THM-28

Gibbs energy

Isobaric-isothermal potential.

Reading speed

GoverningGibbs energy

Governing equation

G=H-TS

$T \in \left[200, 800\right]$

where

H: H (kJ)
T: T (K)
S: S (kJ/K)
G: Gibbs energy (kJ)

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

00:0 / 00:08

①

Governing law — red

G=H-TS

$T \in \left[200, 800\right]$

$T = 200$ $G = 120$

Along the curve

②

Domain of the variable — blue

T_{\min} = 200,\quad T_{\max} = 800

$T \in \left[200, 800\right]$

$T = 200$ $T = 200$

Along the curve

③

Response curve — green

G=H-TS

$T \in \left[200, 800\right]$

$T = 200$ $G = 120$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}G}{\mathrm{d}T}

$T \in \left[200, 800\right]$

$T = 203.8$ $G^{\prime} = -0.4$

Along the curve

Lecture brief

Historical brief

Carnot (1824), Clausius entropy, the first law and later van der Waals and Gibbs potentials turned heat into a state science. The sheets compute work, efficiency and vapour pressure. This sheet (THM-28 — Gibbs energy) is the form associated with Gibbs energy. Working symbols: $H$ , $T$ , $S$ $\rightarrow$ $G$ . Isobaric-isothermal potential. Pedagogical SI sheet with a live model and a swept parameter.

Purpose

Purpose: compute

G

from

H

T

S

in Thermodynamics via

G=H-TS

Isobaric-isothermal potential. Use it when a real thermodynamics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

H = 200.000\,\mathrm{kJ}

T = 298.000\,\mathrm{K}

S = 0.400\,\mathrm{kJ/K}

, the governing relation

G=H-TS

yields

G = 80.800\,\mathrm{kJ}

. One governing identity, SI units, a single sweep on the sheet. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

H H200 kJT T298 KS S0.4 kJ/K

Outputs

Gibbs energy G80.800 kJ

Reading speed

Watch on YouTube

Free library

Full library

Free PDF / open book

YouTube channels

00:0 / 00:08

Narration of this film

One governing identity, SI units, a single sweep on the sheet.

Isobaric-isothermal potential. Pedagogical SI sheet with a live model and a swept parameter.

Reading speed

Watch on YouTube