NSES Content Standard E   Science and Technology: Abilities to distinguish between natural objects and objects made by humans  Grades K-4, page 138  Some objects occur in nature; others have been designed and made by people to solve human problems and enhance the quality of life.

 
Benchmark 8B The Designed World: Materials and Manufacturing
Grades 3-5, page 188
Naturally occurring materials such as wood, clay, cotton, and animal skins may be processed or combined with other materials to change their properties.

Benchmark 8B The Designed World: Materials and Manufacturing
Grades 3-5, page 188
Through science and technology, a wide variety of materials that do not appear in nature at all have become available, ranging from steel to nylon to liquid crystals.