Learners discover that the enormous variety of objects in the human-made world can be sorted into just eight basic material categories. Students examine familiar objects and classify them by material, explore where each material comes from, and begin to notice that many objects are made of more than one material working together.

Key Ideas

• Noticing what things are made of, and asking why, is the first step to thinking like a scientist and an engineer.
• The material chosen for each part of an object depends on the properties that part needs — such as strength, flexibility, or heat resistance.
• Many objects are made from more than one material because different parts of the same object have different jobs to do.
• Some materials are natural — they come from the earth, from plants, or from animals. Others are synthetic, meaning humans invented them through chemistry.
• Almost every human-made object is built from one of eight basic material categories: metal, plastic, wood, glass, rubber, clay and stone, leather, or fibers.

Vocabulary

• Composite: An object or material made by combining two or more different materials together.
• Fiber: A long, thin strand that can be twisted or woven into fabric, rope, or carpet. Fibers can be natural such as cotton and wool, or synthetic such as polyester.
• Synthetic: Describes a material made by humans using chemistry, not found this way in nature. Examples include plastic and nylon.
• Natural: Describes a material that comes from the earth, from plants, or from animals — not manufactured by humans.
• Material: Any substance that objects are made from.

Discussion

• Why do you think different parts of the same object are made from different materials? Can you think of an example?
• What properties make a material useful for a particular job? For example, why might a cooking pan need a different material than a towel?
• Can you think of something made from several different materials? What job does each material do?
• What is the difference between a natural material and a synthetic material? Can you name an example of each?
• Pick an object near you. What materials is it made from, and why do you think the designer chose those materials?