Just about every solid material possesses some degree of elasticity, as do most liquids. The key to determining whether a substance is elastic is to apply a force to it; with sufficient force, the substance should change its size, shape, or volume. If, when the force is removed, the sample returns to its original state, then it is elastic; if the substance returns only partially (or not at all) to its original state, it is called inelastic. If too much force is applied, the material is in danger of reaching its elastic limit --that is, the point at which the material is bent beyond its ability to return to its original shape. Once the elastic limit is passed, the material will experience permanent reshaping, called plastic deformation, and will no longer act as an elastic substance. This is easily evidenced by hanging a weight from a spring: if...