Density is a fundamental physical property that defines the mass per unit volume of a material. In the context of materials science, it plays a key role in determining how a substance interacts with its environment, influences mechanical properties, and determines its suitability for specific applications. Density is one of those properties that determines everything from object buoyancy to the stability of chemical reactions and engineering buildings.
For ease of use, Alfa Chemistry has a table of densities of common materials that lists the densities of the most ordinary materials you will find in your life.
| Materials | Density (g/cm3) |
| Water | 997 |
| Air | 1.23 |
| Ice | 920 |
| Glass | 2500 |
| Boron carbide | 2520 |
| Graphite | 2260 |
| Carbon fiber | 2000 |
| Polyethylene | 950 |
| Polypropylene | 900 |
| Carbon dioxide | 2 |
| Brick | 1700 |
| Porcelain | 2400 |
| Tungsten carbide | 14500 |
| Diamond | 3500 |
| Graphene | 2270 |
| PET | 1350 |
| Polycarbonate | 1200 |
| Carbon monoxide | 1.14 |
| Sand | 1500 |
| Limestone | 2750 |
| Elektron 21 | 1800 |
| Duralumin | 2780 |
| Zirconium-tin alloy | 6560 |
| Austenitic stainless steel | 7850 |
| Mild steel | 7850 |
| Gray iron | 7150 |
| TZM alloy | 10220 |
| Inconel | 8200 |
| ETP | 8890 |
| Cupronickel | 8940 |
| Zamak 3 | 6600 |
| Ruby | 3980 |
| Uranium dioxide | 10970 |
| Polystyrene | 1050 |
| Polyvinyl chloride | 1330 |
| Nitrous oxide | 2 |
| Concrete | 2400 |
| Granite | 2750 |
| Pure titanium | 4510 |
| 6061 alloy | 2700 |
| Zirconium-niobium alloy | 6560 |
| Martensitic stainless steel | 7650 |
| High-carbon steel | 7850 |
| White iron | 7770 |
| Mo-25 Re alloy | 11200 |
| Hastelloy | 8890 |
| Brass | 8530 |
| Aluminium bronze | 7640 |
| Soft tin solder | 8600 |
| Salt | 2200 |
| Kevlar | 1440 |
| Polyamide-Nylon | 1140 |
| Rubber | 1100 |
| Methan | 0.657 |
| Stone wool | 20 |
| Quartz | 2650 |
| Ti-6Al-4V | 4500 |
| 7068 alloy | 2850 |
| Chromoly steel | 7850 |
| Duplex stainless steel | 7800 |
| Tool steel | 7810 |
| Ductile iron | 7300 |
| Tungsten-rhenium alloy | 19700 |
| Stellite | 8690 |
| Bronze | 8770 |
| Beryllium copper | 8250 |
| Amalgam | 14000 |
| Sugar | 1600 |
| Wax | 960 |
| Coal | 1400 |
| Asphalt concrete | 2360 |
| Propane | 2 |
| Glass wool | 20 |
| Aerogel | 10 |
| Rose gold | 12900 |
| Yellow gold | 15500 |
| White gold | 15900 |
| PH stainless steel | 7750 |
| High-speed steel | 8160 |
| Malleable iron | 7150 |
| Pure tungsten | 19250 |
| Invar | 8100 |
| Constantan | 8860 |
| Nickel silver | 8690 |
| Galistan | 6440 |
| Oak wood | 704 |
| Pine wood | 500 |
| Gasoline | 755 |
| Diesel fuel | 850 |
| Acetylene | 1.1 |
Definition and Mathematical Basis of Density
Density is defined as the mass per unit volume of a substance and is represented mathematically as:
Where:
- ρ is the density (in kg/m3 for SI units, lbm/ft3 for imperial units),
- m is the mass of the substance, and
- V is the volume of the substance.
The standard unit for density in the International System of Units (SI) is kilograms per cubic meter (kg/m3), whereas, in imperial measurements, it is expressed as pounds mass per cubic foot (lbm/ft3). This simple yet essential property is crucial for numerous calculations across scientific disciplines, including chemistry, physics, engineering, and material science.
How do temperature and pressure affect density?
Density is not a constant; it varies with changes in external conditions, primarily temperature and pressure. As temperature increases, most materials experience thermal expansion, which leads to a decrease in density. This phenomenon occurs because the average kinetic energy of atoms increases, causing them to move apart. The expansion of materials due to heating is quantified using the linear or volumetric thermal expansion coefficients. In contrast, cooling typically leads to contraction and a corresponding increase in density.
Conversely, increasing pressure tends to compress a material's volume, thereby increasing its density. This effect is more pronounced in gases, which are highly compressible, than in solids or liquids. The relationship between pressure, volume, and density in gases can be described by the ideal gas law:
PV = nRT
Where:
- P is pressure,
- V is volume,
- n is the number of moles of gas,
- R is the universal gas constant,
- T is temperature.
This explains why high-pressure environments, such as those found deep within the Earth or in industrial processes, result in denser materials.
What Does Density Mean in Real Life?
Identifying density is critical to many applications, from the selection of high-density materials such as osmium for industrial purposes to lighter materials such as aluminum for spacecraft. Additionally, by knowing about the impact of temperature and pressure on density, engineers can design systems that work well under various environmental influences.
In pharmaceuticals, for example, fine-tuning the density of molecules can dictate the outcome of chemical reactions, material handling, and formulation design. When an industry is committed to delivering high-quality chemicals, knowing the density of these compounds is important for consistency and manufacturing efficiency.
In environmental science, density is important for observing how pollutants behave across different environments, like how contaminants can diffuse in the water or build up in the atmosphere. In a similar manner, density is a crucial factor in buoyancy, a cornerstone of naval design, and helps vessels and submarines stay in the water.
