During a chemical reaction, which of these quantities is not always conserved?

1. A reaction rearranges atoms into new groupings, it does not create or destroy them. 2. So the number of atoms of each kind is the same before and after. 3. Because the atoms are the same, the total mass is also the same. 4. The groupings themselves can change in number. 5. Two hydrogen peroxide molecules break down into two water molecules and one oxygen molecule. 6. That is two molecules turning into three, so the number of molecules is not conserved. 7. Assuming molecules must balance like atoms is the trap this item sets. _Source: Siyavula Physical Sciences Grade 10 (Everything Science, CC BY 4.0), Chapter 13: Physical and chemical change_