# Number density (Relation to Mass density)

## Description

Number density is an intensive quantity used to describe the degree of concentration of countable objects. For atoms or molecules of a well-defined molecular mass M, the number density can be expressed in terms of the mass density of a substance. ( Molecular mass or molecular weight refers to the mass of a molecule. It is calculated as the sum of the mass of each constituent atom multiplied by the number of atoms of that element in the molecular formula.)

Related formulas## Variables

n | Volume number density (m^{-3}) |

N_{A} | Avogadro constant |

M_{1} | Molar mass of one constituent (kg/mol) |

M_{2} | Molar mass of the other constituent (kg/mol) |

m_{1} | Mass of one constituent (kg) |

m_{2} | Mass of the other constituent (kg) |

V | The total volume (m^{3}) |