14.1 Metals and alloys Flashcards
1
Q
General properties of metals
A
- good conductors of heat
- good conductors of electricity (free valence electron)
- ductile and malleable
- high density, melting pt, boiling pt
2
Q
Why pure metals are not widely used in industry
A
- Pure metals are soft
- pure: atoms packed regularly in layers and same size
- layers of atoms slide over each other easily when force applied - May react with water, air or wear away/corrode easily
3
Q
Alloys
A
mixture of metal with one or few other elements
4
Q
Why metals are used as alloys
A
- To make metals harder and stronger
- To improve the appearance of metals
- Lower melting points of metals
- Make metals more resistant to corrosion
5
Q
Alloys make metals harder and stronger
A
- Brass (alloy of copper and zinc)
- harder and stronger than pure copper/pure zinc
6
Q
Alloys improve appearance of metals
A
- Pewter (alloy of tin, antimony, copper)
- used to make ornaments, looks more beautiful than real tin
7
Q
Alloys lower melting pts of metals
A
- solder (alloy of tin and lead 0
- lower mp than most metals
- can be used to join electronic parts to circuit boards
8
Q
Alloys make metals more resistant to corrosion
A
- cupronickel (alloy of copper and nickel)
- used in coins, does not corrode easily
9
Q
Why are alloys stronger and harder than pure metals?
A
- alloy: atoms of diff elements/metals have diff sizes
- regular arrangement of atoms in pure metal disrupted
- cannot slide over each other easily when force applied
10
Q
Brass
A
- copper (70 percent), zinc (30 percent)
- does not corrode easily, attractive yellow/gold colour
- decorative ornaments, instruments
11
Q
Stainless steel
A
- iron (73%), chromium (18%), nickel (8%), carbon(1%)
- resistant to corrosion
- cutlery, medical instruments, pipes in chemical industries
12
Q
Solder
A
- tin(50%), lead (50%)
- low mp
- joining metals e.g. metal pipes
13
Q
Pewter
A
- tin (95%), antimony (3.5%, copper 1.5%)
- bright, shiny colour like silver
- decorative ornaments
