During a chemical reaction, the statement that is most likely to occur is "Mass is conserved."
In a chemical reaction, the total mass of the reactants is equal to the total mass of the products, in accordance with the law of conservation of mass. The original substance might change its properties and form new substances, but the total number of atoms remains the same; they are merely rearranged. Thus, new atoms are not created, and atoms of the original substance are not lost in the process.