1. PATTERNS OF REACTIVITY
In This Section We Will Be Studying The Following Topics:
Metals in air.
Metals in water.
Metals in acids.
Metal displacement.
Reactivity series.

2. METALS IN AIR
Metals react with acids to produce a salt, and hydrogen gas
Some metals react more vigorously than others.
Do they react with air, which contains oxygen and water vapour, at different speeds as well?
When a shiny new piece of metal is exposed to moist air it reacts with oxygen in the air losing its shine. It is said to become tarnished.
Exposure to moist air.
Not only can metals become tarnished but they can change colour - either change is evidence of a chemical reaction.

3. METALS IN AIR
Pieces of different metals were exposed to air at room temperature. The following graph was drawn:
Other metals included zinc, calcium, iron, magnesium, copper and silver but not gold.
Looking at the graph we can see that potassium, sodium and lithium, in that order, are the most reactive in oxygen.

4. METALS IN AIR
Gold is a special case and not just because it is a ‘precious’ metal.
Besides being a rare and attractive metal, what else is special about gold that makes it a good metal for jewellery?
It does not tarnish.
We can now start to create a table listing the metals from most to least reactive.
Most Reactive.
Reaction With Oxygen
Least Reactive.
Potassium.
Sodium.
Lithium.
Calcium, iron, magnesium, zinc, silver and copper.
Gold.

5. METALS IN WATER
To see how metals react with cold water, 1g of each metal was placed in a trough of water (behind a safety screen). The results were recorded in a table.
Did not appear to react
Magnesium
495 sec
Calcium
295 sec
Lithium
25 sec
Sodium
15 sec
Potassium
Time to reach end of reaction
Metal
This investigation has given another metal - calcium - to add to the table.

6. Calcium, iron, magnesium, zinc, silver, copper
METALS IN WATER
Most Reactive
Reaction With Oxygen
Least Reactive
Potassium
Sodium
Lithium
Calcium, iron, magnesium, zinc, silver, copper
Gold
Most Reactive
Reaction
With
Water
Least Reactive
Potassium
Sodium
Lithium
Calcium
Other Metals
Gold
When the gas is collected from the reaction in a test tube and is lit by a splint it makes a popping sound. What gas is it?
I know it’s..
hydrogen

7. The General Equation Is:
METALS IN WATER
If the water in the trough is tested after reacting with a metal it would be found to be alkaline.
What colour would Universal Indicator change to?
It would change to blue.
When a metal reacts with water, besides producing hydrogen it produces a metal hydroxide. If this dissolves in water it will make an alkaline solution.
The General Equation Is:
metal + water → metal hydroxide + hydrogen
So for calcium: calcium + water → calcium hydroxide + hydrogen

8. Vigorous reaction and hot.
METALS IN ACIDS
Metals react with acids at different speeds, the same way that they do with oxygen and water.
It would be too dangerous to test potassium, sodium or lithium with acids in a classroom because of their vigorous reactions.
Calcium is the first metal we can test with acids. However, we have seen that it reacts with water and have already placed it in the table.
The reactivity of the other metals can be judged by how much heat is generated and by the rate at which hydrogen is produced.
Magnesium
Iron
Zinc
Vigorous reaction and hot.
Quick reaction and warm.
Slower reaction and cool.

9. What is the one common metal not mentioned so far?
METALS IN WATER
The results of the acid investigation give us magnesium, zinc and iron in order of reactivity.
One of the reasons for not testing calcium in acid is that it behaves in an unexpected way, because it does not react as vigorously as its place in the table would suggest.
When calcium reacts with sulphuric acid, calcium sulphate is one of the products. This builds up a layer on the surface of the calcium, preventing acid reaching any remaining calcium; so the reaction stops very quickly.
It reacts very quickly with hydrochloric acid, though
Calcium atoms
Calcium Sulphate layer
Acid cannot reach the calcium
What is the one common metal not mentioned so far?
Aluminium.
Aluminium comes between magnesium and zinc in the table, but it is hard to test. Aluminium, when exposed to oxygen, quickly forms a layer of aluminium oxide on its surface. Aluminium oxide is very un-reactive to many chemicals including water and acids.
Aluminium atoms
Aluminium Oxide layer
Chemicals do not react

