10. MetalsRevision from Year 10: Properties of Metals and Non-MetalsRead CC pp182-183

Use arrows to link the properties with the materials:

All of the above are physical properties apart from 4 (2 for metal and 2 for non-metals).

Highlight and label the chemical properties.Give equations below to show the chemical properties for metals:

Metals

Strong under tension and compression

Malleable

Low density

Have a dull appearance

Good conductors of electricity and heat

Can form negative ions when they react

Brittle

Shiny when polished

Sonorous

Usually form acidic oxides with oxygen

Poor conductors of electricity and heat

High density

Low melting and boiling points

Usually form basic oxides with oxygen

Usually form positive ions when they react

Ductile

Non-Metals

10. Metals

Reactivity of metals

We can deduce how reactive a metal is by observing how it reacts with other elements and compounds. We need to be able to use the reactions of a metal with water and dilute acid to determine its reactivity.

With water....

Write the reactions for the metals with an asterisk:

Metal: Reaction: Order of reactivity:

Products:

Potassium Violent reaction with cold water. Floats and catches fire.

1st Potassium hydroxide, KOH and hydrogen gas.

Sodium* Very vigorous reaction with cold water. Floats. Can be lit with a lighted splint.

2nd. Sodium hydroxide, NaOH and hydrogen gas.

Calcium Less vigorous with cold water. 3rd. Calcium hydroxide, Ca(OH)2 and hydrogen gas.

Magnesium Very slow with cold water, but vigorous with steam.

4th. Magnesium oxide, MgO and hydrogen gas.

Zinc* Quite slow with steam. 5th. Zinc oxide, ZnO and hydrogen gas.

Iron* Slow with steam. 6th. Iron oxide, Fe203 and hydrogen gas.

Copper No reaction with steam. 7th

10. Metals

With dilute hydrochloric acid...

NB. More reactive metals react with acid explosively.

Again, write the reactions for the indicated metals:

Notes:1. Aluminium is a reactive metal, but does not appear to be in its reaction with water and

dilutes acids. Why?

2. Sulphuric acid reacts in a similar way to hydrochloric acid, apart from with Calcium.

Why?

EXPT: Metals and Acids

Metal: Reaction with hydrochloric acid:

Order of reactivity:

Products:

Magnesium* Vigorously reacts with a stream of gas evolving.

1st Magnesium chloride, MgCl2 and hydrogen gas.

Zinc* Quite slow reaction with a steady stream of gas evolving.

2nd. Zinc chloride, ZnCl2 and hydrogen gas.

Iron Slow reaction with a gentle stream of gas evolving.

3rd. Iron chloride, FeCl2 and hydrogen gas.

Lead* Very slow and acid must be concentrated.

4th. Lead chloride, PbCl2 and hydrogen gas.

Copper No reaction. 5th

10. Metals

The reactivity series

Notes:

1. Metals above carbon in the list must be extracted using electrolysis.

2. The reactivity of a metal is a measure of how easily the metal loses electrons to form positive ions.

eg. Potassium loses its valence electron very easily and is very reactive.

Ionic EQN:

Copper resists losing its electrons and is relatively unreactive.

Ionic EQN:

3. A consequence of this is that reactive metals for very stable compounds - it is hard to make them form atoms again.

CC p184 Q1-4

10. Metals

Metals above carbon cannot be extracted by reduction of their oxides by carbon or carbon monoxide

Metals above hydrogen will react with acids to produce hydrogen gas

Thermal decomposition# of metal carbonates, hydroxides and nitrates

Compounds of Sodium and Potassium resist thermal decomposition as they are very stable.

The general rules are as follows:

Give an equation for the thermal decomposition of:

Zinc Carbonate

Calcium Hydroxide

Sodium Nitrate

Magnesium Nitrate

Demo: The above reactions

Do not decompose

Do decompose

Carbonates K, Na All other metals - to give the oxide and carbon dioxide*

Hydroxides K,Na All other metals - to give the oxide and water*

Nitrates Na and K give the nitrite and oxygen*

Other metals give the oxide, nitrogen dioxide and oxygen*

10. Metals

#Breaking down using heat

Competition for Oxygen

A more reactive metal will displace a less reactive metal from its oxide in an attempt to form a more stable oxide.

Eg1. Iron and Copper(II)Oxide

EQN:

Oxidation half equation:

Reduction half equation:

Eg2.Demo: Zinc and Copper(II)Oxide

EQN:

Half equations:

Oxidation:

Reduction:

Eg3: The Thermit Process

Aluminium with Iron(III)Oxide

EQN:

H is VERY negative

In all of the above reactions, heat is needed to start the reaction, then the large amount of heat that the reaction produces makes the reaction proceed rapidly.

The thermite process produces so much heat energy that molten iron is made, which can be used to repair railway tracks “in situ”.

