Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of GraphSearch.
Concept
Dulong–Petit law
Summary
The Dulong–Petit law, a thermodynamic law proposed by French physicists Pierre Louis Dulong and Alexis Thérèse Petit, states that the classical expression for the molar specific heat capacity of certain chemical elements is constant for temperatures far from the absolute zero.
In modern terms, Dulong and Petit found that the heat capacity of a mole of many solid elements is about 3R, where R is the universal gas constant. The modern theory of the heat capacity of solids states that it is due to lattice vibrations in the solid.
Experimentally Pierre Louis Dulong and Alexis Thérèse Petit had found in 1819 that the heat capacity per weight (the mass-specific heat capacity) for 13 measured elements was close to a constant value, after it had been multiplied by a number representing the presumed relative atomic weight of the element. These atomic weights had shortly before been suggested by John Dalton and modified by Jacob Berzelius.
Dulong and Petit were unaware of the relationship with R, since this constant had not yet been defined from the later kinetic theory of gases. The value of 3R is about 25 joules per kelvin, and Dulong and Petit essentially found that this was the heat capacity of certain solid elements per mole of atoms they contained.
The Kopp's law developed in 1865 by Hermann Franz Moritz Kopp extended the Dulong–Petit law to chemical compounds from further experimental data.
Amedeo Avogadro remarked in 1833 that the law did not fit the experimental data of carbon samples. In 1876, Heinrich Friedrich Weber, noticed that the specific heat of diamond was sensible to temperature.
In 1877, Ludwig Boltzmann showed that the constant value of Dulong–Petit law could be explained in terms of independent classical harmonic oscillators. With the advent of quantum mechanics, this assumption was refined by Weber's student, Albert Einstein in 1907, employing quantum harmonic oscillators to explain the experimentally observed decrease of the heat capacity at low temperatures in diamond.
Official source
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.