Teach lesson
Thermal Expansion: comparing metals with real video evidence
Students use the Thermal Expansion remote lab to compare aluminum, copper, and brass, then separate direct observations from model-based claims.
Learning Outcomes
Use the linear expansion model to predict how materials should compare.
Use the remote lab to observe at least two material runs.
Record direct video and screen-gauge evidence without inventing unavailable exports or automatic alpha values.
Use reference coefficient values to make a bounded model-based prediction.
Write a claim-evidence-reasoning conclusion that states a limitation.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
Frame the model
8 min
When a solid is heated, its particles vibrate more and the average spacing between particles can increase slightly. For a long metal rod, that tiny change can be described with a linear expansion model.
The model is useful, but it is not the same as direct evidence. In this lab you can directly choose a material and watch a real heating run. The screen view can show instrument values, including a digital displacement gauge in millimeters, but those are frame-read video observations rather than a clean data export or an automatic alpha value. Alpha is the linear-expansion coefficient, a material property used in the model. Record a value only when it is legible, include units, and label uncertainty.
Thermal expansion remote setup
The remote lab shows real recorded equipment runs for selected metal rods.
Linear expansion model
Use the model to decide what evidence you would need for a fair comparison. Reference coefficients are introduced later for analysis, not as direct lab readings.
Linear expansion model
\Delta L = \alpha L_0 \Delta T
In the equation, what does alpha, the linear-expansion coefficient, represent?
Before opening the lab, predict which of aluminum, brass, and copper should expand the most for the same original length and same temperature change. Use the model and these reference alpha values in your explanation: aluminum 23 x 10^-6 1/C, brass 19 x 10^-6 1/C, and copper 17 x 10^-6 1/C.
Plan a fair comparison
9 min
To compare materials fairly, change the material and keep the observation procedure the same. Watch each run from the beginning to the end, record the same kinds of evidence, and label each row as your own lab run or a teacher-provided comparison row.
Material choices
The lab configuration screen lets you choose the material for the heating run.
Investigation workflow
Use the same observation workflow for every material so the comparison is fair.
Which plan best tests whether material affects thermal expansion?
Write your plan for the lab. Name which materials you will try, what you will watch for in the front view and screen/gauge view, and how you will keep the comparison fair. For the compact route, explain which row could be teacher-provided.
Collect video evidence
18 min
Open the lab from this activity and use the same observation procedure for every material you compare. For the 55-minute route, run aluminum, copper, and brass. For the compact route, run at least two materials live and use one clearly labelled teacher-provided comparison row so the table still compares all three materials.
Open the Thermal Expansion lab
Choose a material: aluminum, copper, or brass.
Start the observation and let the video run to the end.
Record what you can directly see in the front view and screen view.
For the displacement gauge, use the first readable frame before or at the start of heating and the final readable frame at the end. If either value is not legible, write "not legible" in the note instead of estimating.
Repeat with the other assigned material(s) using the same procedure.
Do not invent an automatic alpha value or clean exported data table.
Evidence boundary
High-quality evidence includes a clear boundary between observation and inference.
Observation evidence table
Enter one row for aluminum, copper, and brass. In the compact route, at least two rows should come from your own live lab runs and the third may be a clearly labelled teacher-provided comparison row. In the screen/gauge column, include start/end gauge values only if they are legible; otherwise write not legible. Do not invent automatic alpha values or a clean data export.
| Material | Evidence origin | Front-view observation | Screen/gauge observation | Elapsed time s | Limitation or uncertainty |
|---|---|---|---|---|---|
Video evidence record
Attach a screenshot, short notes file, student-made table, or shared evidence summary showing the material runs you used.
Which statements can you honestly support from this lab when the evidence is visible or labelled? Select all that apply.
Interpret with a bounded model
12 min
Now compare your observations with the reference model. If your video evidence is mostly qualitative, say that clearly. A careful scientist can still make a useful claim, but the claim must match the evidence.
Use these reference coefficients as model values only:
- aluminum: 23 x 10^-6 1/C
- brass: 19 x 10^-6 1/C
- copper: 17 x 10^-6 1/C
Which order is predicted for the same original length and temperature change?
Explain why a reference-model calculation using alpha, original length, and temperature change is not the same as a direct alpha measurement from the lab video. Name the direct measurements that would be missing or uncertain.
Write the scientific claim
8 min
Your final answer should be direct, evidence-based, and honest about limits.
Write a claim-evidence-reasoning conclusion. Include:
- your claim about how material affects expansion;
- at least one observation from your own run;
- one comparison with the reference model;
- one limitation that prevents overclaiming;
- if you used screen-gauge values, a note that they were read from video frames.
Optional model extension
15 min
Optional calculation: use the reference model only, change in length = alpha x original length x temperature change. If an aluminum rod has original length 0.50 m, temperature change 40 C, and alpha 23 x 10^-6 1/C, what is the predicted change in length in millimeters? Show the substitution, compute the result in meters, multiply by 1000 to convert to millimeters, and round to two decimal places.
Optional follow-up: if you were designing a stronger lab, what extra instrument or readout would you add so students could calculate alpha from direct measurements, and what quantity would it measure?
Using the reference values, estimate the predicted length change for brass and copper for the same original length, 0.50 m, and temperature change, 40 C. Then compare them with aluminum and decide whether the difference would be easy to read reliably from a video/gauge.