A materials engineer is comparing the mechanical and electrical properties of pure…
CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
A materials engineer is comparing the mechanical and electrical properties of pure iron (Fe), an interstitial alloy of iron and carbon (steel), and a substitutional alloy of copper and zinc (brass). The engineer gathers the following macroscopic observations:
• Pure Fe bends easily before breaking and is a moderate electrical conductor.
• Steel is significantly harder and less malleable than pure Fe but retains similar electrical conductivity.
• Brass is softer than steel, highly malleable, and an excellent electrical conductor comparable to pure Cu.
Respond to the prompts below, using particulate-level reasoning that connects structure and properties.
(a) Describe how the presence and location of carbon atoms in steel modifies the metallic lattice of iron and explain why this change decreases malleability.
(b) Despite the structural change discussed in part (a), steel conducts electricity almost as well as pure iron. Explain this observation in terms of electron mobility.
(c) Compare brass with pure iron in terms of both malleability and electrical conductivity. Relate the differences to the nature of the substitutional alloy lattice.