1411739656 2014 Chemistry Notes Essay

Submitted By madisonjun
Words: 2494
Pages: 10

Preliminary Chemistry Module 2: Metals

Metals have been extracted and used for many thousands of years

1.1 Outline and examine some uses of different metals through history, including contemporary uses, as uncombined metals or as alloys:
Age
Dates
Name of Metal
Uses of metal
Properties of Metal
Copper Age
5000-3000BC
Copper
Ornaments
Tools
Weapons
Cooking implements
Electrical Wires
Water pipes
Easy to work
Good conductor of electricity
Nice and shiny
Corrosion resistant
Bronze Age
3000-1000BC
Bronze – an alloy of copper
Cutting tools shields & armour statues church bells bearings Lower melting point yet harder than Copper quite malleable and ductile
Iron Age
From 1000BC
Iron
Weapons and tools
Magnetic application
Converted into carbon steels (iron-carbon alloys)  used in building construction framework cars machinery household appliances
Very malleable and ductile reasonably hard abundant in the crust quite heavy very magnetic
Modern Era
Present day
Aluminium
Titanium
Gold
- Aluminium: saucepans, drink cans, cooking foil
- Titanium: alloys used in spacecrafts and aircrafts
- Gold: jewellery, electrical connections
- Aluminium:
Low density high thermal conductivity very high corrosion resistance very malleable and ductile
- Titanium:
Quite strong
Quite malleable/ductile
- Gold:
Very malleable/ductile
Good electrical conductor
Shiny and lustrous
Corrosion resistant

1.2 Describe the use of common alloys including steel, brass and solder and explain how these relate to their properties:

Alloy
Composition
Properties
Use(s)
Steel
99.8% Fe, 0.2% C
Hard but easily worked
Nails
Cables & chains
Brass
65% Cu, 35% Zn & small amounts of other elements eg. Pb, Sn & Al lustrous gold appearance, hard but easily machined, polishes well
Plumbing fittings, musical instruments, decorations.
Solder
33% Sn, 67% Pb
Low melting point
Adheres firmly to other metals when molten
Joining metals together (plumbing and electrical)
Stainless steel
74% Fe, 18% Cr, 8% Ni
Resists corrosion
Sinks, cutlery
1.3 Explain why energy input is necessary to extract a metal from its ore:

Energy input is necessary to extract a metal from its ore because many metals are bonded very strongly with their ores which requires energy to break the chemical bonds (the more reactive the metal, the more energy input required)
Energy has to be supplied: to mine the ore, to purify or concentrate the ore, to extract the metal, to purify the metal or form an alloy

1.4 Identify why there are more metals available for people to use now than there were 200 years ago:

Only ten metals were in use before the 19th century because heat energy alone was not sufficient to decompose their compounds
The invention of electrolysis in the 19th century allowed for metals such as calcium, potassium and sodium to be discovered
Today metals have become readily available due to ongoing improvements in mining, smelting techniques and transportation due to the technological boom

Metals differ in their reactivity with other chemicals and this influences their uses

2.1 Describe observable changes when metals react with dilute acid, water and oxygen:

Water: K, Na, Ca – react with cold water to form hydroxide ions and hydrogen gas
Mg – reacts with hot water to form hydroxide ions and hydrogen gas
Al, Zn, Fe – react with steam at red heat to form oxide ions and hydrogen gas
Cold water
K
Ease of oxidation of metal decreases down the column.
Ease of reduction of metal ions increases down the column.

Na

Li

Ba

Ca

Steam & oxygen
Mg

Al

Zn

Fe

Dilute acids
Sn

Pb

Oxygen
Cu

Ag

Pt

Au

Sn, Pb, Cu, Hg, Ag, Au – No reaction

Oxygen: K, Na, Ca – burn rapidly to form oxides
Mg, Al, Zn, Fe – burn rapidly (if powdered or as fine fibres) to form oxides
Sn, Pb, Cu, Hg – become coated with oxide layers during heating
Ag, Au – No reaction

Dilute Acid: K, Na – foam rapidly producing metal salt and hydrogen gas
Ca, Mg – bubble rapidly…