Kompressibilitätsforschung

Kompressibilität, or compressibility, is a measure of how a material’s volume changes in response to pressure. It is defined as the negative fractional change in volume with respect to pressure. In thermodynamics, the isothermal compressibility k_T is defined by k_T = - (1/V) (∂V/∂P)_T, while the adiabatic compressibility k_S = - (1/V) (∂V/∂P)_S. The reciprocal of k_T is the bulk modulus, B = 1/k_T, which characterizes a substance’s resistance to uniform compression.

Compressibility depends on the material and its state. Liquids typically have small compressibilities, making them relatively incompressible, while gases exhibit large compressibilities, with volume changing appreciably under modest pressures. Solids generally possess very low compressibilities, though thermal or pressure effects can modify their response.

For fluids, the bulk modulus relates to sound propagation by B = ρ c^2, where ρ is density and c is the speed of sound. More broadly, isothermal and adiabatic compressibilities reflect how volume responds to pressure at constant temperature or constant entropy, and they differ due to thermal effects.

Measurement and application: Compressibility is determined through ultrasonic methods, volumetric P–V–T experiments, or analyses of equation-of-state data. It is a key parameter in engineering, geophysics, and materials science, informing predictions of deformation, wave transmission, and stability under load. In water at room temperature, the isothermal compressibility is about 4 to 5 × 10^-10 Pa^-1, illustrating its relatively low compressibility compared with many gases.