10. METAL DISPLACEMENT The Table So Far: The zinc has displaced the iron.
Most Reactive
Least Reactive K Na Li Ca Mg Al Zn Fe Cu Ag Au
There is only Copper and Silver to put in order for our table to be complete.
In chemistry, displacement happens when one chemical has moved or pushed out another chemical from one of its compounds.
Zinc + Iron Sulphate → Zinc Sulphate + Iron
The zinc has displaced the iron.
Magnesium + Zinc Nitrate → Magnesium Nitrate + Zinc
The magnesium has displaced the zinc.
What has been displaced here?

11. METAL DISPLACEMENT
Hey Professor, I’ve noticed something about those displacement reactions.
What’s that Moley?
Well observed Moley! We say that the higher metal is more reactive than the lower metal.
The displaced metal is lower down the table than the metal that displaces it.
We can use a displacement reaction to help us put silver and copper in the correct order.
If copper is placed in a silver nitrate solution, the solution slowly turns green and a layer of silver is deposited.
Copper has displaced the silver from the nitrate and so copper is higher up the table and therefore more reactive than silver.

12. REACTIVITY SERIES Potassium Sodium The final table is: Lithium Calcium
Most Reactive.
The final table is:
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Zinc
Iron
Copper
Silver
Gold
This table, called the reactivity series, shows how the more common metals react. So it is possible to predict the likely outcome of chemical reactions involving the metals.
Least Reactive.

13. Which metals do you think these are? Why?
REACTIVITY SERIES
By looking at the reactivity series it is possible to say which metals are more likely to be found in their natural form.
Silver and gold because these are the least reactive. They are found as lumps of gold or silver, not as compounds called ores.
Which metals do you think these are? Why?
Metals such as copper and iron have been know to man for several thousand years because they are easily extracted from their ores.
Aluminium
Zinc
Carbon
Iron
Copper
Silver
Gold
Metals at the top of the reactivity series have only been discovered in the last few hundred years because they are strongly joined to other elements.
If we introduce carbon, a non-metal, into the reactivity series, we can see the metals that are most easily extracted.

14. Iron Oxide + Carbon → Iron + Carbon Dioxide
REACTIVITY SERIES
Iron can be extracted from its ores, usually an oxide, by heating the ore with carbon.
Iron Oxide + Carbon → Iron + Carbon Dioxide
Heat
Copper can be extracted from its oxide in the same way.
Metals above carbon, such as aluminium or sodium, are extracted by passing large electric currents through their molten ore. This is called electrolysis.
This is expensive and uses a lot of electricity.

15. REACTIVITY SERIES
In the thermite reaction, iron is produced by reacting iron oxide with aluminium. Why does this happen?
Aluminium displaces the iron because it is the more reactive of the two metals.
Why are gold and silver used for jewellery?
They do not react with other chemicals and so keep their shine.
Copper is usually used for water pipes. Why not iron or magnesium?
They are both more reactive, especially magnesium and would react with water and the chemicals carried by the water.
Salt, sodium chloride, is very common but why is it so hard to extract the sodium?
Sodium is very reactive and bonds tightly with other elements. It takes a lot of energy to break the bonds.

16. REACTIVITY SERIES What Have We Learned?
Metals react with acids (apart from gold) to produce a salt and hydrogen. Some metals react more vigorously than others.
When a metal reacts with water, hydrogen and a metal hydroxide are produced. If the metal hydroxide is dissolved in water it will make an alkaline solution.
The reactivity of aluminium is hard to test. Aluminium, when exposed to oxygen, quickly forms a layer of aluminium oxide on its surface. Aluminium oxide is very un-reactive to many chemicals including water and acids.
In a reaction a more reactive metal displaces a less reactive metal.
By looking at the reactivity series it is possible to say which metals are more likely to be found in their natural form. More reactive metals are harder to extract from compounds/ores.