temperaturedependence

Temperature dependence describes how a property or process varies as temperature changes. It is a fundamental aspect of physical systems because thermal energy alters molecular motion, reaction barriers, phase stability, and material structure. Properties may vary with temperature in ways that reflect intrinsic material behavior or external conditions, and are often described by empirical data or theoretical models.

In chemistry and chemical engineering, reaction rates typically increase with temperature, frequently described by the Arrhenius equation k = A exp(-Ea/(RT)). Viscosity generally decreases with rising temperature, while the solubility of most solids in liquids increases; the solubility of gases in liquids usually decreases as temperature rises.

In solid-state physics and materials science, the electrical resistivity of metals tends to rise with temperature due to increased lattice scattering, whereas semiconductors show temperature-dependent band gaps and carrier concentrations. The band gap often narrows as temperature grows. Thermal expansion causes materials to change dimensions with temperature, quantified by the coefficient of thermal expansion. Diffusion coefficients generally increase with temperature.

Phase transitions occur at characteristic temperatures, such as melting and boiling points, or critical points in fluids. In superconductors, electrical resistance vanishes below a critical temperature. Biological systems also exhibit temperature-dependent rates, with enzymes having optimum ranges and reaction rates frequently characterized by temperature coefficients such as Q10.

Understanding temperature dependence is essential for design, modeling, and interpretation across science and engineering, and requires careful consideration of measurement conditions and reference frames.