$\Delta G$ is equal to $\Delta G^{\circ}$ when the system is at the standard state.

$\Delta G^{\circ}$ is zero when the system is at equilibrium.

$\Delta G$ measures activation energy of a reaction.

When $\Delta G$ is positive, the reaction should proceed forward to form more product.

$\mathrm{NaCl}(\mathrm{s}) \longrightarrow \mathrm{Na}(\mathrm{g})+\mathrm{Cl}(\mathrm{g})$

$\mathrm{NaCl}(\mathrm{s}) \longrightarrow \mathrm{Na}^{+}(\mathrm{g})+\mathrm{Cl}^{-}(\mathrm{g})$

$\mathrm{Na}(g)+\mathrm{Cl}(g) \longrightarrow \mathrm{NaCl}(s)$

$\mathrm{Na}^{+}(g)+\mathrm{Cl}^{-}(g) \longrightarrow \mathrm{NaCl}(\mathrm{s})$

$\mathrm{H}_2(\mathrm{~g}) \longrightarrow 2 \mathrm{H}(\mathrm{g})$

Liquid water crystallises to ice

Temperature of ice is raised from 10 K to 115 K

$2 \mathrm{NaHCO}_3$ (s) $\longrightarrow \mathrm{Na}_2 \mathrm{CO}_3$ (s) $+\mathrm{CO}_2$ (g) $+\mathrm{H}_2 \mathrm{O}$ (s)

The energy of the isolated system plus the energy of the surrounding is constant.

The energy of the isolated system minus the energy of the surrounding is constant.

The energy of an isolated system is constant.

The energy of an isolated system varies.