Flashcards: Phase Diagrams

A scientist prepares an experiment to demonstrate the second law of thermodynamics for a chemistry class. In order to conduct the experiment, the scientist brings the class outside in January and gathers a cup of water and a portable stove.

The temperature outside is –10 degrees Celsius. The scientist asks the students to consider the following when answering his questions:

Gibbs Free Energy Formula:

ΔG = ΔH – TΔS 

 

Liquid-Solid Water Phase Change Reaction:

H2O(l) ⇌ H2O(s) + X

The scientist prepares two scenarios. 

Scenario 1:

The scientist buries the cup of water outside in the snow, returns to the classroom with his class for one hour, and the class then checks on the cup. They find that the water has frozen in the cup.

Scenario 2: 

The scientist then places the frozen cup of water on the stove and starts the gas. The class finds that the water melts quickly.

After the water melts, the scientist asks the students to consider two hypothetical scenarios as a thought experiment. 

Scenario 3:

Once the liquid water at the end of scenario 2 melts completely, the scientist turns off the gas and monitors what happens to the water. Despite being in the cold air, the water never freezes.

Scenario 4:

The scientist takes the frozen water from the end of scenario 1, puts it on the active stove, and the water remains frozen.

Which of the following best describes the Liquid-Solid Water Phase Change Reaction above?

Aqueous redox reaction

Physical reaction

Both an aqueous redox and physical reaction

Both a chemical and physical reaction

Chemical reaction

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The Medical College Admissions Test (MCAT) often looms in the distance as a frightening prospect to aspiring medical students. At the end of sophomore collegiate studies, the MCAT begins to close in quickly. Juggling an enormous class load, extracurricular activities, and athletics can make it seem like there is no time to prepare! Whether you need MCAT tutoring in AtlantaMCAT tutoring in Houston, or MCAT tutoring in San Francisco, working one-on-one with an expert may be just the boost your studies need.

In 2015, test anxiety may seem even more severe because the MCAT has been completely changed. For years, the test has been the same, consisting of three main sections: Physical Sciences, Biological Sciences, and Verbal Reasoning. The 2015 revision may leave students feel as if the rug has been pulled out from under them, but the new MCAT’s Chemical and Physical Foundations of Biological Systems section is actually not so different from the Physical Sciences section of years past. 

Nevertheless, the test’s revision does require some modifications in your approach for preparation. In years past, the Physical Sciences section would ask questions that demanded an understanding of how physics and chemistry worked in mechanical systems, so it was sufficient to study physics and chemistry in conceptual isolation. In contrast, the 2015 MCAT is expecting test-takers to apply these mechanical principles to biological systems. No longer is it adequate to understand the ideal gas law by itself; you must now appreciate how the ideal gas law explains alveolar gas exchange in the lungs. Varsity Tutors offers resources like free MCAT Physical Sciences Practice Tests to help with your self-paced study, or you may want to consider an MCAT Physical Sciences tutor.

In this way, the 2015 MCAT’s Chemical and Physical Foundations of Biological Systems demands a different approach than the memorization you may be used to in classes like organic chemistry. Now, you are being asked to master the content and then apply that content to novel systems. The MCAT wants to make sure that you don’t just know material, but that you understand its application.

This approach to learning advanced-level science can serve you well in future years. In medical school, the information is far too substantial to memorize. Instead, you must understand the context and the importance of each idea, as well as the relationships of one idea to others. Forming these interacting ideas into a cohesive view of biology can help lead to success in medical school. It is no coincidence, then, that this is the same set of skills being emphasized on the 2015 MCAT. 

With this appreciation of the new Chemical and Physical Foundations of Biological Systems section, it should be clear that the abundance of resources available for the MCAT of years past still offer value today. The material it covers remains relatively unchanged; it is just testing this material with a different approach and different kinds of questions. As you review, you need to understand abstract ideas, not simply memorize discrete facts. Varsity Tutors’ free MCAT Physical Sciences Flashcards can help you do that. Our MCAT Physical Sciences Flashcards test your knowledge by asking questions drawn from all of the categories that the MCAT Physical Sciences section covers. A full explanation of how to arrive at the correct answer accompanies each flashcard, making it easy to identify any subtle, abstract misunderstandings well before they can trip you up on test day. Plus, you can review anywhere at any time; our MCAT Physical Sciences Flashcards are available through the Learning Tools website or the Varsity Tutors app. In addition to the MCAT Physical Sciences Help Section and MCAT Physical Sciences tutoring, you may also want to consider using some of our MCAT Physical Sciences Diagnostic Tests

Undoubtedly, preparing for the new MCAT requires a different approach than previous years. You may experience greater anxiety due to continuously developing expectations of what you’ll see on test day. Overcoming this anxiety and mastering the concepts being tested can help you begin on a path to success in medical school and as a physician.

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