Video Transcript
Which of the following is not a property
of a solid? (A) Made of particles that are perfectly
still, (B) stable shape, (C) turns to liquid at its melting point, (D) made of particles that
are very close together, or (E) turns to gas at its sublimation point.
We can use particle theory to understand
the properties of solids. We can start with the fact that solids
have a fixed shape. This is explained by modeling a solid as
lots of individual particles. And there are attractive forces between
each particle that holds the shape together. But solids can only theoretically have
zero temperature. So even a really, really cold solid will
have some energy and the individual particles will be vibrating on the spot just a
little. So, on this basis, we’d expect the answer
to be made of particles that are perfectly still. Because we know that even if a solid is
very, very cold, the individual particles are going to have some small motion.
We know solids have a stable shape. And we know a melting point is when a
solid turns into a liquid. And we know that particles are very close
together because they’re touching. And they turn to gas at the sublimation
point, which is the temperature at which a solid turns directly into a gas without turning
into a liquid first. So, the item that’s not a property of a
solid is made of particles that are perfectly still.
