{"id":9950,"key":"First_law_of_thermodynamics","title":"First law of thermodynamics","latest":{"id":1207050,"timestamp":"2025-11-27T21:24:56Z"},"content_model":"wikitext","license":{"url":"https://www.appropedia.org/Appropedia:Copyrights","title":"CC-BY-SA-4.0"},"source":"The '''1st law of thermodyamics''' simply states that [[energy]] can be neither created nor destroyed (conservation of energy). Thus power generation processes and energy sources actually involve conversion of energy from one form to another, rather than creation of energy from nothing.<br><br>The first law can be modeled simply as: ∑W=∑Q\n\n== Implications ==\n\nThis has important implications in energy technologies. Burning a fuel creates energy by converting a high chemical energy substance (e.g. hydrocarbons) into low chemical energy substances (e.g. [[carbon dioxide]] and [[water]]). The energy changes form, to heat and mechanical energy, but is not created.\n\nIn contrast, a ''if a substance does not change form into a lower chemical energy state, then no energy can be extracted from it''.\n\nMost notably, [[Water as fuel|water cannot be used as fuel]] as the possible outputs are either:\n\n* Water at a similar temperature and in the same phase, i.e. having the same energy state - in which case we are looking at a perpetual motion machine,{{w|perpetual motion machine}} i.e. pseudoscience.\n* Water at a higher temperature or gaseous phase, in which case energy must have been ''used up'' to cause this change, rather than generated.\n* [[Hydrogen]] and [[oxygen]], which are at a higher energy state than water (demonstrated clearly by the fact that energy is released when hydrogen burns to form water). Again, energy must have been ''used up'' to cause this change, rather than generated.\n\n== Examples ==\n\n* Automobile Engine: Chemical to Kinetic\n* Heat/Furnace: Chemical to Heat\n* [[Hydroelectric]]: Gravitational to Electrical\n* Solar: Optical to Electrical\n\n== 1st Law Equation ==\n\n'''<big>ΔE= ΔQ-ΔW</big>'''\n\n* ΔE= change in internal energy\n* ΔQ= change in heat\n* ΔW= change in work\n\n== External links ==\n\n* [[Wikipedia:First law of thermodynamics]]\n\n{{Page data\n| license = CC-BY-SA-3.0\n}}\n\n[[Category:Energy]]\n[[Category:Physics]]\n[[Category:PH261]]"}