An object is a thing with a shape, such as a spoon. A material is what it is made of, such as steel, wood or plastic. The same object can be made from different materials: a spoon can be steel, wood, plastic or silver, and each one feels and behaves differently.

Engineers describe a material by its properties. A property is something you can observe or measure, and it does not depend on how big the piece is. Here are the everyday ones:

• Hard or soft: does it resist being scratched or dented? A steel knife scratches a copper coin, but not the other way round.
• Stiff or flexible: does it spring back when you bend it only a little, or does it bend easily? A steel ruler is stiff, a rubber band is flexible.
• Brittle or tough: does it snap suddenly, or does it take a lot of abuse first? Glass is brittle; a rubber ball is tough.
• Light or heavy: how much mass is packed into each cubic metre? That is the density.
• Conductor or insulator: does heat or electricity pass through easily?