Key idea
Gibbs energy
ΔG = ΔH − TΔS
A negative ΔG indicates thermodynamic favourability for the specified change, but says nothing by itself about how fast it will happen.
Gibbs energy
The key idea
At constant temperature and pressure, Gibbs energy provides a criterion for the direction of spontaneous change in a closed system under the usual constraints.
Why it matters
A negative ΔG indicates thermodynamic favourability for the specified change, but says nothing by itself about how fast it will happen.
A picture to remember
Key idea
Gibbs energy
Guided example
Gibbs energy
A negative ΔG indicates thermodynamic favourability for the specified change, but says nothing by itself about how fast it will happen.
Put it into practice
Gibbs energy
Choose a concrete case linked to Gibbs energy. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.