Which of these physical changes would require the liberation of energy, exothermic?
a. melting point
b. boiling point
c. condensation of steam to form liquid
d. sublimation from a solid to a gas
We’re being asked to determine which given reaction is exothermic.
• Exothermic reactions: lose energy and involve bonds forming; ΔH is negative
• Endothermic reactions: gain energy and involve bonds breaking; ΔH is positive