I've seen a textbook use the two above expressions interchangeably. It could be argued that 'conservation
of matter' would be more appropriate since the discussion
below invokes the idea in a chemical reaction, atoms
are neither created or destroyed. More on this in
Nuclear Paradigm.
C6H14(l) + (19/2) O2(g) ->
6 CO2 + 7 H2O
reactant side
product side
6 carbons
6 carbons
14 hydrogens
14 hydrogens
19 oxygens
19 oxygems
For a balanced chemical equation, the total count for each atom should be the same on the product side as well as the reactant side.