Density Lab

Density of a Penny

Results and Discussion 2

A Penny is an inhomogenous mixture zinc and copper, with a center of zinc covered by a layer of copper. Each metal can be considered a pure element. The density of a penny, then, should be a weighted average of the densities of zinc (7.13 g/ml) and copper (8.96 g/ml), closer to copper if the penny is mostly copper, and closer to zinc if the penny is mostly zinc. For example, if the penny were 25% Zinc and 75% Copper, the density of the penny would be:

Density = (0.25)(7.13 g/mL) + (0.75)(8.96 g/mL) = 8.50 g/mL

As you can see, this density is closer to the density of the Copper (8.96 g/mL) than it is to Zinc (7.13 g/mL).

Predict the density of a penny if it were 50% Zn and 50% Cu.