This document discusses the chemical composition of different parts of the natural environment including the atmosphere, hydrosphere, lithosphere, and biosphere. It explains that the atmosphere contains molecular elements like oxygen and compounds like carbon dioxide. The hydrosphere mainly contains water along with dissolved ionic compounds like sodium chloride. The lithosphere contains minerals composed of elements like silicon and oxygen. The biosphere contains large organic molecules like carbohydrates, proteins, and DNA composed of carbon, hydrogen, oxygen, and nitrogen. The document also discusses the properties of molecular and ionic compounds as well as extraction of metals from ores.

1. MODULE C5: CHEMICALS OF THE
NATURAL
ENVIRONMENT

2. Atmosphere
• Molecular
elements (e.g.
oxygen,
nitrogen, ozone)
and compounds
(e.g.carbon
dioxide, water)
• Monoatomic
elements (e.g.
argon)
hydrosphere
• Mainly water
plus…
• Solution of ionic
compounds (e.g.
sodium chloride)
Q. Give the chemical symbols and state symbols for all the chemicals above.

3. Properties
Molecular
compounds
Ionic
compounds
Made from Two or more non-metal
atoms bonded
Metal ions with non metal
ions
Electrical
properties
Insulators (no ions!) Conduct only when molten
or dissolved in water
Forces
holding them
together
Strong covalent bonds
within the molecule but
weak forces between
molecules
Strong attractions between
oppositely charged ions
Melting and
boiling points
Low… found as gases at
room temperature
High… found as solids or
in solution

4. Formulae of salts
• Metal ions (+) combine with non-metal
ions (-) to form neutral compounds.
• The formula of magnesium oxide is
MgO
• The formula of sodium oxide is Na2O
Mg 2+
Mg 2+
Mg 2+
Mg 2+
Mg 2+
Mg 2+
O 2-
O 2-
O 2-
O 2-
O 2-
Mg 2+
O 2-
Na +
O 2-
Na +
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
O 2-
Find the formula of… aluminium with fluorine,
calcium with chlorine, sulphur with potassium
The group number of the
atom can tell us which ion it
will form..
group ion
1 1+
2 2+
3 3+
4 None
5 3-
6 2-
7 1-
0 None

5. Lithosphere
• Made of the crust and
upper mantle
• Composed of minerals
e.g. quartz containing
silicon dioxide found in
granite and sandstone
• Rich in the atoms of
silicon, oxygen and
aluminium
Treasures of the Earth:
Gemstones for beauty, hardness, rarity

6. Chemical Brothers
• Carbon dioxide and silicon dioxide are both covalently bonded
compounds but with very different physical properties
Carbon dioxide Silicon dioxide
Molecular structure (limited
covalent bonding)
Giant structure (more extensive
covalent bonding)
Low melting point High melting point
insulator Semi-conductor
gas Hard solid
Soluble in water Insoluble in water
negatively charged electrons are
attracted to the positively charged
nuclei to form strong covalent
bonds

7. Biosphere
• the total sum of living organisms
• Contains large molecules such as
fats, carbohydrates, proteins, DNA
• Mostly: carbon, hydrogen, oxygen,
nitrogen
• Minor contributions from phosphorus
and sulphur
What’s the formula of the glucose
molecule above?

8. Cycling of
nutrients
• Many elements
are cycled in
nature including
carbon, nitrogen
and oxygen.
• Identify in the
cycle opposite
where carbon
can be found
as… (i) simple
molecular
compounds, (ii)
large molecules
and (iii) as the
element

9. Extracting metals
• For zinc, iron and copper (fairly un-reactive metals)
the ore (often an oxide) is mined, concentrated then
the metal is extracted by heating with carbon
Copper oxide + carbon copper + carbon dioxide
lost oxygen gained oxygen
When oxygen is lost: REDUCTION
When oxygen is gained: OXIDATION
Overall the process is REDOX
Re-write the equation above using symbols (chemical and
state symbols!)
Write out the equivalent equation for iron (III) oxide (where iron
has a 3+ charge)

10. Extracting reactive metals
• The oxides of the more reactive metals are very stable so they
require large amounts of energy supplied by electricity in order to
extract the metal. The electricity decomposes the compound into
simpler substances.
Electrolyte: aluminium oxide
(bauxite) with cryolite added

11. … in more detail
• The cryolite
makes the
aluminium oxide
(bauxite) easier to
melt so the ions in
it are free to move
to each electrode
to become neutral
atoms
Al 3+
Al 3+
Al 3+
O 2-
O 2-
O 2-
cathode
anode oxygen
gas
released
Molten
aluminium
metal drops
to the
bottom
Use an ionic equation to show what happens at each electrode

12. Metals
• The typical properties of high melting/
boiling points, high strength, malleable
and conduction of heat/ electricity can all
be explained by their structure
M + M +
M +
M +M + M +
M +
M + M +
Giant structure held together by ionic bonding
Metal ions in a lattice
Sea of electrons (free to move)

13. Environmental issues
• The (i) mining, (ii) extraction,
(iii) transport, (iv) maintenance
and (v) disposal of metals all
have an impact on the
environment.
• For each stage above suggest how
it may affect the surroundings