We sometimes call valuable metals, such as platinum and gold, precious metals. Platinum is the most valuable metal in the world. It is called a catalyst because it produces a chemical reaction in other substances without itself changing. Platinum is more expensive than gold and is used in many industries. Another metal, iridium, is often used as a hardening agent for platinum.
Gold is the third most valuable metal after platinum and iridium. It can be rolled and stretched more than any other metal. Gold is used to make jewelry and some electronic equipment. Copper is often added to gold to make it harder.
Another precious metal is silver, which loses its shine, or luster, when exposed to the air. Silver must be polished to remove any stains. The photographic film in your camera contains silver, and many ornaments and pieces of jewelry are made of silver.
Another precious metal is silver, which loses its shine, or luster, when exposed to the air. Silver must be polished to remove any stains. The photographic film in your camera contains silver, and many ornaments and pieces of jewelry are made of silver.
Social Plugin