Metals and Non-metals · Lesson 1 of 13
Physical Properties
“Metals show off with shine, strength, wires, sheets and the occasional ringing bell.”
• Explain the major physical properties used to describe metals. • Distinguish metallic lustre, malleability, ductility and sonority. • Explain why metals are widely used for wires, vessels and bells. • Compare good and comparatively poor conductors of heat among metals. • Connect the physical properties of metals with their everyday uses.
Metals are often recognised before any chemical reaction is performed. Their surfaces, the way they respond to force, the ease with which they can be shaped, and the way they conduct heat and electricity all provide useful clues. These properties also explain why different metals are chosen for different jobs.
Physical Properties
Metals
Metallic Lustre
Metallic Lustre is the characteristic shine shown by the clean surface of a metal.
A metal surface can become dull because of coatings formed during exposure. Rubbing a sample with sandpaper removes the outer coating and exposes a fresh surface, making metallic lustre easier to observe.
Hardness
Metals are generally hard, but hardness varies from metal to metal. Iron, copper, zinc and lead do not all resist cutting or hammering equally. Sodium is an important exception because it is soft enough to cut with a knife.
Malleability
Malleability is the ability of a metal to be beaten or pressed into thin sheets without breaking.
Gold and silver are highly malleable. Malleability allows metals to be shaped into sheets and vessels without the material shattering.
Ductility
Ductility is the ability of a metal to be drawn into thin wires.
Gold is highly ductile. Malleability and ductility are different: the first concerns sheets, while the second concerns wires. Together they explain why metals can be shaped for many uses.
Problem
A material can be hammered into a thin sheet and also drawn into a wire. Which properties are demonstrated?
- 1.Hammering into a sheet demonstrates malleability.
- 2.Drawing into a wire demonstrates ductility.
- 3.The two properties describe different kinds of shaping.
Conduction Of Heat
Metals are generally good conductors of heat and many have high melting points. Silver and copper are especially good conductors of heat. Lead and mercury are comparatively poor conductors among metals. Good heat conduction helps explain the use of metals such as aluminium and copper in cooking vessels.
Conduction Of Electricity
Metals generally conduct electricity. A conducting metal placed into a circuit can allow current to flow. Household wires therefore use metal conductors, but they are coated with PVC or rubber-like insulating materials to reduce the risk of accidental electric contact.
Sonority
A Sonorous material produces a ringing sound when struck.
Many metals produce a clear ringing sound when struck on a hard surface. This helps explain why bells are often made from metals.
| Property | Meaning | Connection To Use |
|---|---|---|
| Lustre | Shiny clean surface | Decorative objects |
| Malleability | Can be beaten into sheets | Metal sheets and vessels |
| Ductility | Can be drawn into wires | Electrical wires |
| Heat conduction | Transfers heat readily | Cooking vessels |
| Electrical conduction | Carries electric current | Electrical circuits |
| Sonority | Ringing sound when struck | Bells |
Quiz
What does malleability describe?
Which property describes drawing a metal into a wire?
Which metals are especially good conductors of heat?
Why are electrical wires coated with PVC or rubber-like material?
Why are bells commonly made of metals?
Practice Problems
- Explain how cleaning a metal surface can reveal metallic lustre.
- Differentiate between malleability and ductility using one example for each.
- Explain why copper or aluminium is suitable for cooking vessels.
- Explain why an electrical wire uses a metal core but an insulating outer coating.
- Gold can be beaten into sheets and drawn into wires. Name the two properties demonstrated.
- Describe how a hammer and a simple electrical circuit could test two physical properties of an unknown sample.
Key Takeaways
• Clean metal surfaces generally show metallic lustre. • Malleability is the ability to form sheets, while ductility is the ability to form wires. • Metals are generally good conductors of heat and electricity, although the degree varies. • Many metals are sonorous and produce a ringing sound when struck. • The physical properties of metals help explain their practical uses.
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Next · Lesson 2
Non-metals And Exceptions To Physical Properties