11/09/2015Metals. objectives What are metals? Names of common metals Uses and why Extraction methods...

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MetalsMetals

objectivesobjectives

• What are metals? Names of common metals

• Uses and why• Extraction methods• Problems

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MetalsMetals

• Most of the periodic table is made of metals, about 3 quarters

• Group 1 and group 2 reactive metals, transition metals and the poor metals

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Where are the transition Where are the transition metals?metals?

The transition metals are the block of elements located between group 2 and group 3 of the periodic table.

Ac Rf Db Sg Bh Hs Mt Ds Rg

La Hf Ta W Re Os Ir Pt Au Hg

Y Zr Nb Mo

Tc Ru Rh Pd Ag Cd

Sc Ti V Cr Mn

Fe Co Ni Cu Zn

?

Here, the word ‘transition’ is used to mean ‘in-between’.

group 2 group 3

The transition metals are known as ‘typical’ metals because of their physical properties. They are:

What are the properties of the transition What are the properties of the transition metals?metals?

lustrous (bright and shiny).

high density.

good conductors of heat and electricity.

high melting and boiling points (except mercury, which is liquid at room temperature).

hard and strong.

malleable (can be bent and pressed into different shapes) and ductile (can be drawn into wires).

Structure of a metalStructure of a metal19/04/23

structurestructure

• Free electrons allow metals to conduct heat and electricity

• Forms giant structures• In layers-so easy to slide over each

other. Bendy/malleable

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The Transition MetalsThe Transition Metals

1) This section includes metals like gold, mercury, iron, copper

Some facts…

2) They are all ______ and solid (except _________)

3) They are ____ reactive than the alkali metals

Words – hard, coloured, mercury, less, catalyst, insoluble

4) They can form __________ compounds, usually _______

5) They can be used as a ______ (a chemical that speeds up a reaction)

What are the uses of the transition What are the uses of the transition metals?metals?

Comparing properties of Comparing properties of different metalsdifferent metals

are more dense. This means that in a fixed volume of metal there are more atoms of a transition metal than there are of an alkali metal.

have higher melting and boiling points – except mercury.

are harder and stronger. They cannot be cut with a knife.

Compared to the alkali metals, the transition metals:

Comparing densities Comparing densities of metalsof metals

Comparing melting points Comparing melting points of metalsof metals

True or false?True or false?

How reactive are the How reactive are the transition metals?transition metals?

The transition metals are much less reactive than the alkali metals.

They tend to react relatively slowly, for example with air, water and acid.

Copper does not react with water whereas the alkali metals, such as sodium, react vigorously.

Copper does not burn in air whereas the alkali metals, such as sodium, burn vigorously.

How reactive are the How reactive are the transition metals?transition metals?

The general trend is for a decrease in reactivity from left to right across the periodic table. There are exceptions, such as zinc which is more reactive than expected.

Sc Ti V Cr Mn

Fe Co Ni Cu Zn

decrease in reactivity

Another exception is iron, which does react quite readily with air and water causing rust.

Zinc is more reactive than expected.

What is the chemical name of rust?

What happens to iron when What happens to iron when it rusts?it rusts?

Rusting is an oxidation reaction between iron, oxygen and water, which leads to the formation of hydrated iron (III) oxide - the chemical name for rust.

What are the word and chemical equations for the formation of rust?

water

oxygen

hydrated iron (III) oxide (rust)

iron

+ +

4Fe

(s)2H2O

(g)2Fe2O3.H2O+ 3O2

(g)+

Rusting is a type of corrosion.

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Rusting ExperimentRusting Experiment

RUST NO RUST – no water

NO RUST – no oxygen

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RustingRustingRust is formed when iron reacts with water AND _____.

It’s an example of an oxidation reaction which can be sped up using _____. There are several ways of dealing with rust:

1) Regular _______ or oiling

2) Galvanising – this is when iron objects are coated with ______

3) Making objects out of a non-rusting metal, such as ________ _______

4) Attaching zinc bars to ships – the water will react with the zinc before it reacts with the iron, because zinc is more ______

Words – stainless steel, reactive, painting, oxygen, salt, zinc

Transition metal Transition metal compoundscompounds

The number in brackets indicates how many electrons have been lost.

As most transition metals can form different ions, this means they can form multiple compounds.

Copper can form Cu+, which can make the red compound copper (I) oxide – Cu2O.

Copper can also form Cu2+, which can make the black compound copper (II) oxide – CuO.

Transition metal Transition metal compounds and colourcompounds and colour

Most transition metals form coloured compounds.

