Return to MCAT® Blog
Homepage
MCAT Chemistry Question — Meniscus
- by
- Oct 28, 2014
- MCAT Question of the Day
- Reviewed By: Liz Flagge
A student observes that mercury forms a convex meniscus in the graduated cylinder but that water forms a concave one. This behavior is best explained by the fact that:
A) the two liquids are being kept in graduated cylinders made of different materials.
B) the adhesive forces between water and the walls of the graduated cylinder are greater than the adhesive forces between the mercury and the walls of the graduated cylinder.
C) the cohesive forces between two mercury atoms are stronger than the cohesive forces between two water molecules.
D) the mercury has stronger cohesive than adhesive forces, whereas water has stronger adhesive than cohesive ones.
Explanation
The shape of the meniscus lets you know whether the substance has more attractive force for itself (convex meniscus) or for the walls of the cylinder (concave meniscus). Water, for example, experiences more adhesion between the water and the walls of the container, thus “pulling” the water up the sides of the container creating a concave meniscus. The adhesive force is greater than the cohesive force between the water molecules. The opposite is true for mercury, thus making (D) the right answer.
A: While this may be true, the student’s observation doesn’t lead to this conclusion.
B, C: The shape of the meniscus doesn’t let you compare the forces in water to the forces in mercury directly. It only lets you compare one force (adhesion) to another force (cohesion) for one substance.
Want more MCAT practice?
We’ve got options for every schedule and learning style!
From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!
Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT expert using the form below. No obligation, just expert advice.
Related Posts
Search the Blog
Free Consultation
Interested in our Online MCAT Course, One-on-One MCAT Tutoring or Med admissions packages? Set up a free consultation with one of our experienced Senior Student Advisors.
Schedule NowPopular Posts
-
-
MCAT Blog What's on the MCAT? -
-
-
MCAT Blog How to Review MCAT Full Lengths
Free MCAT Practice Account
Need great MCAT practice?Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.
Learn More