Experimental design and analysis (LAB)
Estimating absolute zero with a sealed sample of air
- Unit 9
- 10 points
- About 27 minutes
You can use a calculator on this question, just like on exam day.
A two-part lab question. First you design an experiment to answer a question: what you change, what you measure, the equipment and how you would analyze the data. Then you get a data table from a similar experiment, choose what to graph (often so the points fall on a straight line), plot it and use the slope, the intercept or the graph's shape to answer a question. On the exam: Question 3 of 4. New for May 2027: the free-response section is 95 minutes, down from 100, for all 4 questions (50% of your score), one of each type in this order. Calculator and equation sheet allowed. The CED suggests 25–30 minutes. This question type started in May 2025, so Physics 2 free-response questions from 2024 and earlier are built differently.
The question and its sources
Students want to estimate the value of absolute zero on the Celsius scale using a fixed sample of air.
Part A: Available equipment
A rigid, sealed metal sphere filled with air and connected by a short tube to a pressure gauge, a thermometer, a large container, ice, water, and a hot plate that can heat the water.
Source: Hypothetical lab setup
Part B: Table 1. Another group's data (same sealed sphere of air)
| Temperature T (°C) | Pressure P (kPa) |
|---|---|
| 0 | 95.1 |
| 20 | 101.9 |
| 40 | 108.9 |
| 60 | 115.6 |
| 80 | 122.8 |
Source: Hypothetical data
Suggested time: 27 minutes
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Part (A(i))
3 pointsDescribe an experimental procedure you could use, with only the equipment listed in Part A, to collect data that would allow you to estimate absolute zero in degrees Celsius. Include what you would measure, what you would change, and any steps you would take to reduce experimental uncertainty.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (A(ii))
2 pointsDescribe how you would use your data to estimate absolute zero. Include what you would graph and how you would use the graph.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (B(i))
1 pointUsing the ideal gas law, explain why the graph of pressure versus Celsius temperature should be a straight line, and why the temperature at which the line reaches zero pressure is absolute zero.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (B(ii))
2 pointsUsing the data in Table 1, plot pressure versus temperature and draw a best-fit line. You can't draw here, so describe the graph you would draw: what goes on each axis (with units), the scale, the points you would plot, and the best-fit line.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
Part (B(iii))
2 pointsUse your best-fit line to calculate an experimental value for absolute zero in degrees Celsius.
Type math plainly, like x^2, sqrt(x) or (x+1)/(x−1).
0 / 2,500 characters
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