Copper (II) sulfate crystals (CuSO4.H2O) is blue – these can be turned white by heating the crystals to remove the water.

Iron (III) oxide (Fe2O3) is red/brown – when hydrated this is rust.

Iron (II) oxide (FeO2) is black.

For example:

Uses of coloured tm Uses of coloured tm compoundscompounds

The coloured compounds of transition metals can also be used in many ways, for example:

as coloured glazes on pottery.

to colour paints

to colour stained glass windows

The colour of many gemstones comes from the presence of transition metal compounds. For example, the gemstone jade contains iron.

How are transition metal ions How are transition metal ions identified?identified?

The presence of transition metal ions in a solution can be tested by adding sodium hydroxide solution.If transition metal ions are present, a metal hydroxide is formed. This is insoluble and so appears as a solid called a precipitate.

Cu2+ ions produce a blue precipitate of Cu(OH)2 .

Fe2+ ions produce a grey/green precipitate of Fe(OH)2 . Fe3+ ions produce an

orange/brown precipitate of Fe(OH)3

.

Different metal ions produce different coloured precipitates:

What is thermal What is thermal decomposition?decomposition?

Compounds of transition metals can be broken down into simpler substances by heating them.

For example, carbonates of transition metals are broken down into metal oxides and carbon dioxide when heated.

metal oxide

metal carbonate

+ carbon dioxidehea

t

How can the presence of carbon dioxide be tested?

This is called thermal decomposition.

The reactants and products are different colours.

The gas produced can be bubbled through limewater. If the gas is CO2, it will turn the limewater cloudy.

19/04/23Reactions of metals with Reactions of metals with oxygenoxygen

When a metal reacts with oxygen it will form a METAL OXIDE. This is what happens when a metal rusts. We can make this reaction happen quicker by burning the metal.

METAL + OXYGEN METAL OXIDE

Copy and complete the following reactions:

1) Magnesium + oxygen

2) Copper + oxygen

3) Calcium + oxygen

4) Iron + oxygen

Magnesium oxide

Copper oxide

Calcium oxide

Iron oxide

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Reactions of metals with waterReactions of metals with waterWhen a metal reacts with water hydrogen is always given off. The other product will be either a metal hydroxide or a metal oxide.


1) Sodium + water

2) Potassium + water

3) Calcium + water

4) Iron + steam

METAL + WATER METAL HYDROXIDE + HYDROGEN

METAL + WATER (vapour) METAL OXIDE + HYDROGEN

Sodium hydroxide + hydrogenPotassium hydroxide + hydrogenCalcium hydroxide + hydrogenIron oxide + hydrogen

19/04/23Reactions of metals with Reactions of metals with acidsacids

When a metal reacts with an acid it gives off hydrogen (which can be “popped” using a lit splint). The other product is a salt.


1) Calcium + hydrochloric acid

2) Zinc + hydrochloric acid

3) Iron + hydrochloric acid

4) Lithium + sulphuric acid

METAL + ACID SALT + HYDROGEN

e.g. magnesium + hydrochloric acid magnesium chloride + hydrogen

Calcium chloride + hydrogenZinc chloride + hydrogenIron chloride + hydrogenLithium sulphate + hydrogen

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Complete the following reactions:Complete the following reactions:

1) Lithium + water

2) Lithium + hydrochloric acid

3) Silver + oxygen

4) Magnesium + sulphuric acid

5) Potassium + oxygen

6) Aluminium + oxygen

7) Manganese + water

8) Sodium + sulphuric acid

9) Lithium + oxygen

10)Nickel + hydrochloric acid

Lithium hydroxide + hydrogen

Lithium chloride + hydrogen

Silver oxide

Magnesium sulphate + hydrogen

Potassium oxide

Aluminium oxide

Manganese oxide + hydrogen

Sodium sulphate + hydrogen

Lithium oxide

Nickel chloride + hydrogen

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The Reactivity SeriesThe Reactivity Series

The Reactivity Series lists metals in order of reactivity:

Potassium

Sodium

Calcium

Magnesium

Aluminium

Carbon

Zinc

Iron

Lead

Copper

Silver

Gold

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Displacement reactionsDisplacement reactions

SO4Cu

Copper sulphate

The magnesium DISPLACES the copper from copper sulphate

SO4Mg

Magnesium sulphate

Cu

Copper

A displacement reaction is one where a MORE REACTIVE metal will DISPLACE a LESS REACTIVE metal from a compound.

