2040 – 03 – Defining Density

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If you know a metal’s mass, then you can figure out its density. Density refers to the size and closeness of the molecules that compose a material; it’s the mass-per-unit volume. A high density means that an object is tightly packed with molecules. Pound cake, for example, has high density, while angel food cake has lower density.

A common figure used in manufacturing is the strength-to-weight ratio. It compares the density of a metal to its strength. This comparison shows the value of a metal’s strength relative to its price, which usually depends on its weight.

Titanium, for example, has a high strength-to-weight ratio: it weighs less than other metals, but can perform equally well under similar conditions. This makes it the ideal metal to use when building aircraft, or in other lightweight, high-strength products.