Question

Read the lab procedure for a controlled experiment that looks at the effect of heat on the circumference of bicycle tires.

Step 1: Pump up six identical bike tires to the recommended air pressure.
Step 2: Place three tires under heat lamps, and keep the other three tires at room temperature.
Step 3: After four hours, measure the circumference of each tire.
Step 4: Record your results in the table.
Step 5: (?)

Which step should be next in this procedure?
List the materials that are needed.
Write a conclusion for the experiment.
Write a hypothesis for the results.
Draw a table for the observations.

Answer 1

Step 5 (next): Analyze the data — calculate the change in circumference for each tire, compute the average change for the heated group and for the control group, compare the averages, and draw a conclusion about whether heat affected tire circumference. Record any anomalies and possible sources of error.

Materials
- 6 identical bicycle tires (mounted on identical rims)
- Bicycle pump with pressure gauge
- 3 heat lamps (or other controlled heat source)
- Thermometer or temperature probe (to monitor lamp/room temperatures)
- Measuring tape or flexible measuring cord (for circumference) or string + ruler
- Stopwatch/timer (or clock) — for 4-hour timing
- Marker/labels to identify tires (H1–H3, C1–C3)
- Data sheet/clipboard and pen
- Safety equipment (gloves, eye protection, heat-resistant surface)
- Optional: pressure gauge to re-check tire pressure before and after

Hypothesis
If bicycle tires are heated for four hours, then the heated tires will have a larger circumference than the tires kept at room temperature, because increasing temperature will increase air pressure inside the tire and cause slight thermal expansion of the rubber and rim assembly.

Observation table (use this to record initial and final measurements)
You can print or copy this table and fill the numbers during the experiment.

| Tire ID | Condition | Initial circumference (cm) | Final circumference (cm) | Change (cm) | % Change | Notes |
|---------|-----------|---------------------------:|-------------------------:|-----------:|---------:|-------|
| H1 | Heated | | | | | |
| H2 | Heated | | | | | |
| H3 | Heated | | | | | |
| C1 | Control | | | | | |
| C2 | Control | | | | | |
| C3 | Control | | | | | |
| Average | Heated | | | | | |
| Average | Control | | | | | |

Notes on using the table:
- Measure and record the initial circumference immediately after pumping to recommended pressure (before turning on lamps).
- After 4 hours, measure final circumferences using the same method.
- Change = Final − Initial. % Change = (Change / Initial) × 100.
- Use the “Notes” column for things like visible deformation, leaks, temperature readings, or measurement uncertainties.

Conclusion (example wording you can use after collecting data)
The heated tires showed a small but consistent increase in circumference compared with the control tires, so the hypothesis is supported: heating caused a measurable increase in tire circumference. The likely reasons are increased air pressure inside the tire and slight thermal expansion of the rubber and rim. Sources of uncertainty include measurement error, uneven heating, possible small leaks, and not maintaining exactly equal initial pressures. To improve the experiment, monitor and record temperature and pressure continuously, increase the number of replicates, measure multiple times, and ensure uniform heating.