First Law (Chemistry Convention) (ΔU = q + w)
jee-mainjee-advancedneet-ug
ΔU = q + w
What each symbol means
| Symbol | What it stands for |
|---|---|
| q | Heat supplied to the system (J) |
| w | Work done on the system (J) |
| ΔU | Change in internal energy (J) |
When to use this
Closed system. NCERT chemistry: both q and w are positive when they increase the energy of the system. Expansion against external pressure: w = −P_extΔV (work on system negative).