Magnesium + copper sulphate magnesium sulphate + copper

Mg

Magnesium

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Extracting MetalsExtracting Metals

A METAL ORE is a mineral or mixture of minerals from which it is “economically viable” to extract some metal.

To “extract” a metal from a metal oxide we need to REDUCE the oxygen. This is called a REDUCTION reaction. To put it simply:

Most ores contain METAL OXIDES (e.g. rust = iron oxide).

Some definitions:

Iron OxideIron ore

“Reduce” the oxygen to make

iron

19/04/23How do we do it?How do we do it?Potassium

Sodium

Calcium

Magnesium

Aluminium

Carbon

Zinc

Iron

Tin

Lead

Copper

Silver

Gold

Platinum

Metals ABOVE CARBON, because of their high reactivity, are extracted by ELECTROLYSIS

Metals BELOW CARBON are extracted by heating them with carbon in a BLAST FURNACE

These LOW REACTIVITY metals blatantly won’t need to be extracted because they are SO unreactive you’ll find them on their own, not in a metal oxide

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The Blast FurnaceThe Blast Furnace1) HAEMATITE (iron ore), limestone and coke (carbon) are fed in here

2) Hot air is blasted in here

3) The carbon reacts with oxygen from the air to form carbon dioxide.

4) The carbon dioxide reacts with more carbon to form carbon monoxide

6) Molten slag (waste) is tapped off here

5) Carbon monoxide reduces iron oxide to iron. The molten iron is tapped off here

Iron oxide + carbon monoxide iron + carbon dioxide

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ElectrolysisElectrolysis

Solid copper chloride ions

Solid copper chloride ions after being dissolved

Chloride ion

Copper ion

2

2

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ElectrolysisElectrolysis

++++

----

Positive electrode

Cu2+

Cu2+

Cu2+

Negative electrode

Cl-

Cl-

Cl-

Solution containing copper and

chloride ions

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ElectrolysisElectrolysisElectrolysis is used to extract a HIGHLY REACTIVE metal.

= chloride ion

= copper ion

When we electrolysed copper chloride the

negative chloride ions moved to the positive

electrode and the positive copper ions

moved to the negative electrode – OPPOSITES

ATTRACT!!!

19/04/23Redox reactionsRedox reactionsThese happen during electrolysis:

These two processes are called REDOX REACTIONS

OILRIG – Oxidation Is Loss of electrons

Reduction Is Gain of electrons

At the positive electrode the negative ions LOSE electrons to

become neutral – this is OXIDATION

At the negative electrode the positive ions GAIN electrons to

become neutral – this is REDUCTION

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Purifying Purifying AluminiuAluminiu

mm

Aluminium has to be extracted from its ore (called ________) by electrolysis. This is because aluminium is very ___________. The ore is mixed with cryolite to lower its ________ ________. The ore is then melted so that the ions can ______. The positively charged aluminium ions gather at the ___________ electrode. Oxygen forms at the positive electrode and causes it to wear away, which means that they have to be __________ frequently.

Words – melting point, replaced, negative, bauxite, reactive, move

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Purifying CopperPurifying Copper

++++

----

Solution containing copper ions

(copper sulphate)

Impure copper

Cu2+

Cu2+

Cu2+

Pure copper

At the positive electrode:

Cu(s) Cu2+(aq) + 2e-

At the negative electrode:

Cu2+(aq) + 2e- Cu(s)

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Using IronUsing IronIron produced by the blast furnace (“cast iron”) contains about 96% iron and 4% impurities. These impurities make it very brittle and easy to break.

Ironbridge, Shropshire – made out of cast iron and safe for horses and carts but not modern vehicles.

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Using IronUsing IronIn pure iron all impurities are removed. This makes the iron soft:

Adding 1% impurities makes the iron much stronger:

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Making steelMaking steel

Amount of carbon added (%)0.5% 1%

Strong

Weak

1.5%

Strength

Hardness

Steel with a low carbon content is easily shaped

Steel with a high carbon content is strong but brittle

Steel with chromium and nickel is called stainless steel

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AlloysAlloysSteel is an “alloy” – i.e. a mixture of metals. Here are other alloys:

Gold mixed with copper

Aluminium mixed with magnesium and copper

Aluminiun mixed with chromium

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Smart AlloysSmart AlloysA “smart alloy” is one that can “remember” its original state after being bent or stretched.

These glasses are made from a “smart” material – if they are bent they will return to their original shape

11/09/2015Metals. objectives What are metals? Names of common metals Uses and why Extraction methods...

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Transcript of 11/09/2015Metals. objectives What are metals? Names of common metals Uses and why Extraction methods...