• # Crosscutting Concepts

### 6. Structure and Function

Below is the progression of the Crosscutting Concept of Structure and Function, followed by Performance Expectations that make use of this Crosscutting Concept.

#### 6. Structure and Function

The way an object is shaped or structured determines many of its properties and functions.

#### Primary School (K-2)

• The shape and stability of structures of natural and designed objects are related to their function(s).

#### Elementary School (3-5)

• Different materials have different substructures, which can sometimes be observed.
• Substructures have shapes and parts that serve functions.

#### Middle School (6-8)

• Structures can be designed to serve particular functions by taking into account properties of different materials, and how materials can be shaped and used.
• Complex and microscopic structures and systems can be visualized, modeled, and used to describe how their function depends on the shapes, composition, and relationships among its parts, therefore complex natural structures/systems can be analyzed to determine how they function.

#### High School (9-12)

• Investigating or designing new systems or structures requires a detailed examination of the properties of different materials, the structures of different components, and connections of components to reveal its function and/or solve a problem.
• The functions and properties of natural and designed objects and systems can be inferred from their overall structure, the way their components are shaped and used, and the molecular substructures of its various materials.

This is a table of the Crosscutting Concept of Structure and Function. If coming from a Standard the specific bullet point used is highlighted and additional performance Expectations that make use of the Crosscutting Concept can be found below the table. To see all Crosscutting Concepts, click on the title "Crosscutting Concepts."

## Structure and Function

Structure and Function are complementary properties. "The shape and stability of structures of natural and designed objects are related to their function(s). The functioning of natural and built systems alike depends on the shapes and relationships of certain key parts as well as on the properties of the materials from which they are made. A sense of scale is necessary in order to know what properties and what aspects of shape or material are relevant at a particular magnitude or in investigating particular phenomenaâ€”that is, the selection of an appropriate scale depends on the question being asked. For example, the substructures of molecules are not particularly important in understanding the phenomenon of pressure, but they are relevant to understanding why the ratio between temperature and pressure at constant volume is different for different substances.

"Similarly, understanding how a bicycle works is best addressed by examining the structures and their functions at the scale of, say, the frame, wheels, and pedals. However, building a lighter bicycle may require knowledge of the properties (such as rigidity and hardness) of the materials needed for specific parts of the bicycle. In that way, the builder can seek less dense materials with appropriate properties; this pursuit may lead in turn to an examination of the atomic-scale structure of candidate materials. As a result, new parts with the desired properties, possibly made of new materials, can be designed and fabricated." (p. 96-97)