MCAT Basics (from MedSchoolCoach) Gas Phase
Jun 17, 2025
Join MCAT instructor Alex Starks as he unravels the intricacies of gas-phase chemistry. With years of experience, he explains the physical properties of gases, highlights the ideal gas law, and clarifies the ABCD laws. Alex delves into how conditions like temperature and pressure affect molecular collisions and discusses the significance of the Van der Waals equation in understanding real gas behavior. He also provides essential takeaways to help you ace that tricky gas section on the exam!
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Gas Behavior At Macro And Micro Scales
- Gases have no fixed shape or volume and expand to fill available space at the macroscopic level.
- Microscopically, gas particles are far apart, move very fast, and act nearly independently.
Use Kelvin And Know STP
- Work gas problems using Kelvin for absolute temperature and use 273 K as 0°C reference point.
- Remember standard pressure is 1 atm (760 mmHg) and 1 mole gas occupies 22.4 L at STP.
Mercury Barometer Thought Experiment
- Alex describes a mercury barometer thought experiment with an inverted tube and a vacuum above it to show how atmospheric pressure pushes mercury up the tube.
- He explains the mercury stops rising when its weight balances atmospheric push, not because internal pressure equals atmosphere.