Chemistry Reference
In-Depth Information
Checklist
After studying Chapter 10 you should know and understand
the following terms.
•
Alloy
Generally, a mixture of two or more metals (for
example, brass is an alloy of zinc and copper) or of a metal
and a non-metal (for example, steel is an alloy of iron
and carbon, sometimes with other metals included). They
are formed by mixing the molten substances thoroughly.
Generally, it is found that alloying produces a metallic
substance which has more useful properties than the
original pure metals it was made from.
•
Amphoteric hydroxide
A hydroxide which can behave as
an acid (react with an alkali) or a base (react with an acid),
for example zinc hydroxide.
•
Blast furnace
A furnace for smelting iron ores such as
haematite (Fe
2
O
3
) and magnetite (Fe
3
O
4
) to produce pig
(or cast) iron. In a modified form it can be used to extract
metals such as zinc.
•
Competition reactions
Reactions in which metals
compete for oxygen or anions. The more reactive metal:
•
takes the oxygen from the oxide of a less reactive metal
•
displaces the less reactive metal from a solution of that
metal salt - this type of competition reaction is known as
a displacement reaction.
•
Corrosion
The process that takes place when metals and
alloys are chemically attacked by oxygen, water or any other
substances found in their immediate environment.
•
Metal extraction
The method used to extract a metal
from its ore depends on the position of the metal in the
reactivity series.
•
Reactive metals are usually difficult to extract. The
preferred method is by electrolysis of the molten ore
(electrolytic reduction); for example, sodium from molten
sodium chloride.
•
Moderately reactive metals (those near the middle of the
reactivity series) are extracted using a chemical reducing
agent (for example carbon) in a furnace; for example,
iron from haematite in the blast furnace.
•
Unreactive metals, for example gold and silver, occur in
an uncombined (native) state as the free metal.
•
Metal ion precipitation
The reactions in which certain
metal cations form insoluble hydroxides. The colours of
these insoluble hydroxides can be used to identify the metal
cations which are present; for example, copper(ii)
ii
) hydroxide
is a blue precipitate.
•
Ore
A naturally occurring mineral from which a metal can
be extracted.
•
Reactivity series of metals
An order of reactivity,
giving the most reactive metal first, based on results from
experiments with oxygen, water and dilute hydrochloric
acid.
•
Recycling metals
Metal drink cans such as those made
of aluminium are collected in large 'banks' for the sole
purpose of recycling them. Reusing the metal in this way
saves money.
•
Rust
A loose, orange-brown, flaky layer of hydrated
iron(
iii
) oxide found on the surface of iron or steel. The
conditions necessary for rusting to take place are the
presence of oxygen and water. The rusting process is
encouraged by other substances such as salt. It is an
oxidation process.
•
Rust prevention
To prevent iron rusting it is necessary
to stop oxygen and water coming into contact with it. The
methods employed include painting, oiling/greasing, coating
with plastic, plating, galvanising and sacrificial protection.