Chemistry sometimes goes wrong...

http://www.youtube.com/watch?v=qqvQwfH_wGQDisplacement reactions in solution

10. Metals

Any more reactive metal will displace a less reactive metal from a solution of one of its salts.

Demo: Zinc and Copper Sulphate solution

EQN:

Ionic EQN:

Observations:

The reactive metal is acting as a REDUCING agent.

CC p187 Q1-6AV - ReactivityExpt: Competition between metals

Revision from Year 10: Simple Cells

Remember, placing 2 different metals in an electrolyte and making a circuit will cause an electric current to flow.

The greater the difference in reactivity of the 2 metals, the greater the voltage produced.

Note: the more reactive metal is called the negative pole, and the less reactive the positive pole.

Exam Questions: CC p192-193

10. Metals

10.3(a) Extraction of Metals

Read CC pp194-195

The extraction of a metal from its ore always involves the reduction of the metal.

General EQN:

The method of extraction depends on the reactivity of the metal. The more reactive the metal, the harder it is to extract.

Some specific

examples:

1. Copper

CHALCOPYRITE (mainly copper(II)sulphide) is roasted in air to give the metal and sulphur dioxide:

EQN:

10. Metals

2. Zinc

ZINC BLENDE (mainly zinc sulphide) is roasted in air to produce zinc oxide:

EQN:

This oxide is then reduced with carbon monoxide (the reducing agent):

EQN:

Iron is produced in a similar way (see below).DEMO: Lead from lead oxide

3. Aluminium (revision of Year 10)

Alumina is reduced using electrolysis, due to the fact that Aluminium is a more reactive metal:

EQN:

NB. The oxygen produced at the graphite ANODE reacts to give carbon dioxide and forces the periodic replacement of this electrode.

10. Metals

The Blast Furnace

The “charge” is the mixture of Haematite (Iron(III)Oxide), Limestone (Calcium Carbonate) and Coke (produced by heating coal in the absence of air).

You must learn the following “BIG 5 EQUATIONS”

1. Coke burns with oxygen in a very exothermic reaction (which heats the blast furnace):

EQN:

2. The limestone thermally decomposes:

EQN:

3. The carbon dioxide from reactions 1 and 2 reacts with more coke to produce the reducing agent (carbon monoxide):

EQN:

4. The Haematite is reduced:The molten iron collects at the bottom of the furnace.

EQN:

5. The calcium Oxide produced in reaction 2 reacts with impurities (mainly silicon(IV)oxide) to produce silicates.

EQN:

This material is commonly known as “slag” and is used for foundations for buildings and for making roads. The molten slag floats on the iron and is periodically removed.

10. Metals

Turning Cast Iron into Steel

The iron drained from the blast furnace contains a high percentage of carbon (4%) and some impurities. This is called “cast” iron or “pig” iron.

The high percentage of carbon makes it HARD and BRITTLE, and it is used for manhole covers, gates, fences, etc where strength is not important.

NB. Steel is an alloy of iron mixed with small amounts of carbon and other metals.

The process of making steel is:

1. Molten cast iron is poured into an oxygen furnace.2. Scrap iron is added.*3. Calcium oxide is added to remove impurities as slag:

EQN:

4. Oxygen is bubbled through the molten iron to remove the percentage of carbon (detectors control the carbon content).

EQN:

5. Other metals are added according to the alloy being made.

*This is how iron and steel are recycled. They can be separated from waste metals in scrapyards using an electromagnet and thrown into the oxygen furnace to be reused.

CC p199 Q1-510. Metals

Why make alloys?

Key concept: Uses depend on properties.

Adding a small amount of another metal (or carbon/silicon) to a pure metal can really changes its properties,

eg. malleability, ductility, strength, electrical conductivity, melting point, etc.

We can see why by considering the structure of an alloy.

Diagram:

Consider the alloys of iron:

Type of steel Iron alloyed with Properties Typical use

low carbon steel “Mild Steel”

about 0.25 percent carbon easily shaped car body panels

high carbon steel up to 2.5 percent carbon hard cutting tools

stainless steel chromium and nickel resistant to corrosion

cutlery, sinks, chemical plants,...

10. Metals

AluminiumCC pp202-203Fill in the following tables:

Uses and properties of pure aluminium (Year10)

Constitution, uses and properties of the Aluminium alloy “Duralumin” (7075TF)

CopperFill in the following tables:

Uses and properties of pure copper

Constitution, uses and properties of brass (one of copper’s alloys):

ZincUses and properties of pure zinc (as well as for making brass!):

Use Related properties

Made from... Use Related properties

Use Related properties

Made from... Use Related properties

Use Related properties

10. Metals

Task: Recycling metalsUsing the internet, investigate the advantages and disadvantages of recycling iron/steel and aluminium and construct a table listing them.

Exam Questions: CC pp208-209

Exam Questions

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