Thanks for the question. You are correct. It is
called the meniscus, but let me give you
information on the subject.
A meniscus is
the curved surface at the top of a column of
liquid. In a science class, this liquid is usually
water or some sort of aqueous solution, and the
column is usually a graduated cylinder or a pipet.
As you may have noticed, when water is in such a
thin glass tube, it does not have a flat surface
at the top. Instead, the top is curved inward,
making it a little difficult to decide exactly
where to read the volume. The volume should be read
from the bottom of the meniscus.
doesn't water lie flat? Well, it has to do with
the nature of the water molecules and glass
molecules themselves. Water is made up of
polar molecules, which have positively and
negatively charged ends. Since opposites attract,
the positive sides attract the negative sides, and
all of the molecules stick to one another. This is
why water droplets can form. Glass molecules also
happen to be polar. Again, since polar molecules
like to stick together, the water in a glass tube
will actually tend to stick to the sides of the
tube! You can see this at the top of the graduated
cylinder, where the water will slightly creep up
the sides and form a curve, which is the meniscus.
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