MCAT Basics Podcast

Gas Phase

Alex Starks talks about Gas-Phase Concepts for the MCAT. He dissects the different gas properties, the ideal gas law and expounds on the ABCD laws of gases.

  • [01:03] Physical Properties of Gases
  • [05:28] The Ideal Gas Law
  • [08:26] Conditions that Promote Molecular Collisions in Gases
  • [09:35] The ABCD laws of Gases
  • [16:05] Important Takeaways
  • Physical Properties of Gases

    When preparing for your MCATs, one of the topics that are often overlooked is the gas phase. Alex explains that having a basic understanding of gases for the MCATs is crucial when boosting your odds of success. This is because you can meet straight-up questions on gas laws and how gases behave in the MCAT. That said, the first thing you need to understand is that gasses have no fixed shape or volume and that gas laws are calculated using the Kelvin scale. Moreover, the standard temperature of all gases is 273 Kelvin, which is equivalent to 0┬░Celcius. The other gas condition which you know of is that the standard mercury barometer is calibrated such that 1 atmosphere of pressure will push the mercury up by 760 mm.

    When you combine these two standard conditions, you realize that ideal gases occupy 22.4 L per mole of molecules. This implies that a mole of gas can only be contained in a smaller container if we play around with either temperature or pressure.

    The Ideal Gas Law

    The most important thing you should concentrate on when preparing for the MCAT is how gases behave. However, the gas laws that we talk about relate to ideal gases only. An ideal gas is a hypothetical gas whose molecules occupy negligible space, have no potential energy, and obey gas laws. The following assumptions better describe ideal gases.

    1. Gases are comprised of particles with no definite volume but have definite mass
    2. The collisions occurring between gas particles and between gas particles and a container are entirely elastic, meaning that neither molecule lose energy.
    3. Kinetic energy is identical for all gases at a given temperature, regardless of gas type.
    4. There are no intermolecular forces acting between the molecules or their surroundings
    5. The molecules are constantly in continuous random motion.

    Alex Starks

    Alex is the Associate Director of MCAT at MedSchoolCoach. Alex scored in the 99th percentile on his MCAT and has more than 13 years of teaching experience. Midway into 2021, he took over the reigns as the host of the MCAT Basics podcast.

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