NCEA Level 3 Science (90730) 2011 — page 1 of 4
Assessment Schedule – 2011
Science: Describe selected organic compounds and their uses (90730)
Evidence Statement
Q
ONE
Evidence
Names of reactants are:
Methanol (an alcohol) and octanoic acid (a
carboxylic acid).
Name of ester formed is methyloctanoate.
Structure:
Equation
(Alcohol + carboxylic acid → ester + water)
Methanol + octanoic acid → methyl octanoate +
water.
Special conditions: Heated under reflux
conditions as reactants AND ester are volatile
and reflux allows heating for long enough for a
good yield of ester to be formed.
David Blaker & Sandy Talbett, NCEA Level 3
Science Study Guide (Auckland: ESA, 2005), p
105.
Concentrated sulfuric acid used as a catalyst to
speed up the reaction and also acts as a
dehydrating agent removing the water produced
in the reaction. This shifts the equilibrium to the
right (favours the forward reaction) resulting in
greater yield (amount) of ester produced.
Achievement
TWO of:
• Names reactants.
• Names ester.
• General word
equation.
• Draws ester.
• Names a
condition.
Eg: The reactants
are methanol and
octanoic acid. The
equation for an
ester is:
alcohol +
carboxylic acid 
ester + water
Achievement
with Merit
Draws ester,
specific word
equation
AND
Identifies either
special
condition.
Eg: The reactants
are methanol and
octanoic acid and
the ester that is
produced is
methyl
octanoate..
The ester is:
The equation for
this ester is:
methanol +
octanoic acid 
methyl octanoate
+ water
To produce more
ester, you can
add concentrated
sulfuric acid.
Achievement
with Excellence
ALL of:
• Draws ester
(condensed or
structural but
must show
ester link).
• Specific word
equation.
• Identifies
either special
condition
AND
Justifies their
use.
Eg: The reactants
are methanol and
octanoic acid and
the ester that is
produced is
methyl
octanoate.
The equation for
this ester is:
methanol +
octanoic acid 
methyl octanoate
+ water
To produce more
ester, you can
add concentrated
sulfuric acid. The
concentrated
sulfuric acid
works as a
dehydrating
agent and
removes the
water that is
produced in the
reaction. This
then drives the
reaction to the
products side and
therefore
increases the
yield of ester.
NCEA Level 3 Science (90730) 2011 — page 2 of 4
TWO
Functional group of double bond circled.
Triglyceride structure showing glycerol
backbone and 3 ester linkages to long chain fatty
acids.
Unsaturated alkenes are non-polar and dissolve
the non-polar grease and the hydrocarbon chain
of the fat molecules.
Orange oil contains limonene 90% an
unsaturated hydrocarbon. This acts as a solvent
for the fat and grease allowing it to be wiped
away whereas water, which is polar, does not
dissolve the non-polar grease.
Identifies
functional group.
OR
Structure of fat
molecule
described/drawn
but must specify
ester links and
fatty acid (long
chain).
AND
Description of
interaction of fats
and alkenes.
OR
Description of
effectiveness of
limonene on
grease.
OR
Description of
effectiveness of
water on grease.
Eg: Double bond
in the limonene
structure circled.
The limonene
cleaning product
will mix with the
fats and remove
them.
(polarity not
required, accept
wrong polarity if
consistent, eg
limonene is polar
so will dissolve
polar fat)
Identifies
functional group.
AND
Structure of fat
molecule
described/drawn
but must specify
ester links and
fatty acid (long
chain).
AND
Either:
Explanation of
interaction of
fats and alkenes
in terms of
polarity.
OR
Explanation of
effectiveness of
limonene on
grease in terms
of polarity.
OR
Explanation of
effectiveness of
water on grease
in terms of
polarity.
Eg: Both double
bond in the
limonene
structure circled.
The limonene
cleaning product
will act as a
solvent and mix
with the fats to
remove them.
This is because
the limonene is
non-polar and
the fats have a
non-polar tail.
Like dissolves
like.
All of:
Identifies
functional group.
Structure of fat
molecule
described/drawn
but must specify
ester links and
fatty acid (long
chain).
Explanation of
interaction of
fats and alkenes
in terms of
polarity.
AND
Comparison of
effectiveness of
limonene on
grease compared
to effectiveness
of water on
grease related to
polarity of
molecules
involved.
