Materials & Prep
Prepare identical cups or small containers, warm water that is safe to handle, cardboard, foil, cotton balls, tape, thermometers, and a timer. Set a starting temperature of about 40°C and use the same water volume for each team. Copy a simple design record with spaces for starting temperature, ending temperature, temperature change, criterion, evidence, proposed change, and redesign result. Confirm warm-water and thermometer procedures against school safety expectations.
Opening
Ask“A paper airplane misses the target to the left. What could you change on the next attempt, and what did the miss tell you?” Students first make an individual prediction, then compare answers with a partner. Accept responses such as changing the fold, angle, or force when they connect the change to the observed miss.
ConnectThe miss is not a bad grade or the end of the design. It is information about what to change next. Engineers use evidence from a test to improve a design. Today, the test will be measurable: teams will improve a container that keeps warm water from cooling.
Direct instruction
IntroduceThe design criterion is “After five minutes, the water temperature drops by 5°C or less.” A team calculates temperature change by subtracting the ending temperature from the starting temperature. A smaller drop means better insulation.
Worked exampleDisplay this sample record: starting temperature 40°C, ending temperature 34°C, temperature change 40 - 34 = 6°C. Since 6°C is greater than 5°C, the first design does not meet the criterion. Do not simply say “add more material.” The evidence says the design allowed too much heat to escape, so I choose a change that could slow heat transfer. For example, I place cotton balls around the cup, use cardboard to hold it in place, and keep foil on the outside as a reflective layer. In a second sample test, the starting temperature is 40°C and the ending temperature is 36°C, so the change is 4°C. The redesign meets the criterion.
ConfrontA failed test is not evidence that the designer is bad. It is evidence about the design. Also, a lower ending temperature is not better. Students must compare the amount of temperature change, not just whether a thermometer reading “looks high.”
Check for understandingShow the result 39°C to 33°C after five minutes. Students show or say whether the design meets the criterion and explain why. Expected response: “No. The drop is 6°C, so it misses the 5°C-or-less criterion.”
Guided practice
ModelDemonstrate one possible first design without presenting it as the correct design. Each team receives the same amount of warm water in an identical container. The container is the object being insulated. Cardboard, foil, cotton balls, and tape are the available design materials.
Have studentsIn teams of three, assign a builder, measurer, and recorder. Plan and build one first design. The recorder writes the prediction and the exact materials and arrangement before testing. Teams should not copy a teacher-approved “best” design because the purpose is to learn from their own evidence.
ScaffoldGive students this planning frame: “Our starting temperature is __°C. We predict the ending temperature will be __°C because __. We will place __ around __. We will measure __ after five minutes.” Students who need a concrete entry point may begin with cotton balls around the container, then choose where cardboard or foil will go and explain that choice.
CirculateAsk, “What part of your design is your evidence-based change?” and “What measurement will tell you whether it worked?” Check that teams use the same timing and record both temperatures.
Independent work or discussion
StudentsTest the first design for five minutes, record the starting and ending temperatures, calculate the temperature drop, and compare it with the 5°C criterion. Teams then identify one specific weakness or opportunity from the result and redesign. They must change at least one feature and write: “Our result was __°C of cooling. We changed __ because __.”
StudentsRetest the redesign for five minutes using the same water volume, starting temperature as closely as possible, and test time. Record the second result and decide whether the redesign improved, stayed the same, or became less effective. If time or water availability prevents a full second test, teams may use the provided sample comparison data, but they must still justify the change from their own first-test evidence.
Look forStudents using “it failed” without identifying what the measurement showed, changing several features without being able to explain any one change, or treating more material as automatically better. Prompt them to name the result, the change, and the reason. Extension: Teams whose redesign meets the criterion should improve it again while using less material, then explain the tradeoff between insulation, material use, ease of construction, and reliability.
Closing
DiscussInvite two teams to report different first-test results and the changes those results led to. Ask the class whether the design with the most materials must be the best design. Require evidence from temperature change rather than opinions.
Exit ticketStudents complete three sentences independently: “Our first design changed by __°C and did/did not meet the criterion because __. We changed __ because the test showed __. The redesign was better, worse, or the same because its temperature change was __°C compared with __°C.” Collect the design records and exit tickets as evidence that students used a measurable test to improve a first design.