Vapor Pressure and Heat of Vaporization Investigations
Recommended for grades 9–16.
When a volatile liquid is added to a closed container such as an Erlenmeyer flask, it will evaporate into the air above it in the container. Eventually, equilibrium is reached between the rate of evaporation and the rate of condensation. At this point, the vapor pressure of the liquid is equal to the partial pressure of its vapor in the flask.
In the Preliminary Activity, you will determine the vapor pressure of ethanol at room temperature using a Gas Pressure Sensor and a Temperature Probe. You will first measure air pressure at room temperature. You will then add ethanol to the flask and, once equilibrium has been established, measure the total pressure exerted by air and ethanol vapor. You will then subtract air pressure from the total pressure to determine the vapor pressure of ethanol at that temperature.
After completing the Preliminary Activity, you will first use reference sources to find out more about vapor pressure before you choose and investigate a researchable question dealing with vapor pressure.
Sensors and Equipment
This investigation requires each of the following Vernier sensors and equipment (unless otherwise noted):
Step-by-step instructions for the Preliminary Activity
List of materials and equipment
Note: The experiment preview of the Preliminary Activity does not include essential teacher information, safety tips, or sample data. Instructions for Logger Pro and other software (such as LabQuest App or TI handheld software, where available) are on the CD that accompanies the book. We strongly recommend that you purchase the book before performing experiments.