Figure 24 The Golden Gate Bridge is a landmark in San Francisco, California. Its cables, towers, and deck contain steel. The steel in the cables needs to resist forces that pull on the cables. The steel in the towers needs to resist the compression forces caused by the weight of the cables, the deck, and the vehicles that travel across the bridge.
Drawing Conclusions Would the steel used for the cables and the steel used for the towers have the same composition? Give a reason for your answer.
Other Alloys
Airplane parts are made of many different alloys that are suited to particular purposes. The body of a plane is large and needs to be made from a lightweight material. Pure aluminum is lighter than most metals, but it bends and dents too easily. If a small amount of copper or manganese is added to aluminum, the result is a stronger material that is still lighter than steel.
For certain aircraft parts, even lighter materials are needed. Alloys of aluminum and magnesium are used for these parts. Magnesium is much less dense than most metals used to build structures. However, pure magnesium is soft enough to cut with a knife, and it burns in air. An aluminum-magnesium alloy keeps the advantages of magnesium without the disadvantages.
Section 6.4 Assessment
Reviewing Concepts
What holds metal ions together in a metal lattice?- What characteristic of a metallic bond explains some of the properties of metals?
- How can scientists design alloys with specific properties?
Explain why the metallic bonds in some metals are stronger than the bonds in other metals.
Why are metals good conductors of electric current?
How does adding carbon to steel make the steel harder and stronger?
Critical Thinking
Predicting Which element has a higher melting point, potassium in Group 1A or calcium in Group 1B? Give a reason for your answer.
Applying Concepts Can two different elements form a metallic bond together?
Writing in Science
Compare-Contrast Paragraph Write a paragraph comparing the properties of ionic compounds and alloys. Relate their properties to the structure of their lattices.
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