Video Transcript
The figure describes the structure
of molecules in a very low-temperature solid. What is the structure of these
molecules if they do not gain or lose any energy?
Let’s begin by looking at the
provided figure. Each circle represents a
molecule. We know that the figure represents
a solid. In a solid, the molecules move
slowly. Each molecule stays mostly in one
position as it vibrates. There are strong forces of
attraction between molecules in a solid.
An intermolecular force of
attraction is a force of attraction between particles. In this problem, the particles are
molecules. A force of attraction is a force
that pulls particles closer together. Since the forces between molecules
in a solid are very strong, the molecules are very close together and cannot move
away from one another. We are told that the solid is at a
very low temperature. We need to find out what will
happen to the structure of the molecules in the solid if they do not gain or lose
any energy.
If a solid absorbed energy, its
molecules would move faster. If enough energy was absorbed, the
forces of attraction would weaken and the molecules could move more freely and get
farther apart. If the molecules absorb enough
energy, the solid could change to a liquid. Our drawing of the molecules in a
liquid looks a lot like figures A and B. So these two figures show what
might happen if the solid gains enough energy to become a liquid. So these two options cannot be
correct.
We want to know what the structure
of the molecules will be if they do not gain or lose any energy. Answer choices (C) and (E) cannot
be correct either. In these figures, it’s clear to see
that the molecules have moved to new positions. But solid particles generally stay
in the same positions unless enough energy is added. Figure D must be the correct
answer. In this figure, all the molecules
in the solid are in the same positions, which would be true if we haven’t added any
energy.
In conclusion, the figure that
shows the structure of the molecules in a low-temperature solid if they do not gain
or lose energy is answer choice (D).
