Products have less energy that reactants.

630kJ + C₆H₆(1 ) → 3C₂H₂(g)

Energy flows out of the
system.

Reactants have less energy than products.

ΔH = + 45 kJ

ΔH = -2.4 x 10² J

2KC10₃→2KC1 + 3O₂ + 89.4 kJ