Copper is generally denser than brass. This difference arises because copper is a pure metallic element, while brass is an alloy, or mixture, of copper and another metal. Although they have a similar appearance, their distinct compositions lead to differences in their physical properties.
Defining “Heavier”: Understanding Density
The determination of which material is heavier depends on density, which is the amount of mass contained within a specific volume. Density measures how tightly the material’s matter is packed together, calculated as mass divided by volume. When comparing materials, it is important to consider equal volumes, such as a cubic centimeter of one material versus another. For instance, if you held a one-inch cube of pure copper and a one-inch cube of brass, the copper cube would feel heavier. Density values are typically expressed in units like grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).
The Role of Composition in Density
Copper’s greater density is a direct result of its composition as a pure element with a consistent atomic structure. Pure copper (Cu) has a fixed density of approximately 8.96 g/cm³ at room temperature.
Brass, by contrast, is an alloy primarily composed of copper and zinc. The density of zinc is significantly lower than copper, measuring about 7.14 g/cm³. When zinc is mixed into copper to create brass, the overall density of the resulting alloy is reduced. Depending on the exact percentage of zinc added, the density of brass typically ranges between 8.4 g/cm³ and 8.7 g/cm³. The more zinc present in the brass alloy, the lower the final density will be.
Where the Density Difference Matters
The small but measurable difference in density between copper and brass plays a role in material selection across various industries. In applications requiring high mass in a small space, such as ballasts, counterweights, or certain specialized electrical connectors, the higher density of pure copper is often preferred. Using copper ensures the maximum possible weight is achieved without increasing the component’s physical size.
However, the lower density of brass can be advantageous in other scenarios. For components where the superior machinability of brass is desired, an alloy may be chosen. Though copper is renowned for its electrical conductivity, its density is also a factor in electrical wiring, where engineers must balance the material’s mass with its conduction properties.