The method and the results are on the kinetic theory of gases lab. Do the analysis yourself first, then check the answers below.
Quick answer: Gas pressure is caused by particles colliding with the walls of their container. These answers go with the Physics 9-10 lab on kinetic theory of gases: the graph, the calculations, the uncertainties and the conclusion explained, for all 8 analysis questions.
Here are the kinetic theory of gases lab answers for physics grades 9-10: graph, calculations, uncertainties and conclusion. First do the lab yourself, then compare, and go back to the lesson if needed.
Model answers use the sample table. Your own numbers will differ slightly, but p × V should stay constant within a few percent. Notice how the straight line through the origin on the p against 1 / V graph is stronger evidence than a single curve.
Level: Physics grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: IGCSE 2.1, HS-PS3-2
Largest difference = 5040 − 5020 = 20 (or 5050 − 5040 = 10). 20 / 5040 × 100 = 0.4 %. The product is constant within experimental error.
Question 3 Graph shape
p against V is a downward curve (a hyperbola). p against 1 / V is a straight line through the origin, because p = constant × (1 / V).
Question 4 Gradient
Gradient = (251 − 101) / (0.0500 − 0.0200) = 150 / 0.0300 = 5000 kPa cm³. It represents the constant value of p × V (about 5000 kPa cm³).
Question 5 Prediction
p = 5040 / 15 = 336 kPa.
Question 6 Control of temperature
Compressing gas does work on it and warms it. A fast push would raise the temperature and break the condition of constant temperature. Waiting lets the gas cool back to room temperature.
Question 7 Source of error
The real volume is V + 2, so the true product is p (V + 2). The recorded product pV is smaller than the real one and is not exactly constant; the effect is largest at small V. A graph of p against 1 / (V + 2) would be straighter.
Question 8 Conclusion and improvement
Pressure is inversely proportional to volume for a fixed mass of gas at constant temperature, since p × V stays constant within 0.4 %. Improvement: use a longer waiting time, a larger range of volumes, or repeat each reading and average.
