Two identical beakers each contain 50 mL of liquid water at 25 °C
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Two identical beakers each contain 50 mL of liquid water at 25 °C.
• Beaker 1 is sealed with an airtight lid.
• Beaker 2 is left open to the atmosphere.
In both beakers, the masses of liquid water and of water vapor in the headspace are monitored over a period of 24 h.
(1) Describe qualitatively how the mass of liquid water is expected to change in each beaker over the 24-h period, and use these observations to determine whether each system reaches equilibrium.
(2) For Beaker 1, explain at the particle level why measurable evaporation and condensation continue to occur after the mass of liquid water has stopped changing.
(3) For Beaker 2, propose one experimental modification (other than sealing the beaker) that would allow the liquid–vapor system to attain equilibrium, and justify how your modification accomplishes this.