Nernst

Walther Hermann Nernst (1864–1941) was a German physicist and chemist whose work significantly advanced thermodynamics and electrochemistry. He is best known for laying the theoretical foundations that connect energy, temperature, and chemical change, and for developing practical tools used to quantify electrochemical processes.

In thermodynamics, Nernst formulated what is often called Nernst’s theorem, or the third law of thermodynamics. The theorem states that the entropy of a perfect crystal approaches zero as temperature approaches absolute zero, and it implies the unattainability of absolute zero by any finite sequence of processes. This work provided a rigorous basis for calculating absolute entropies and understanding phase transitions at very low temperatures. He also contributed to thermochemistry by linking heat, energy, and chemical reactions in a quantitative framework.

In electrochemistry, Nernst derived the Nernst equation, which relates the electric potential of an electrode to temperature and the activities or concentrations of reacting species. The equation is fundamental for determining redox potentials and for interpreting electrochemical measurements. He also helped develop the Nernst–Planck equation, which describes the flux of ions under the influence of concentration gradients and electric fields in electrolytes.

Nernst’s contributions were recognized with the Nobel Prize in Chemistry in 1920 for his work in thermochemistry. His theories and equations remain central to physical chemistry, influencing disciplines from materials science to electrochemical sensing and energy storage.