Density is a representation of the mass of an object based on its volume. It is commonly expressed in grams per cubic centimeter. Water has a density of 1 g/cm^3. Densities are typically calculated by determining the weight and volume of an object and then dividing the volume into its weight.
Things You'll Need
 Scale
 Calipers

Weigh a penny on a scale that can provide accurate results down to a milligram. Note that the weight should be made in grams.

Measure the diameter and thickness of the penny with calipers that can give results in centimeters.

Calculate the volume of the penny in cubic centimeters by multiplying the thickness by the surface area. The surface area is calculated by using the formula pi x r^2, where r is the radius, which is one half of the diameter.

Divide the weighed mass of the penny in grams by the calculated volume. This will result in the density in grams per cubic centimeter.
References
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