Name the soft, dense blue-gray metal whose greatest use is in car batteries.

• A. Iron
• B. Tin
• C. Lead
• D. Aluminum

Answer: (C)

Lead is a soft, dense blue-gray metal that can be formed into sturdy plates, which is essential for car batteries that endure repeated charging and discharging. In a lead-acid battery, these lead plates react with sulfuric acid to create reversible chemical reactions that store energy; during discharge, the lead and the sulfuric acid chemistry produce lead sulfate, and charging reverses this process. This combination—a malleable metal that holds up well in an acidic, rugged environment and supports repeated chemical changes—explains why lead is used so widely in car batteries. The other metals don’t fit as well: iron is strong and prone to corrosion, tin isn’t used for automotive battery plates at scale, and aluminum is lightweight and forms an oxide layer that hinders the long-cycle durability needed for car batteries.