INTERNAL ENERGY Quick Facts Concept Key Point
Internal Energy (E) Total energy (kinetic + potential) of all particles in a system
Kinetic Energy Due to translational, rotational, vibrational motion
Potential Energy Due to bonds, van der Waals forces, attractions
ΔE (Change) State function ✅ (depends only on initial & final states)
Absolute Value Cannot be measured – only ΔE can be measured
🔥 HEAT & WORK – The Two Energy Transfer Modes
HEAT (q) Property Detail
Symbol q State Function?
NO ❌ (path-dependent)
q = +ve Heat ABSORBED by system (endothermic) q = -ve Heat RELEASED by system (exothermic)
WORK (w) Property Detail Common Type
Pressure-Volume Work (P-V work)
Formula w = -PΔV State Function?
NO ❌ (path-dependent) w = +ve Work DONE ON the system w = -ve Work DONE BY the system
| State Functions ✅ | Path Functions ❌ |
|---|---|
| Internal Energy (E) | Heat (q) |
| Pressure (P) | Work (w) |
| Volume (V) | |
| Temperature (T) |
Memory Trick: “E, P, V, T are STATE-ly affairs”
**q and w are PATH-etic (depend on path!)”