A candle's solid wax melts into liquid and then cools back into solid

Why

Deepika has spotted a real, dramatic change — solid turning to flowing liquid does look like a completely different substance appeared. What actually decides physical versus chemical isn't how DIFFERENT something looks, though, it's whether a genuinely NEW substance was formed that cannot easily be turned back. Melted wax is still wax, chemically identical to the solid it came from; nothing new was created, and cooling it simply returns the exact same solid wax, which is why you can melt and re-solidify the same candle wax again and again. A chemical change, by contrast, makes something the original substance simply is not — burnt paper cannot be turned back into paper, no matter how you cool or reshape the ash. Test: melt some wax, let it cool, then melt it again — it behaves identically each time, unlike, say, cooking an egg, which can never be uncooked back to raw. Her brother is right: melting only changes wax's STATE, not what it's made of, and being reversible back to the exact same substance is the sign of a physical change.