How come the bonds(grey sticks) were not included in the atomic mass?

Question

We did the conservation of mass acctivty.
My qeustions are that...
1. How come bodns were not included in the mass?
2. How come this reaction needed 2 oxygen molecules and water moleculres but only 1 of the others?
1). 1ch4+2o2
2).2o2

1. 1co2
2. 2 o2 molecules

Answer 1

Chemical bonds are actually pairs of electrons which are continuously being interchanged between the participating atoms. The mass of electrons is negligible compared to the nucleus.

Which reaction ?