Wax is a collective term for organic compounds that are malleable solids near room temperature. These substances are typically composed of long-chain hydrocarbons, esters, or fatty acids. Density is a fundamental physical property, defined as the mass of a substance contained within a specific unit of volume. For wax, density is not a fixed number but falls within a predictable range.
Understanding Density in the Context of Wax
Density measures how tightly matter is packed, expressed mathematically as mass divided by volume (D=m/V). Wax density is not constant because it is a mixture of compounds, not a single pure substance. Different types of wax, such as those derived from petroleum or plants, have varied chemical compositions, meaning their molecules pack together with different efficiencies.
The long hydrocarbon chains that make up waxes have varying lengths and branching structures. These molecular differences directly influence the crystalline structure of the solid wax, affecting how much mass fits into a cubic centimeter.
Temperature also plays a significant role. As wax is heated, thermal energy causes molecules to spread farther apart, increasing the overall volume. This thermal expansion results in a lower density for the liquid form compared to its solid state.
Specific Density Values of Common Waxes
The density of solid wax is typically measured at room temperature and is expressed in grams per cubic centimeter (g/cm³).
Paraffin wax, derived from petroleum, exhibits a density range of approximately 0.88 to 0.94 g/cm³. This range exists because paraffin is a blend of various hydrocarbon chains, and its density is affected by its refinement level and oil content.
Beeswax, a natural product created by honeybees, generally demonstrates a slightly higher density than most paraffin types, typically falling between 0.95 and 0.97 g/cm³ at standard temperatures. This greater density is due to its complex composition, which includes long-chain esters, fatty acids, and various hydrocarbons.
Soy wax, a popular plant-based alternative created by hydrogenating soybean oil, has a solid density often reported in the range of 0.85 to 0.90 g/cm³. This makes soy wax comparable to many paraffin grades, related to its primary components being triglycerides. A decrease in density is observed as any of these waxes transition into their molten, liquid form.
Why Wax Floats: Density Compared to Water
The practical outcome of these density values is demonstrated when wax is placed in water, where it almost always floats. This phenomenon is governed by the principle of buoyancy, which dictates that an object will float if its density is less than the density of the fluid it displaces. The density of pure water at standard temperature is very close to 1.0 g/cm³.
When comparing the densities of common waxes to water, nearly all of them are found to be less dense. For instance, paraffin (0.88 to 0.94 g/cm³) and beeswax (0.95 to 0.97 g/cm³) are both substantially lighter than water. Even the densest common waxes are still only about 97% as dense as water, ensuring they remain buoyant.
This difference in density means that a given volume of wax weighs less than the same volume of water. This allows the wax to be supported by the water’s upward buoyant force. The principle applies regardless of the specific wax type, as virtually all waxes used in common products have densities below the 1.0 g/cm³ threshold of water.