Question

8 mark for review
type of steel % carbon characteristics uses
low - carbon steel < 0.2 % malleable and ductile chains and nails
high - carbon steel 0.6 - 1.5 % hard and brittle cutting tools
the table above provides some information about two types of steel, both of which are alloys of iron and carbon. which of the following best helps to explain why high - carbon steel is more rigid than low - carbon steel?
a elemental carbon is harder than elemental iron.
b the additional carbon atoms within the alloy make the high - carbon steel less dense.
c the additional carbon atoms within the alloy increase the thermal conductivity of the high - carbon steel.
d the additional carbon atoms within the alloy make it more difficult for the iron atoms to slide past one another.

Explanation:

In an alloy like steel (iron - carbon alloy), rigidity is related to how easily atoms can move relative to each other. High - carbon steel has more carbon atoms. These additional carbon atoms disrupt the regular arrangement of iron atoms and make it harder for iron atoms to slide past one another, increasing the alloy's rigidity. Option A only compares the hardness of carbon and iron elements which is not directly related to the alloy's rigidity. Option B about density has no direct connection to rigidity. Option C about thermal conductivity is also not related to the mechanical property of rigidity.

Answer:

D. The additional carbon atoms within the alloy make it more difficult for the iron atoms to slide past one another.