Save the Toy Bridge

Overview

A toy bridge has broken, and students must investigate which adhesive or mixture could make the strongest paper chain to repair it. They predict, test and compare PVA glue alone, PVA with tissue, PVA with sand, glue stick and flour paste. Students identify the changed variable, keep other conditions fair, record results and discuss why results may vary.

Learning intentions

Students will:

• recognise that materials can be physically changed or combined for a purpose
• investigate how different glues and mixtures affect a paper chain
• identify what is changed and what must stay the same in a fair test
• record observations, count paper clips and represent class results on a graph
• compare predictions and observations, then suggest a further question

Success criteria

• I can name the glue or mixture I tested.
• I can explain what we changed and what we kept the same.
• I can make a prediction, follow safe steps and record observations.
• I can count the paper clips my chain holds and compare my result with others.
• I can use evidence to describe what happened without claiming one mixture must always win.

Vocabulary

Material, mixture, adhesive, PVA glue, flour paste, tissue, sand, predict, fair test, variable, observe, strength, evidence, result.

Curriculum links

• Materials and physical changes: students explore how actions and mixtures change materials and how materials can be used for a purpose.
• Planning and conducting investigations: students suggest and follow safe procedures while testing a prediction.
• Recording and representing data: students complete a table, count paper clips and help construct a class column graph.
• Comparing observations: students compare predictions and group results, consider fairness and suggest a further question.

Lesson structure (50 minutes)

1. 0–5 min · Story hook and question. Open with the toy bridge rescue hook and show a picture of a broken toy bridge. Explain that the class must test paper chains to help repair it, then ask: “Which glue or mixture might make the strongest chain, and how could we test it fairly?” Students share ideas with a partner and identify what “strongest” could mean.

2. 5–11 min · Predict and plan. Display the prediction and fair-test slides and introduce the five test materials: PVA alone, PVA mixed with small tissue pieces, PVA mixed with a small amount of sand, glue stick and flour paste. Distribute the glue challenge recording sheet. Students circle or draw a prediction and complete the planning sentence: “I think ___ will hold the most paper clips because ___.” Discuss the changed variable: the glue or mixture. Establish controls: same paper strips, same strip size, same amount of adhesive, same chain design, same drying or setting time and the same testing method.

3. 11–16 min · Demonstration and safety. Demonstrate making one paper link, joining links in the same design and hanging a cup or tray to add paper clips one at a time. Model the recording table and explain that a fair test changes one thing at a time. Students suggest safety rules: no tasting or touching eyes, use tools carefully, keep sand and glue away from mouths, wipe spills, and wash hands after the investigation.

4. 16–31 min · Group investigation. Organise five groups of five, assigning each group one adhesive or mixture and roles of materials manager, builder, clip counter, recorder and reporter. Provide identical strips and a measured amount of the assigned adhesive. Students build a paper chain using the same number and design of links, allow the agreed setting time, then add paper clips one at a time until the chain breaks or a link opens. They record the number held, observations such as sticky, gritty, flexible or stiff, and any problems. Photograph results if a tablet is available. Remind groups to repeat the test if time allows, using the same procedure.

5. 31–41 min · Class results graph. Return to the results graph slide. Invite each group to report its result; record results in a class table and construct a simple column graph, with adhesive or mixture along the bottom and number of paper clips up the side. Students add their group result to the worksheet, compare it with their prediction and discuss whether groups using the same mixture obtained exactly the same result.

6. 41–47 min · Conclusion and fair-test discussion. Ask: “What evidence helps us answer the question?” and “Was our test fair?” Students use the sentence frame, “Our chain held ___ paper clips. We predicted ___. The result was ___.” Discuss that results may vary because of link size, adhesive amount, joining, setting time or testing technique. Emphasise that today’s result does not prove one mixture must always be strongest. Students suggest a further question, such as “Would the result change with fabric or thicker paper?”

7. 47–50 min · Reflection and exit check. Students complete the final section of the glue challenge recording sheet: draw or write one result, name one control and explain one safety rule. Conduct a quick show of fingers—one finger for “I need help”, two for “I understand some”, three for “I can explain the fair test”—and collect sheets.

Resources

• the toy bridge rescue and investigation deck
• the glue challenge recording sheet
• Identical paper strips, pre-cut to the same size
• PVA glue, tissue pieces, clean sand, glue sticks and flour paste
• Small cups or trays, paper clips and measuring spoons
• Mixing containers and craft sticks
• Aprons or table coverings, wipes and handwashing facilities
• Five group result cards or a whiteboard for the class table and graph
• Tablets or camera, if available

Prepare the flour paste with flour and water before the lesson. Use only a small amount of sand and tissue. To make drying fair, either use a short, clearly timed setting period for every group or provide teacher-prepared chains made with the same materials, quantities and setting time for the testing stage.

Assessment

• During planning, check that students can identify the changed variable and at least two conditions that must stay the same.
• During group work, observe safe handling, role participation, accurate counting and whether students follow the same testing procedure.
• Use the worksheet, class graph and exit check to assess prediction–result comparisons, observations, evidence-based conclusions and a suggested further question.

Differentiation

• Support students with picture labels for each adhesive, a completed example row, sentence starters and a partner scribe. Read the worksheet instructions aloud and allow drawing or oral responses.
• Provide pre-measured adhesive and pre-cut strips for students who need reduced motor or organisational demands. Keep sand in containers and assign a non-mixing role where sensory needs require it.
• Pair EAL/D students with supportive peers and demonstrate “same”, “different”, “holds” and “breaks” with actions and real materials.
• Extend confident students by calculating the difference between their prediction and result, comparing repeated trials, or designing a follow-up fair test using a new paper type.