First Law of Thermodynamics — Predicted 2026

AI-Predicted Question Angles for UPSC 2026

Based on trend analysis, current affairs, and recurring themes in First Law of Thermodynamics.

Combined Process Analysis

high

NEET often tests the ability to apply concepts across multiple steps. A question might describe a two-step process (e.g., isothermal expansion followed by adiabatic compression) and ask for the overall $Delta U$, $q$, or $w$. This requires applying the First Law and specific formulas for each step, and then summing the path functions ($q, w$) while noting that $Delta U$ is a state function. This tests a deeper understanding of process characteristics and the nature of state/path functions.

Application to Chemical Reactions (Thermochemistry)

high

The First Law is the foundation of thermochemistry. Questions might involve calculating $Delta U$ from $Delta H$ (or vice-versa) for a chemical reaction using the relation $Delta H = Delta U + Delta n_g RT$. This requires identifying the change in gaseous moles ($Delta n_g$) and correctly applying the gas constant $R$ and temperature $T$. This angle directly links the First Law to practical chemical scenarios, which is a favorite for NEET.

Graphical Interpretation of Work and Heat

medium

While less common, questions involving P-V diagrams can appear. Students might be asked to identify the work done (area under the P-V curve) for different paths or to compare work done in reversible vs. irreversible processes. Understanding that work is a path function and how it's represented graphically is a higher-order skill that can differentiate top performers. This could involve identifying processes from the graph or calculating work from given points.

Heat Capacity and Internal Energy/Enthalpy Changes

medium

Questions might involve calculating $Delta U$ or $Delta H$ using heat capacities ($C_v$ or $C_p$) and temperature changes. For example, $Delta U = nC_vDelta T$ and $Delta H = nC_pDelta T$. This could be combined with Mayer's relation ($C_p - C_v = R$) or the adiabatic index ($gamma = C_p/C_v$) for ideal gases. Such questions test the interrelationship between different thermodynamic quantities.