Hukum termodinamik pertama: Perbezaan antara semakan

Ia seingsering digambarkan melalui kenyataan bahawa dalam proses termodinamik peningkatan dalam tenaga dalaman sesuatu sistem menyamai dengan peningkatan haba yang dibekalkan kepada sistem, tolak peningkatan kerja yang dilakukan oleh sistem pada persekitarannya.<ref>Clausius, R. (1850). Ueber de bewegende Kraft der Wärme und die Gesetze, welche sich daraus für de Wärmelehre selbst ableiten lassen, ''Annalen der Physik und Chemie'' (Poggendorff, Leipzig), '''155''' (3): 368-394 [http://gallica.bnf.fr/ark:/12148/bpt6k15164w/f384.image].</ref><ref>Rankine, W.J.M. (1850). On the mechanical action of heat, especially in gases and vapours. ''Trans. Roy. Soc. Edinburgh'', '''20''': 147-190.[http://www.archive.org/details/miscellaneoussci00rank]</ref><ref>Helmholtz, H. von. (1897/1903). ''Vorlesungen über Theorie der Wärme'', edited by F. Richarz, Press of Johann Ambrosius Barth, Leipzig, Section 46, pages 176-182, in German.</ref><ref>Planck, M. (1897/1903). ''Treatise on Thermodynamics'', translated by A. Ogg, Longmans, Green & Co., London, page 43. [http://www.onread.com/reader/145819]</ref><ref>Bridgman, P.W. (1943). ''The Nature of Thermodynamics'', Harvard University Press, Cambridge MA, page 23.</ref><ref>Guggenheim, E.A. (1949/1967). ''Thermodynamics. An Advanced Treatment for Chemists and Physicists'', 1st edition 1949, 5th edition 1967, North-Holland, Amsterdam, page 10.</ref><ref>Sommerfeld, A. (1952/1956). ''Thermodynamics and Statistical Mechanics'', Academic Press, New York, Section 4 A, pages 13-16.</ref><ref>{{cite book | author=Ilya Prigogine, I. & Defay, R., translated by D.H. Everett| title=Chemical Thermodynamics | year=1954 | publisher=Longmans, Green & Co., London, page 21.}}</ref><ref>Lewis, G.N., Randall, M. (1961). ''Thermodynamics'', second edition revised by K.S. Pitzer and L. Brewer, McGraw-Hill, New York, page 35.</ref><ref>Bailyn, M. (1994). ''A Survey of Thermodynamics'', American Institute of Physics Press, New York, ISBN 0-88318-797-3, page 79.</ref><ref>Kondepudi, D. (2008). ''Introduction to Modern Thermodynamics'', Wiley, Chichester, ISBN 978-0-470-01598-8, page 59.</ref>

Hukum termodinamik pertama mematuhi prinsip keabadian tenaga. Tenaga boleh berubah, contoh. bertukar dari satu bentuk kepadkepada abentukbentuk yang lain, tetapi tidak boleh dicipta atau dimusnahkan.