First law of thermodynamics / internal energy | Thermodynamics | Physics | Khan Academy
Why the open web links it
Explains the first law of thermodynamics and the concept of internal energy.
Linked by 4 independent sites, 2 of them widely read in the 2026-10 crawl of the open web, including oup.com, lumenlearning.com, jpsaos.com, projectideasblog.com.