Build Challenge

Provide popsicle sticks, straws, tape, and string. Pairs design a 40 cm span bridge to hold the most books. Build prototypes, test loads, record failures, and redesign once based on property insights.

Analyze how material properties influence the overall strength of a structure.

Facilitation Tip

For the Bridge Build Challenge, provide only basic supplies at first and add constraints like limited weight or span length midway to push redesigns.

What to look for

Pose the question: 'If you were designing a playground swing set, what material would you choose for the frame and what for the seat, and why?' Facilitate a class discussion where students justify their choices using terms like strength, flexibility, and durability.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Activity 03

• Decision Matrix
• 30 min · Small Groups

Material Selection Debate

Assign materials to small groups. Each presents a case for using their material in a tower or bridge, citing tested properties. Class votes on best choice after Q&A.

Justify the choice of specific materials for building a lightweight, strong bridge.

Facilitation Tip

During the Material Selection Debate, assign roles (e.g., engineer, environmentalist, contractor) so students prepare arguments using specific material properties.

What to look for

Students receive a card with a material (e.g., steel, wood, concrete). They must write down two structural applications where this material is commonly used and one key property that makes it suitable for those uses.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

Activity 04

• Decision Matrix
• 25 min · Individual

Density Sink-or-Float Structures

Individuals build small boats from foil, wood scraps, clay. Test buoyancy by adding cargo. Calculate density ratios and discuss applications for floating bridges.

Compare the suitability of steel, wood, and concrete for different structural applications.

Facilitation Tip

In Density Sink-or-Float Structures, have students predict outcomes before testing and discuss why some structures float despite high density due to shape and air pockets.

What to look for

Present students with three structural scenarios: a bridge support column, a bridge deck, and a suspension bridge cable. Ask them to select the best material (steel, wood, or concrete) for each and write one sentence explaining their choice based on material properties.

• Analyze
• Evaluate
• Create
• Decision-Making
• Self-Management

A few notes on teaching this unit

Teachers often focus too much on listing properties without connecting them to function. Begin with a real structure students know, like a swing set, and ask what could go wrong if the wrong material is chosen. Avoid telling students which material is best; instead, guide them to discover trade-offs through testing. Research shows students retain concepts better when they fail first, then redesign, so embrace wobbly early prototypes as learning moments.

Successful learning looks like students discussing material choices with evidence. They should compare properties using accurate terms and adjust designs based on testing results. By the end, students justify selections with clear reasoning tied to structure function.

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Watch Out for These Misconceptions

• During Testing Stations: Property Rotations, watch for students assuming the hardest material is always the strongest.

  Have students test beams for bending under load and record both deflection and breaking point. Ask them to compare steel’s high tensile strength with wood’s ability to bend without snapping before selecting a 'best' material for a given scenario.

• During Bridge Build Challenge, watch for students insisting wood is better than steel because it is lighter.

  Provide a long span challenge and ask students to test thin wooden vs. steel beams. When wooden beams fail under load, guide them to discuss why steel’s tensile strength matters for long spans and how hybrid designs (e.g., steel cables with wooden decks) combine benefits.

• During Density Sink-or-Float Structures, watch for students thinking density alone determines whether a structure floats.

  Ask students to test solid cubes and hollow shells of the same material. Discuss how shape and air pockets lower overall density and improve buoyancy, connecting these ideas to real structures like boats or floating foundations.

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Methods used in this brief

• Decision Matrix