Title: Summary Part I: The material world

Choose the correct statement.

- Today we use many materials that have been first discovered thousands of years ago, including metals (gold, copper and silver), glass and composited (such as wood or cement). (correct)
- Today we use many materials that have been first discovered thousands of years ago, including metals (such as steel, aluminum) and polymers.
- Modern society exclusively relies on materials that we have discovered and developed since the 18th century.

- The end of the 19th century brought about the age of silicon. Silicon is one of the key materials of our society because its tunable electrical conductivity is essential for the transistor – a microfabricated component that enabled modern information technology. (correct)
- The end of the 19th century brought about the age of silicon. Silicon is one of the key materials of our society because its high electrical conductivity is essential for the transistor – a microfabricated component that enabled modern information technology.
- The end of the 19th century brought about the age of silicon. Silicon is one of the key materials of our society due to its high structural strength.

- Silicon belongs to the materials class of semicondcutors. Another widely used semicondcutor is Germanium. (correct)
- Silicon belongs to the materials class of semicondcutors. Another widely used semicondcutor is Nylon.
- Silicon belongs to the materials class of metals. Another widely used metal is copper.

- Depending on the definition, there are different numbers of materials classes, ranging from three to six. (correct)
- There are six materials classes.
- There are three materials classes
- Depending on the definition, there are different numbers of materials classes. But there are at least ten.

- Structural engineering materials include the materials classes of metals, polymers, ceramics, glasses and composites. Of these, only metals, polymers and composites show ductility – this is why we find these materials in cars, airplanes and buildings.

Reminder: A high ductility is a desirable property that permits a material to undergo relatively severe impact loading without fracture – an essential behavior for many structural applications. The opposite of ductile is brittle. (correct)
- Structural engineering materials include the materials classes of metals, polymers, ceramics and glasses. Of these, only metals are ductile – this is why car frames and bridges and components for airplanes are all made of metal, for example steel and aluminium.

Reminder: A high ductility is a desirable property that permits a material to undergo relatively severe impact loading without fracture – an essential behavior for many structural applications. The opposite of ductile is brittle.
- Structural engineering materials include the materials classes of metals, polymers, ceramics and glasses. All of these are ductile – this is why they are all structural engineering materials.

Reminder: A high ductility is a desirable property that permits a material to undergo relatively severe impact loading without fracture – an essential behavior for many structural applications. The opposite of ductile is brittle.

- Metals, ceramics/glasses, and polymers can be classifed by their chemical bonding and atomic structure. Metals are associated with metallic bonding, ceramics/glasses with ionic bonding, and polymers with covalent bonding. This is why these classes are sometimes referred to as the basic classification of materials. (correct)
- Metals, ceramics/glasses, and polymers were discovered, developed and used much earlier in history than composites and semiconductors. This is why these classes are sometimes referred to as the basic classification of materials.