Video Transcript
Which of the following is the term
used to refer to the energy of an object due to the energy of its constituent
particles? A) Chemical energy, B) Nuclear
energy, C) Internal energy, D) Electric potential energy.
All right, so what we want to do is
figure out which of these four terms correctly describes the kind of energy that an
object has due to the energy of its constituent particles. That is, the particles that make
that object up. To figure this out, a good place to
start is with the nucleus of an atom. Let’s say that here is our nucleus,
a collection of protons and neutrons. Just considering this nucleus all
by itself, there’s a form of energy stored here called nuclear energy. This is energy that’s possessed by
the protons, we’ve drawn them in blue, and the neutrons, we’ve drawn them in green,
due to the forces that they exert on one another in this nucleus.
Nuclear energy comes not from the
energy of the protons and neutrons by themselves, but because of the forces they
exert on one another. Therefore, we wouldn’t say that
nuclear energy is the energy an object has due to the energy of its constituent
particles. In the case of nuclear energy, it’s
the interactions between those particles that are important. So, we’ll cross that off our list
of candidates. Moving on, let’s draw a few
electrons around this nucleus, as they normally would appear for an uncharged
atom.
Now, these electrons, which are
negatively charged, feel an attractive force to the positively charged protons in
the nuclear core. And it works both ways; the protons
are attracted to the electrons too. And then, the negatively charged
electrons push one another away or repel each other, as do the positively charged
protons to one another. We can say then that this atom,
just by virtue of having positive and negative charges in it, possesses some
electric potential energy.
Now, in general, electric potential
energy describes energy that is stored in electrically charged objects. An important thing to notice about
the term is that it’s strictly a potential energy. That is, it’s not energy associated
with motion. But if we consider our problems
statement again and talking about these constituent particles, the particles that
make up our object of interest, these particles could have potential as well as
kinetic energy. And based on this description, we
want our term to be able to account for them both. So, considering option D, electric
potential energy, because this only accounts for a potential and not kinetic energy,
we won’t choose this as our answer.
And then, getting back to our atom,
when we talk about the electrical potential energy of the charges in an atom, that’s
a description of that atom’s chemical energy. We could say that the term electric
potential energy applied to the charges in an atom is equivalent to the chemical
energy of that atom. This means that option A, chemical
energy, is also a description of potential but not kinetic energy types. Therefore, it, too, offers an
incomplete description of the energy of an object due to the energy of its
constituent particles, which may involve kinetic energy. This means we’ll cross option A off
our list as well.
And we’re left with one remaining
choice, internal energy. If we were to model our atom, shown
here as a single dot like this. And then, if we were to collect
lots of these atoms together and enclose them in some container. Then at that point, if we were to
add up all the energy of each one of these atoms, both the kinetic and the potential
energy of each one. Then, that sum would be the energy
of these constituent particles. And we could say that these
constituent particles are the atoms that make up our object. And that is indeed our object’s
internal energy. This is the term that refers to the
energy of an object due to the energy of its constituent particles, the particles
that make it up.
