Video Transcript
Alloys of a particular metal
display lower malleability. Which of the following properties
is also likely to be lower in these alloys? (A) Density, (B) ductility, (C)
hardness, (D) melting point, (E) strength.
An alloy is a metallic solid
solution that contains at least two different types of elements. Alloys of a metal tend to have
different properties than a pure metal does. In this case, the alloy has a lower
malleability than the pure metal.
Malleability is the ability of a
material to be hammered or pressed into different shapes or thin sheets. This occurs because the addition of
an alloying element disrupts the regular lattice that we see in a pure metal. So, it’s much harder for atoms in
an alloy to slide past each other. Let’s look through our answer
choices to see which property is also likely to be lower in the alloy.
The density of an alloy will be
different than that of a pure metal, depending on the alloying element used. However, alloys with both a higher
and lower density can have lower malleability. So, we wouldn’t know if the density
is lower in the alloy described by this question. So, we can eliminate answer choice
(A).
Ductility describes the ability of
a material to be drawn into wires. Alloying affects ductility for the
same reason we saw with malleability. The presence of the alloying
element disrupts the metal lattice, making it harder to draw the metal into
wires. So, we would expect an alloy with
lower malleability to have lower ductility. So, (B) must be the correct answer,
but let’s take a look at the other answer choices so we make sure we understand the
material.
If a material has low malleability,
it will be difficult to hammer it into different shapes. So, we would expect the material to
be quite hard and strong. In other words, we expect the
hardness and strength of the alloy to be higher, not lower. So, answer choices (C) and (E)
aren’t correct.
The melting point is affected by
alloying, but it doesn’t increase or decrease consistently. For example, pure copper metal has
a melting point of 1085 degrees Celsius. If we look at the melting points of
some copper alloys, brass and cupronickel, we can see that brass has a lower melting
point than copper, but cupronickel has a higher melting point than copper. Both brass and cupronickel would
have lower malleability than copper. So, we can’t expect the melting
point to be lower just because the malleability is lower.
So, the only property we would
expect to be lower for alloys of a metal that display lower malleability is
ductility. Answer choice (B) is the correct
answer.