Bond energy is the energy needed to break 1 mole of a bond in gaseous molecules.

• A. Bond energy is the energy needed to break 1 mole of a bond in gaseous molecules.
• B. Bond energy is the energy released when a bond forms.
• C. Bond energy is the energy required to change a solid to a liquid.
• D. Bond energy is the energy stored in chemical bonds of a solid.

Answer: (A)

Bond energy is about how strongly a bond holds a molecule together. Specifically, it is the energy needed to break a particular bond in a mole of molecules, usually measured for bonds in the gas phase. This is an endothermic process, so the value is positive, because you have to put energy in to overcome the bond’s strength. The gas-phase condition is important because it isolates the intrinsic bond strength without additional stabilization or lattice effects from solvents or solids.

The energy released when bonds form is the opposite concept—the bond formation energy (the negative of the bond dissociation energy). The other statements describe different processes: melting involves energy to change a solid to a liquid, and “energy stored in chemical bonds of a solid” isn’t a standard definition of bond energy.