Hiukkasmäärätiheys

Hiukkasmäärätiheys, often translated as particle number density or number density, is a measure used in physics and chemistry to quantify the number of particles within a given volume. It is defined as the total number of particles divided by the volume they occupy. The standard unit for particle number density in the International System of Units (SI) is particles per cubic meter (m⁻³).

This concept is widely applied in various scientific disciplines. In thermodynamics and statistical mechanics, it's crucial for describing the state of gases, liquids, and solids. For instance, the density of gas molecules in a container directly influences its pressure and temperature. In astrophysics, particle number density is used to characterize interstellar and intergalactic media, as well as the composition of stellar atmospheres. In materials science, it helps to understand the properties of semiconductors and other solid-state materials by quantifying the concentration of charge carriers or dopants.

Particle number density is distinct from mass density, which relates mass to volume. While related, they describe different aspects of a substance. For example, a gas with a high particle number density might still have a low mass density if the individual particles are very light. The calculation of particle number density is straightforward: if you have N particles in a volume V, the number density n is given by n = N/V.