TeXes Science Practice Test 2026 – The Definitive All-in-One Guide to Exam Success!

The First Law of Thermodynamics is a fundamental principle that states that the internal energy change of a system (ΔU) is equal to the heat added to the system (ΔQ) minus the work done by the system (ΔW). This relationship is encapsulated in the equation ΔU = ΔQ - ΔW.

In this context, ΔQ represents the energy transferred to the system through heat, which increases the internal energy. Conversely, ΔW refers to the work done by the system on its surroundings, which would decrease the internal energy. Therefore, the accurate formulation considers heat energy added positively to the system while work done by the system is subtracted, indicating that the system is losing energy.

This foundational concept helps explain how energy is conserved within a closed system and allows for the analysis of various thermodynamic processes. Understanding this law and its implications is crucial for fields such as physics, chemistry, and engineering.