How Would You Define Relative Density?
Relative density, also known as specific gravity, is a dimensionless quantity representing the ratio of a substance's density to the density of a reference material. This comparison allows us to understand how dense a substance is relative to a known standard.
The core concept of relative density hinges on comparing the mass of a specific volume of a substance to the mass of an equal volume of a reference substance. The reference material is typically water for liquids and solids, and air for gases. Because it's a ratio of densities, the units cancel out, resulting in a unitless value.
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Formula: Relative Density = (Density of substance) / (Density of reference material)
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Example: If the density of gold is 19.3 g/cm³ and the density of water is 1 g/cm³, the relative density of gold is 19.3. This means gold is 19.3 times denser than water.
Practical Applications
Relative density finds use in various fields:
- Material Science: Determining the purity or composition of materials.
- Geotechnical Engineering: Assessing the properties of soils and their compaction.
- Chemical Engineering: Analyzing fluid properties and mixtures.
- Medicine: Measuring the concentration of substances in bodily fluids.
Reference Materials
The choice of reference material depends on the substance being measured:
- Liquids and Solids: Water (at a specific temperature, usually 4°C) is the standard.
- Gases: Air (at standard temperature and pressure) is often used.
Several sources define relative density as the ratio of the density of a substance to the density of a reference material. This ratio is unitless, emphasizing the comparative nature of this property. The reference material is commonly water for solids and liquids, and air for gases. ( Byjus.com, Wikipedia, ThoughtCo, Chegg.com )
