Final answer:
A magnet loses its properties if it is hammered because the magnetic domains get disrupted.
Step-by-step explanation:
When a magnet is hammered, its properties are lost because the magnetic domains get disrupted. Each atom in a ferromagnetic material acts like a tiny bar magnet, and these small bar magnets are aligned in regions called domains. When the magnet is hammered, the atomic alignment within the domains gets disturbed, causing the magnet to lose its magnetic properties.