594446
C5 - Chemicals of the
Natural Environment
- Atmosphere - COVALENT
(sharing)
- the chemicals consist of
non-metal elements and
molecular compounds from
non-metal elements
- gases consist of small
molecules with weak forces of
attraction between the
molecules. so, a small amount
of energy is needed to break
these forces, allowing
molecules to move freely
through air.
- gases consist of small
molecules with weak forces of
attraction between the
molecules. so, a small amount
of energy is needed to break
these forces, allowing
molecules to move freely
through air.
- molecules (exception of water) are
gases at room temperature and have
low boiling points - molecular
structures. MOLECULAR
COMPOUNDS HAVE STRONG
COVALENT BONDS BETWEEN
THE ATOMS but WEAK FORCES
OF ATTRCATION BETWEEN THE
SMALL MOLECULES
- In covalent binds, the
electrons are shared
between the nuclei of
two atoms. this causes
a strong electrostatic
attraction between the
nuclei and shared
electrons
- In covalent binds, the
electrons are shared
between the nuclei of
two atoms. this causes
a strong electrostatic
attraction between the
nuclei and shared
electrons
- the chemicals consist of
non-metal elements and
molecular compounds from
non-metal elements
- Lithosphere
- a mixture of minerals, such as
silicon dioxide (SiO2)
Abundant elements include:
Silicon (Si), Oxygen (O2) and
Aluminium (Al). much of the
silicone and oxygen are
present as silicon dioxide
- silicon dioxide forms a GIANT
COVALENT STRUCTURE. here, each
silicon atom is covalently bonded to 4
oxygen atoms
- each oxygen atom is
bonded to 2 silicon
atoms. the result is a
very strong rigid three
structure
- silicon dioxide doesn't does
not conduct electricity as
there are no ions or free
electrons in the structure. it
doesn't dissolve in water
because there are no charges
to attract water molecules. it
also has high melting and
boiling points
- silicon dioxide exists in
different forms such as
quartz in granite and it is
the main constituent of
sandstone,
- Amethyst is a form of quartz that is used in
jewelry. the violet colour comes from traces of
magnesium oxide and iron oxides found in the
quartz. some gemstones are very valuable because
of their rarity, hardness and shiny appearance
- silicon dioxide exists in
different forms such as
quartz in granite and it is
the main constituent of
sandstone,
- silicon dioxide doesn't does
not conduct electricity as
there are no ions or free
electrons in the structure. it
doesn't dissolve in water
because there are no charges
to attract water molecules. it
also has high melting and
boiling points
- each oxygen atom is
bonded to 2 silicon
atoms. the result is a
very strong rigid three
structure
- Carbon is another example of
a mineral that forms a giant
covalent structure. 2 forms of
carbon are:
- Diamond
- large number of covalent bonds - high melting and boiling
points. each carbon atom is covalently bonded to 4 other
carbon atoms - results in a very strong, rigid 3D structure
that is difficult to break down. Diamond is insoluble because
there are no charges to attract water molecules. it doesn't
conduct electricity because there are no ions or free
electrons in the structure
- large number of covalent bonds - high melting and boiling
points. each carbon atom is covalently bonded to 4 other
carbon atoms - results in a very strong, rigid 3D structure
that is difficult to break down. Diamond is insoluble because
there are no charges to attract water molecules. it doesn't
conduct electricity because there are no ions or free
electrons in the structure
- Graphite
- a form of carbon that has a giant
covalent structure,. each carbon
atom is covalently bonded to three
other carbon atoms in a layered
structure. the layers can slide over
each other making it soft and
slippery
- Enter text here
- Enter text here
- a form of carbon that has a giant
covalent structure,. each carbon
atom is covalently bonded to three
other carbon atoms in a layered
structure. the layers can slide over
each other making it soft and
slippery
- Diamond
- silicon dioxide forms a GIANT
COVALENT STRUCTURE. here, each
silicon atom is covalently bonded to 4
oxygen atoms
- a mixture of minerals, such as
silicon dioxide (SiO2)
Abundant elements include:
Silicon (Si), Oxygen (O2) and
Aluminium (Al). much of the
silicone and oxygen are
present as silicon dioxide
- Hydrosphere -
IONIC (+ve,-ve)
- dissolved ionic compounds
(making water taste salty)
are:
- Sodium Chloride - NaCl
- Magnesium Chloride - MgCl2
- magnesium sulphate - MgSO4
- sodium sulphate - Na2SO4
- potassium chloride - KCl
- potassium bromide - KBr
- potassium bromide - KBr
- potassium chloride - KCl
- sodium sulphate - Na2SO4
- magnesium sulphate - MgSO4
- Magnesium Chloride - MgCl2
- water has some unexpected
properties - boiling point is 100 - much
higher than the other molecules.
