10 Differences Between density and relative density

Difference between Density and Relative Density

Difference between Density and Relative Density

What is Density?

Density is a fundamental concept in physics and materials science that refers to the amount of mass an object has per unit volume. It is a measure of how much matter is packed within a given space.

Examples of Density:

1. The density of water is approximately 1 g/cm³.

2. Iron has a density of about 7.86 g/cm³.

3. The density of air is much lower than that of water, approximately 0.0012 g/cm³.

Uses of Density:

1. Density is used to identify substances. Each material has a characteristic density that can help in its identification.

2. It is used in engineering and construction to determine the strength and stability of structures.

3. Density plays a crucial role in buoyancy, explaining why objects float or sink in fluids.

What is Relative Density?

Relative density, also known as specific gravity, is the ratio of the density of a substance to the density of a reference substance (usually water). It provides a measure of how dense a substance is compared to another substance.

Examples of Relative Density:

1. The relative density of gold is approximately 19.3, meaning it is 19.3 times denser than an equal volume of water.

2. Cork has a relative density of less than 1, which means it floats in water.

3. The relative density of air is close to 0.0012, indicating that it is less dense than water.

Uses of Relative Density:

1. Relative density is used in various industries, such as the petroleum industry, to characterize and analyze substances.

2. It helps in determining the purity of liquids by comparing their densities to those of known pure substances.

3. Relative density is crucial in the brewing industry, where it is used to measure the sugar content of liquids during fermentation.

Differences Table:

Difference Area Density Relative Density
Definition The amount of mass per unit volume of a substance. The ratio of the density of a substance to the density of a reference substance.
Comparison Comparison is made within the same substance. Comparison is made between different substances.
Reference Point No reference substance is required. Uses a reference substance, often water.
Unit Common units include g/cm³, kg/m³, and lb/ft³. It is a ratio and, therefore, has no unit.
Representation Usually represented by the symbol “ρ”. Usually represented by the symbol “SG” or “RD”.
Comparative Analysis Different substances with the same density can have different relative densities. Substances with the same relative density will have the same density ratio regardless of the actual density.
Applications Used in various fields including physics, engineering, and manufacturing. Used in specific industries such as petroleum, brewing, and medicine.
Measurement Accuracy It provides direct information about the mass per unit volume. It helps in comparing densities and identifying the concentration or purity of a substance.
Significance Important for studying the behavior of materials under certain conditions. Allows for comparisons and classifications of substances based on their densities.
Calculation The mass and volume of the substance are measured or determined. The density of the substance and that of the reference substance are measured or determined.


Density and relative density are related concepts used to describe the density of substances. Density refers to the mass per unit volume of a substance, while relative density compares the density of a substance to a reference substance. The key differences lie in the comparison method, reference point, representation, and measurement applications.

People Also Ask:

  1. What is the purpose of measuring density?
  2. Density measurement helps in identifying substances, determining structural stability, and understanding buoyancy phenomena.

  3. How is relative density different from specific gravity?
  4. Relative density is the ratio of a substance’s density to water, whereas specific gravity is the ratio of a substance’s density to that of a reference substance.

  5. What factors affect the density of a substance?
  6. Temperature, pressure, and molecular composition can affect the density of a substance.

  7. Why is density important in engineering?
  8. Density is crucial in engineering as it helps determine the strength and stability of materials and structures.

  9. Can density be negative?
  10. No, density cannot be negative as it is a measure of mass divided by volume, both of which are positive quantities.

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