A student is conducting an experiment to determine what factors affect the vapor pressure of methanol. The student is measuring the vapor pressure of methanol using a mercury manometer, as pictured below. The experimental apparatus has an evacuated 1.0 liter bulb, into which the student injects a measured amount of methanol.
The methanol then vaporizes to a gas until the vapor pressure equilibrates with the liquid, by saturating the bulb volume with methanol vapor. The temperature of the methanol is controlled by placing it in a water bath. The student measures the vapor pressure by determining the height of the mercury column after the methanol is injected.
Experiment 1 Results
The student first tried varying the volume of methanol injected into the bulb.
Experiment 2 Results
Next, the student tried varying the temperature of a fixed volume of methanol. The student made sure there was always methanol liquid in the glass bulb when the measurement of vapor pressure was taken.
Experiment 3 Results
Finally, the student tried measuring the vapor pressure of different substances, both with and without alcohol $(-OH)$ groups, at $20° C$.
Which of the following changes to the experimental setup would not have changed the results of Experiment 2?