Eg: Both double
bond in the
limonene
structure circled.
The limonene
cleaning product
will act as a
solvent and mix
with the fats to
remove them.
The fats have a
non-polar tail in
their structure, so
will only
dissolve in a
non-polar solvent
(like dissolves
like). The
limonene is nonpolar whereas
water is polar.
This means that
water on its own
will not clean the
fats as easily as a
water limonene
mix.
NCEA Level 3 Science (90730) 2011 — page 3 of 4
THREE
Structure of detergent is long non-polar,
hydrophobic (water hating) hydrocarbon chain
with polar, hydrophilic (water loving) head.
David Blaker & Sandy Talbett, NCEA Level 3
Science Study Guide (Auckland: ESA, 2005), p
138.
Action on crude oil, micelle formation.
Structure of
detergent (labelled
diagram or
description).
OR
Action of
detergent
described.
Eg: The detergent
has a long nonpolar tail and polar
head:
Structure of
detergent.
AND
Action of
detergent
described. Must
say micelle and
describe the
polarity of oil
and tail OR
water and head.
Eg: The
detergent has a
long non-polar
tail and polar
head:
The detergent
mixes with the
oil slick and
breaks it down
into micelles. A
micelle has the
non-polar tail of
the detergent in
the non-polar oil,
and the polar
head sticking
out.
David Blaker & Sandy Talbett, NCEA Level 3
Science Study Guide (Auckland: ESA, 2005), p
142.
After treatment with detergent and solvents the
large oil mass is broken down into smaller oil
filled micelles which disperse due to wind and
wave action (and ultimately sink to the bottom of
the ocean where they are digested by
microorganisms).
NOTE: evidence for Achieve can be taken from
Question 2 if the structure of detergent is drawn
with reference to limonene.
FULL answer.
Structure of
detergent.
AND
Action of
detergent
described.
AND
Fate of oil given.
Eg: The
detergent has a
long non-polar
tail and polar
head:
The detergent
mixes with the
oil slick and
breaks it down
into micelles. A
micelle has the
non-polar tail of
the detergent in
the non-polar oil,
and the polar
head sticking out
into the polar
water. The oil is
surrounded by
detergent
molecules so the
oil slick gets
broken up and
dispersed
through the sea.
NCEA Level 3 Science (90730) 2011 — page 4 of 4
FOUR
Polymers are made up from monomers.
Polyethene is made from monomers of
ethene in an addition/polymerisation
reaction.
David Blaker & Sandy Talbett, NCEA Level
3 Science Study Guide (Auckland: ESA,
2005), p 87.
Low density polyethene (LDPE) has
branches on its polymer chains that prevent
the chains fitting closely, giving a more
open structure and a low boiling point
because the bonding between chains is not
as strong so requires less energy to break
these bonds. Flexibility is due to the open
structure.
High density polyethene (HDPE) has no
branched chains in the polymer chains so
more intermolecular (therefore stronger)
bonding between chains that require more
heat energy to break, resulting in higher
melting point and less flexibility, more rigid
structure.
THREE of:
• Monomer
named.
• Reaction
named.
• Equation
given.
• Identifies
presence of
branches in
LDPE.
Eg: This
reaction is
called
polymerisation
and the
monomer is
ethene.
All of:
• Monomer and
reaction named.
• Equation given.
• Compares
presence of
branches in
LDPE to lack of
branches in
HDPE.
Eg: This reaction is
called
polymerisation and
the monomer is
ethene.
The LDPE has
branches, whereas
the HDPE has no
branches, which
results in the
differing
properties.
Monomer and reaction
named.
Equation given
AND
Compares presence of
branches in LDPE to
lack of branches in
HDPE linked to
properties of each.
Eg: This reaction is
called polymerisation
and the monomer is
ethene.
The LDPE has
branches, whereas the
HDPE has no branches,
which results in the
differing properties.
The branches in the
LDPE mean the
polymers don’t pack
together as easily, and
therefore would have
less bonding between
chains so less energy is
required to break these
bonds, resulting in a
lower boiling point and
an increase in
flexibility. The absence
of branches in the
HDPE mean the
polymers pack together
more easily, and
therefore would result
in a higher boiling
point and a decrease in
flexibility. This is
because there would be
stronger bonds between
the strands that would
require more heat
energy to break these
bonds, therefore a
higher boiling point.
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
2A
2M
2E