Home › CSEE (Form 4) › Chemistry › Physical and Chemical Change › What does the law of conservation of mass state …
What does the law of conservation of mass state about a chemical reaction?
AThe total mass always rises
BThe total mass always falls
CThe total mass stays the same
DThe number of molecules is fixed
Answer & Solution
Correct answer: C. The total mass stays the same
1. Atoms are neither created nor destroyed when a reaction takes place, they are rearranged.
2. The law of conservation of mass says the total mass of the substances taking part is conserved during the reaction.
3. So the mass of the reactants equals the mass of the products.
4. The number of molecules is a different matter and can change, so that option is the trap here.
_Source: Siyavula Physical Sciences Grade 10 (Everything Science, CC BY 4.0), Chapter 13: Physical and chemical change_