### Video Transcript

Which of the following statements
could not be used to describe nanoparticles? (A) Particles one to 100 nanometers
in size. (B) Particles that are smaller than
most atoms. (C) Particles with a high
surface-area-to-volume ratio. (D) Particles with different
properties than those of the same material in bulk. (E) Particles containing a few
hundred atoms or ions.

We are asked which statement does
not describe nanoparticles. Let’s start by discussing what a
nanoparticle is. Nanoparticles are particles of
matter that are between one and 100 nanometers in diameter. These are very small particles
indeed. A nanosized particle could fit into
a box 100 by 100 by 100 nanometers. Answer option (A) does correctly
describe nanoparticles, and so we can rule it out. Nanoparticles come in a variety of
shapes, including cubic structures called nanocubes, spherical nanospheres, and even
nanotubes. These tiny structures usually
contain a few hundred atoms or ions. And so we can rule out answer
option (E) as the statement does describe nanoparticles.

We can immediately see that answer
option (B), particles that are smaller than most atoms, does not make sense. If nanoparticles consist of several
hundred atoms or ions, then they cannot be smaller than most atoms. The statement does not describe
nanoparticles. To be sure, let’s rule out answer
options (C) and (D) as well. For any object, such as particles,
we can calculate a surface area as to volume ratio. Small particles will have a large
ratio, and large particles, a small ratio. Let’s clear some space to prove
this.

If we compare small particle one by
one by one with a big particle 10 by 10 by 10, the volume of the small particle is
one times one times one, and for the big particle 10 times 10 times 10, which gives
one unit cubed for the small particle and 1000 units cubed for the big particle. The surface area of the small
particle will be six, because there are six sides, multiplied by the area of one
side, which is one times one, which gives six units squared. In a similar way, the surface area
of the large particle is six multiplied by 10 times 10, which is 600 units
squared. For each particle, we can now put
these values into a ratio. And if we remove the units for
simplicity, for the small particle, we get six as to one, and for the large
particle, 600 as to 1000. If we simplify the ratio for the
large particle, we get 0.6 as to one.

Can you see that the small particle
has a large ratio and the bigger particle has a smaller ratio? We can rule out answer option (C),
particles with a high surface-area-to-volume ratio, as this statement does describe
these tiny nanoparticles. Nanoparticles are a hot topic in
science. Because of their tiny size and very
high surface-area-to-volume ratio, they have very different properties than a bulk
piece of the same material. This is the reason why
nanoparticles interest scientists so much. We can rule out answer option (D)
as this statement does correctly describe nanoparticles.

Finally, which statement could not
be used to describe nanoparticles? The answer is (B) particles that
are smaller than most atoms.