Metal reactions

Question 1

Reactions of Reactive Metals with Water

Potassium, sodium and lithium all react quickly with cold water to produce a metal hydroxide and hydrogen gas.

Answer 1

Potassium

Potassium is the most reactive so reacts very quickly.
The hydrogen produced ignites instantly and the metal also sets alight, sparking and burning with a lilac flame.

Sodium

Sodium fizzes rapidly and melts to form a ball that moves around on the water surface.

Lithium

Lithium fizzes steadily and floats, becoming smaller until it eventually disappears.

Question 2

Reactions of Metals with Dilute Acids

Most metals react with dilute acids to give a salt (e.g. copper chloride) and hydrogen gas.

Answer 2

Metals that do react with dilute acids

Metals don’t have to be that reactive to react with dilute acids.
The metals that react with dilute acids but not cold water are magnesium, aluminium, zinc, iron and lead (iron and lead react slowly).

Question 3

Alternative Methods of Extracting Copper

Phytomining is a technique that allows us to extract copper from contaminated land. A technique called bioleaching has improved our ability to extract copper from low-grade ores

Answer 3

Bioleaching

Bacteria are added in with low-grade ores.
The bacteria break down the ores to create a solution rich in copper compounds known as a leachate solution. We can easily extract copper from leachate solution.
Similarly to phytomining, bioleaching is a much slower process than traditional mining.

Phytomining

Plants growing on contaminated land absorb copper ions as they grow.
These plants are harvested and burned, producing ash that contains high concentrations of copper compounds.
A disadvantage of phytomining is that the process takes a lot longer than the classic methods.

Question 4

Explain what you understand by the term alloy.

Answer 4

• a mixture of (1)

* metals (1)

Question 5

Aluminium is extracted by the electrolysis of a molten mixture of its ore (bauxite)
and cryolite.
Iron is extracted by heating a mixture of its ore and carbon.
Explain why electrolysis is used to extract aluminium but is not used to extract
iron.

Answer 5

An explanation linking
either
• aluminium high(er) in reactivity /
aluminium more reactive than
carbon / aluminium compounds
are very stable (1)
or
• iron lower in reactivity / iron less
reactive than carbon / iron
compounds less stable (1)
plus one of
• (for aluminium) electrolysis is
powerful means of reduction /
needs powerful means of
extraction / needs more energy
(1)
• (for iron) can be reduced with
{carbon / carbon monoxide} / use of
carbon is cheaper / use of electricity
is expensive / ORA (1)