NCEA Level 2 Science (90766) 2010 — page 1 of 2
Assessment Schedule – 2010
Science: Describe the chemical properties and effects of fertilisers (90766)
Evidence Statement
Question
ONE
Achievement
Achievement with Merit
Achievement with Excellence
Charged (not polar) water molecules
separate the ammonium and sulfate
ions from each other, and the solid
breaks up.
Charged water molecules
separate the ammonium and
sulfate ions from each other, and
the solid dissolves / breaks up.
AND
Positive parts of water molecule
surround the negative ion
(sulfate ion) OR
negative parts of the water
molecule surround the positive
ion (ammonium ion).
Charged water molecules separate
the ammonium and sulfate ions
from each other, and the solid
dissolves.
AND
Positive parts of the water
molecule surround the negative
ion (sulfate ion).
AND
Negative parts of the water
molecule surround the positive
ion (ammonium ion).
AND/OR
The charged ions are no longer so
attracted to each other due to the
water molecules surrounding
them.
Evidence for Achievement can come
from a labelled diagram.
Evidence for Merit can come
from a labelled diagram.
Evidence for Excellence can
come from a labelled diagram.
TWO
Description of an aspect of water
quality (nutrients and levels/levels of
aquatic plants/O2 levels/CO2
levels/numbers of aquatic animals)
for both Lake Hayes and Wakatipu.
Explains the water quality in one
lake.
Eg:
Because of the high levels of
phosphates and nitrates in Lake
Hayes, the aquatic plants are
fertilised and grow, resulting in
an algal bloom. As these plants
die, microorganisms cosume
oxygen, leading to low levels of
dissolved oxygen in Lake
Hayes, which means aquatic life
is adversely affected.
Discussion of the water quality in
Lake Hayes and Lake Wakatipu.
Eg:
Because of the high levels of
phosphates and nitrates in Lake
Hayes, the aquatic plants are
fertilised and grow, resulting in
an algal bloom. As these plants
die oxygen is consumed, leading
to low levels of dissolved oxygen
and increasing CO2 levels in Lake
Hayes, which means aquatic life
is adversely affected.
Lake Wakatipu has low levels of
phosphates and nitrates, which
means there are low levels of
aquatic plants and high levels of
dissolved oxygen. Aquatic
animals have an optimal
environment to live in.
NCEA Level 2 Science (90766) 2010 — page 2 of 2
THREE
Blue flowers occur in pH below 7.
OR
Blue flowers occur when excess of H +
ions.
OR
Add an acidic fertiliser.
(Note: error in colour here does not
affect M answer.)
Add a fertiliser that releases H+
ions and lowers the pH
OR
NH4+ in ammonium sulfate reacts
with water to give H+, meaning
pH below 7.
OR
NH4+ + H2O = NH3 + H3O+
Add an acidic fertiliser to
change pH to below 7.
OR
Add a fertiliser with H+ in it to
provide an excess of H+ ions.
OR
More H+ ions in the soil means
pH below 7.
OR
Add a fertiliser such as
ammonium sulfate to make soil
acidic.
Must refer to blue flowers at
lower pH.
TWO points linked.
FOUR
% K partially correct, eg =
39 100
´
= 22%
174
1
K2SO4
M = 174
78 100
´
%K=
174
1
= 45%
Potassium chloride has 52%
potassium and potassium sulfate
has 45% therefore potassium
chloride has higher potassium
percentage and so better for a
crop.
Potassium chloride has 52%
potassium and potassium sulfate
has 45% therefore potassium
chloride has higher potassium
percentage and so better for a
crop. In 1 kg of potassium
chloride there are 520 g of
potassium compared to 450 g of
potassium from potassium sulfate.
Potassium chloride provides more
potassium per kilogram.
Allow follow on error for Merit
only.
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
3A
OR
2M
3M
2E+1M