Zinc is a common metallic element, identified by the symbol Zn and atomic number 30. Its intrinsic characteristics are defined by its physical properties, which are attributes that can be observed or measured without changing the substance’s chemical identity. Understanding these characteristics is the basis for its widespread use in numerous industrial applications, from construction to battery production.
Visual Characteristics and Atomic Arrangement
At room temperature, zinc is a solid metal exhibiting a bluish-white or silvery-gray color and a metallic luster when freshly exposed. It is relatively dense, with a density of approximately 7.14 grams per cubic centimeter (g/cm³) at 20°C.
Zinc’s physical behaviors are rooted in its atomic structure. It crystallizes in a Hexagonal Close-Packed (HCP) structure, where each atom is surrounded by twelve others, creating a dense packing efficiency. This specific crystalline lattice influences how the metal deforms under stress.
Response to Heat and Temperature
Zinc has a relatively low melting point compared to many common metals, melting at about 419.5°C. This low temperature is a factor in its use in die-casting and manufacturing processes. The metal transitions into a gaseous state at its boiling point of approximately 907°C.
The metal’s capacity to absorb heat is quantified by its specific heat, which is about 0.382 kilojoules per kilogram-Kelvin (kJ/kg·K) at 20°C. Zinc also exhibits a noticeable rate of thermal expansion, meaning its volume increases as its temperature rises.
Malleability and Mechanical Strength
Zinc’s mechanical behavior is highly dependent on temperature. At room temperature, the metal is notably hard and brittle, meaning it tends to fracture rather than bend when subjected to mechanical stress.
The HCP crystal structure contributes to this brittleness because there are limited ways for the atomic layers to slide over each other. However, when zinc is heated slightly, its mechanical properties change dramatically.
Above approximately 100°C, zinc becomes significantly more malleable and ductile, allowing it to be rolled into thin sheets or drawn into wire. This makes hot-working an important industrial technique for shaping the metal.
If the temperature is raised above 200°C, the metal becomes brittle again. This secondary brittle phase means that it can be easily pulverized by hammering at these elevated temperatures. Zinc’s relative hardness is moderate, registering around 2.5 on the Mohs scale.
Conductivity of Electricity and Heat
Zinc is classified as a good conductor of both electrical current and thermal energy. The metal’s electrical conductivity is due to the presence of free electrons that can move easily through the metallic lattice. Its electrical conductivity is approximately \(1.7 \times 10^7\) Siemens per meter (S/m).
While it conducts electricity well, zinc is significantly less efficient than highly conductive metals such as copper or silver. For example, copper’s conductivity is more than three times higher than that of zinc. This moderate conductivity, combined with its chemical reactivity, makes zinc suitable for use as an electrode in certain battery types, such as zinc-carbon and alkaline batteries.
The ability to transmit heat is also strong, with a thermal conductivity value of about 113 to 120 Watts per meter-Kelvin (W/(m·K)). This thermal property is a result of the same free electrons that facilitate electrical flow.