Does making a chemical bond require energy?

1 Answer
May 5, 2016

The BREAKING of chemical bonds requires energy.


Bond formation is exothermic; bond breaking is endothermic.

When we combust a hydrocarbon, say methane, we have to break strong #C-H# and #O=O# bonds. But at the same time we form (stronger) #C=O# and #O-H# bonds:

#CH_4(g) + 2O_2(g) rarr CO_2(g) +2H_2O(l) + "energy"#

These energies can certainly be quantified, and the energy difference between bond breaking and bond making, the balance, can be both measured and predicted. For hydrocarbon combustion the energy balance is negative, and hydrocarbons combust exothermically.