Misconceptions about Bonds

The AP chem teacher was telling me the other day that one of the most persistent misconceptions in chemistry is that breaking molecular bonds can release energy. Of course all bonds require energy to be broken (think of two items glued together - no matter how they are glued, it takes energy to separate them!)

The reasons for this misconception is because most people don't understand energy and its relative nature. The misconception persists because people know:

1. That chemical reactions can release energy (e.g. exothermic reactions)
2. That energy can be released by 'splitting the atom' (e.g. the fission of U-235)
3. ATP is used for energy production in cells (biologists sometimes will incorrectly say "energy is released when ATP loses a phosphate group")

What these have in common is that they have a nice image: picture breaking open something and watching the goo come out (the goo seems like energy). This is completely wrong (energy is a complete abstraction - it is not something physical like goo) but I think this is what people picture and leads them to misconceptions about energy and bonds

1. Chemical reactions can absorb energy (e.g. endothermic reactions)
2. Nuclear reactions can absorb energy (e.g. the fission of most elements lighter than iron)
3. It takes energy to rip the phosphate group off of ATP

So what really counts is not the breaking or splitting, but the relative bond energies before and after.

1. WRONG: Chemical energy was stored in the bond and then released

CORRECTED: Energy was required to break the bond, but more was released when the new one was formed.

2. WRONG: Nuclear energy came from the breaking of the strong nuclear bonds

CORRECTED: If the nuclei in the end have less mass than in the begining then energy was released

3. WRONG: ATP --> ADP + energy

CORRECTED: The phosphate group falls into a stronger bond with the surrounding water than it had with ADP and therefore releases energy overall ( as in #1 above)

A graphic indicating that ALL bonds are negative energy situations!