The Physics
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# Density

## Summary

• Density is the ratio of mass to volume.
• Density is a measure of a material's or object's compactness.
• As a scalar quantity it has no direction.
• Density is a way to describe mass in a continuous system
 ρ = m V
• Units
• The SI unit of density is the kilogram per cubic meter [kg/m3].
• The Gaussian unit of density is the gram per cubic centimeter which is equivalent to a gram per milliliter [1 g/cm3 = 1 g/ml].
• One thousand kilograms per cubic meter equals one gram per cubic centimeter [1000 kg/m3 = 1 g/cm3].
• Specific gravity is the ratio of the density of a substance to the density of a standard substance.
• The standard substance is usually water for solids and liquids and air for gases.
• The density of liquid water under typical conditions on earth is approximately 1000 kg/m3.
• The density of air at room temperature near the surface of the Earth is approximately 1.2 kg/m3.
• Specific gravity is a unitless quantity.