WATER IS ALSO A GOOD SOLVENT
FOR SALTS - PROPERTIES
EXPLAINED BY ITS STRUCTURE
- the water molecule is bent - the
electrons in the the covalent bond are
nearer to the oxygen atom than the
hydrogen atoms. this results in a polar
molecule.
- the top is slightly negative and the bottom is
slightly positive. the small charges on the
atoms mean that the forces between the
molecules are SLIGHTLY STRONGER THAN
IN OTHER COVALENT MOLECULES. - more
energy is needed to seperate them.
- smaller charges also
help water to dissolve
ionic compounds as the
water molecules attract
the charges on the ions -
ions can move freely
through the liquid.
- smaller charges also
help water to dissolve
ionic compounds as the
water molecules attract
the charges on the ions -
ions can move freely
through the liquid.
- the top is slightly negative and the bottom is
slightly positive. the small charges on the
atoms mean that the forces between the
molecules are SLIGHTLY STRONGER THAN
IN OTHER COVALENT MOLECULES. - more
energy is needed to seperate them.
- the water molecule is bent - the
electrons in the the covalent bond are
nearer to the oxygen atom than the
hydrogen atoms. this results in a polar
molecule.
- Sodium Chloride - NaCl
- ions in ionic compounds can
be detected and identified as
they have distinct properties
and form chemicals with
distinct properties.
- e.g. an insoluble compound
may precipitate on mixing 2
solutions of ionic compounds
- this technique is often used to
identify metal ions.
- in this example, a white precipitate of calcium
hydroxide is formed as well as sodium chloride
solution. Ca2+ + 20H- -> Ca(OH)2
- in this example, a white precipitate of calcium
hydroxide is formed as well as sodium chloride
solution. Ca2+ + 20H- -> Ca(OH)2
- this technique is often used to
identify metal ions.
- e.g. an insoluble compound
may precipitate on mixing 2
solutions of ionic compounds
- in the oceans, dissolved
calcium ions and carbonate
ions combine to form a
precipitate of calcium
carbonate - limestone which
falls to the sea floor.
- in order to identify a negative
ion, a range of different tests
may be carried out, involving
adding a reagent to an unknown
sample - reacts with the ions to
form an insoluble salt.
- to identify the presence of a
sulfate ion, add barium chloride
solution and dilute HCl to the
suspected sulfate solution. - A
WHITE PRECIPITATE OF
BARIUM SULFATE WILL BE
PRODUCED IF A SULFATE IS
PRESENT,
- Chloride, Bromide and Iodide Ions - to
identify the presence of these, add
silver nitrate solution and nitric acid to
the suspected halide solution - A
WHITE PRECIPITATE WILL FORM IF
SILVER CHLORIDE IS PRESENT;
CREAM PRECIPITATE FOR SILVER
BROMIDE AND A YELLOW
PRECIPITATE FOR SILVER IODIDE.
- to identify the presence of a
sulfate ion, add barium chloride
solution and dilute HCl to the
suspected sulfate solution. - A
WHITE PRECIPITATE OF
BARIUM SULFATE WILL BE
PRODUCED IF A SULFATE IS
PRESENT,
- In general, most ionic compounds
are soluble in water but there are
some exceptions.
- dissolved ionic compounds
(making water taste salty)
are:
- extracting useful metals from minerals
- structure and properties of metals
- testing for carbonates
- testing with acids
- carbonates react with dilute acids
to form carbon dioxide gas and a
salt and water. e.g. if we add
calcium carbonate to dilute
hydrochloric acid, the carbonate will
FIZZ, giving off carbon dioxide. so,
the dilute acid and carbonate will
turn lime water milky.
- thermal
decomposition
- when copper carbonate and zinc
carbonate are heated, thermal
decomposition takes place - resulting
in a distinctive color change, enabling
the 2 compounds to be identified.
- strongly heating copper
carbonate in a combustion
tube causes it to go black
as copper oxide is formed.
- strongly heating zinc carbonate in a
combustion tube causes it to go yellow as
zinc oxide is formed. the yellow colour is
only seen at high temperatures as it is of a
different cystalline form. when it cools, the
zinc carbonate turns white
- strongly heating copper
carbonate in a combustion
tube causes it to go black
as copper oxide is formed.
- when copper carbonate and zinc
carbonate are heated, thermal
decomposition takes place - resulting
in a distinctive color change, enabling
the 2 compounds to be identified.
- carbonates react with dilute acids
to form carbon dioxide gas and a
salt and water. e.g. if we add
calcium carbonate to dilute
hydrochloric acid, the carbonate will
FIZZ, giving off carbon dioxide. so,
the dilute acid and carbonate will
turn lime water milky.
- testing with acids
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