Chemical changes involve forming new substances via bond breaking/forming

Steps:

• Recall chemical change definition: rearrangement of atoms into new substances through breaking/forming intramolecular bonds.
• Examine option A: breaking covalent bonds in methane (CH₄) implies reaction like combustion, producing new molecules (e.g., CO₂, H₂O).
• Check options B–D: assess if they involve only physical separations without new substances.
• Identify A as the only process requiring chemical bond breakage for transformation.

Why A is correct:

• Breaking covalent bonds in molecules, per chemical reaction definition, forms new substances, unlike reversible physical processes.

Why the others are wrong:

• B: Breaking intermolecular attractions in water is a physical change, like evaporation, without altering molecular structure.
• C: Breaking ionic bonds in NaCl lattice is a physical change, such as dissolving, yielding separated ions but no new compounds.
• D: Manufacturing brass alloys copper and zinc physically, creating a homogeneous mixture without bond formation or new substances.

Final answer: A