Number Density Calculator

Calculate Particle Concentrations with Precision

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Number Density Calculator

Calculate number of particles per unit volume.

Number Density: -

Molecular Density Calculator

Calculate molecular density from mass density and molar mass.

Molecular Density: -

Understanding Number Density

What is Number Density?

Number density (n) is the number of particles (atoms, molecules, or other entities) per unit volume. It's a fundamental quantity in:

  • Gas physics
  • Plasma physics
  • Materials science
  • Chemical kinetics

Relationship to Other Properties

Number density relates to other physical properties:

  • Mass density = n × particle mass
  • Pressure (ideal gas) = nkT
  • Mean free path ∝ 1/n
  • Collision frequency ∝ n

Applications

Number density is crucial in:

  • Semiconductor physics
  • Atmospheric science
  • Stellar astrophysics
  • Chemical reaction rates
  • Diffusion processes

Common Values

Typical number densities:

  • Air at STP: ~2.7 × 10²⁵ m⁻³
  • Metals: ~10²⁸-10²⁹ m⁻³
  • Semiconductors: ~10²³ m⁻³
  • Interstellar medium: ~10⁶ m⁻³

Essential Number Density Formulas

Basic Number Density

n = N/V

where N is number of particles and V is volume

Molecular Density

n = (ρNA)/M

where ρ is mass density, NA is Avogadro's number, M is molar mass

Ideal Gas Law

n = P/kT

where P is pressure, k is Boltzmann constant, T is temperature