Video Transcript
As the temperature increases, what
is the correct order in which the substances shown below become gradually softer and
easier to shape? (A) Lump of sulfur, bar of metal,
rubber ball. (B) Bar of metal, rubber ball, lump
of sulfur. (C) Lump of sulfur, rubber ball,
bar of metal. (D) Rubber ball, lump of sulfur,
bar of metal. (E) Rubber ball, bar of metal, lump
of sulfur.
The question shows three very
different substances. We have sulfur, metal, and
rubber. We are told that as the temperature
increases, the three substances soften in different ways. And we need to list the substances
in order of increasing softness as the temperature gets hotter.
Firstly, let’s look at how these
substances are different. This is a bar of a solid metal. Metals all tend to behave in a
similar way when heated. Most metals are solids at room
temperature and are hard. Also, they only soften at high
temperatures. In other words, when a metal is
hot, it is softer and then it is easier to shape.
When a metal is softened by
heating, they can be more easily hammered and rolled. So we can shape hot metals easily
into thin flat sheets by hammering or rolling. And we can stretch metals into
long, thin wires more easily at high temperatures. But if the temperature gets too
hot, metals melt and turn into liquid metal. This happens at their melting
point. Every metal has its own specific
melting point.
Now let’s look at rubber. Rubber, for example, this rubber
ball, is a solid substance, which is naturally rather soft even at room
temperature. We can easily shape rubber at
normal everyday temperatures. Rubber is already soft. For example, it is easy to squeeze
a rubber ball with your hand. We don’t need to heat rubber up to
soften it.
What about the substance
sulfur? Sulfur is a solid, nonmetal
substance at room temperature. This nonmetal does not soften even
when it is heated and its temperature increases.
The temperature axis shows that
rubber is naturally soft, metals only soften at high temperatures, and sulfur does
not soften even at very high temperatures. So the correct order in which the
substances soften and become easier to shape as the temperature increases is (E):
rubber ball, bar of metal, lump of sulfur.
