The two ways to determine whether a bar of metal was magnetized or not are the following:
1. Rubbing the bar of metal with a strong magnet.
Find the north pole of the magnet then rub it on the middle part of the metal to the end. The act of rubbing the magnet several times across the metal helps the iron atoms (present in the metal) align in one direction. Then test the magnetism by tapping the metal against a pile of paperclips. If the paperclip stick, then the metal was magnetized.
2. Striking the bar of metal with a hammer.
Position the bar of metal facing north using a compass. Use a strong tape to secure it on the flat table. Strike the south part of the metal with a hammer several times. Striking the metal allows the iron atoms to align themselves in the direction of the Earth’s magnetic field. Then, test the magnetism of the metal.
Remember that a metal which contain the most iron will become more magnetic and an object is a magnet if it repels a known magnet.