NCEA Level 1 Chemistry (90648) 2010 — page 1 of 4
Assessment Schedule – 2010
Chemistry: Describe properties and reactions of carbon and its compounds (90648)
Evidence Statement
Q
Evidence
Achievement
ONE
(a)
Sugars such as glucose (also fructose and
sucrose) are converted into energy,
ethanol and carbon dioxide.
Yeasts perform the fermentation process
under anaerobic conditions (without
oxygen).
THREE of:
 Identifies the
reactants (sugar
and yeast) for the
fermentation
process or
identifies the
requirements
(anaerobic) for
the fermentation
process.
Glucose  ethanol + carbon dioxide gas
+ energy
C6H12O6  2C2H5OH + 2CO2 + energy
(c)(i)
(ii)
ethanoic acid (or acetic acid)
Methanol reacts with oxygen in both
types of combustion.
Complete combustion requires plenty of
oxygen, producing carbon dioxide and
water.
Incomplete combustion occurs when there
is insufficient oxygen present for
complete combustion to occur, and
produces carbon (or soot) / carbon
monoxide and water.
CH3OH +
3
O2  CO2 + 2H2O
2
Or
2CH3OH + 3O2  2CO2 + 4H2O
(iii)
Achievement with
Excellence
Identifies the
reactants OR
requirements for
the fermentation
process.
Identifies the
reactants AND
requirements for the
fermentation process.
AND
AND
Both structural
formulae correctly
drawn.
Both structural
formulae correctly
drawn.
AND EITHER
AND
Links both
complete and
incomplete
combustion
reactions to the
products formed
AND writes a
balanced equation
for the complete
combustion of
methanol.
Links both complete
and incomplete
combustion reactions
to the products
formed AND writes
a balanced equation
for the complete
combustion of
methanol.
OR
AND
Explains ONE way
carbon dioxide
impacts on the
environment.
Eg:
 increased levels
of CO2 trap heat
causing the
greenhouse
effect which has
led to global
warming.
Discusses TWO
ways carbon dioxide
impacts on the
environment.
Eg:
 increased levels of
CO2 trap heat
causing the
greenhouse effect
which has led to
global warming
and has caused sea
levels to rise with
melting ice caps.
 Draws the
structural formula
for ethanol.
(b)(i)
(ii)
Achievement with
Merit
The part carbon dioxide plays in
environmental processes.
Photosynthesis
Green plants convert carbon dioxide and
water into food compounds, such as
glucose, and oxygen. This process is
called photosynthesis. The food and
oxygen made are used by all living things
for respiration.
Influence of carbon dioxide on alkalinity
Carbon dioxide can change the pH of
water. Carbon dioxide dissolves slightly
in water to form a weak acid called
carbonic acid-CO2 + H2O  H2CO3
 Identifies and
draws the
structural formula
for ethanoic acid.
 Identifies
requirements for
each type of
combustion.
 Identifies
complete and
incomplete
combustion
products.
 Writes a balanced
equation for the
complete
combustion of
methanol
 Identifies an
effect that CO2
has on the
environment.
NCEA Level 1 Chemistry (90648) 2009 – page 2 of 4
pH can drop from 7 to 5.5
In the atmosphere
Greenhouse gases absorb some of the heat
from the sun and trap it so that the earth is
warmed up. This process is commonly
known as the greenhouse effect.
Carbon dioxide is a major greenhouse
gas. Increasing amounts of this have
added to the greenhouse effect and is
known as global warming. This may
cause increases in storm activity, melting
of polar ice caps, which will cause
flooding of the continents etc.
Complete combustion
CO and C soot from incomplete
combustion have detrimental health
effects on humans (CO
poisoning/haemoglobin and asthma from
soot). CO2 is not as toxic and more energy
efficient.
NCEA Level 1 Chemistry (90648) 2009 – page 3 of 4
TWO
(a)
Structures:
TWO of:
EITHER:
 Structure of
diamond is
drawn or
described.
 Structure of
graphite is drawn
or described.
Diamonds are made up of atoms
covalently bonded in a 3-dimensional
structure. Unlike graphite, diamond has
no weak intermolecular forces that are
easily broken.
 ONE relevant
property of each
of diamond and
graphite is
identified.
Links the relevant
properties (hard /
strong) of diamond
to its structure and
use in microbearings
Demonstrates an
understanding of
how the structure of
diamond determines
the properties (hard /
strong won’t break)
that make it useful in
micro-bearings.
OR
Links the relevant
properties (layers
slide/weak forces)
of graphite to its
structure and use
as a lubricant.
Graphite is made up of layers of
covalently bonded carbon atoms. The
layers are held together by weak
intermolecular forces.
(b)
Diamonds are made up of atoms
covalently bonded in a 3-dimensional
structure to form a giant network. Unlike
graphite, diamond has no weak
intermolecular forces that are easily
broken. Since the covalent bonds are very
strong and take a lot of energy to break.
This means that diamonds are extremely
hard and durable so can be used in microbearings even as very small balls. They
work in the same way that steel ball
bearings work by reducing the friction
that occurs between moving parts and
preventing them from getting damaged.
Graphite is made up of layers of
covalently bonded carbon atoms which
form a giant network. The layers are held
together by weak intermolecular forces.
These are easily broken when pressure is
applied or as parts move over each other
and reform when the movement stops.
This allows graphite to be used as a dry
lubricant that reduces friction between
moving parts.
(Note: If state
weak forces due to
delocalised
electrons merit
only)
AND
Demonstrates an
understanding of
how the structure of
graphite determines
the properties (layers
slide / weak
intermolecular
forces) that make it a
good lubricant.
(Note: Covalent
networks need only
to be mentioned for
one but can be
implied for the other,
eg layers.)
NCEA Level 1 Chemistry (90648) 2009 – page 4 of 4
THREE
Carbon dioxide dissolves in water in
small amounts making the water slightly
acidic as it forms carbonic acid, H2CO3.
The pH of Lake Nyos will be less than 7.
CO2 is less soluble at higher temps and as
the lake is volcanic it may have heated up
and therefore more gas was released.
CO2 is a colourless odourless gas. When
it was released from the lake, the people
and animals living nearby would not have
been able to see or smell it so wouldn’t
know they were in danger.
The gas is also more dense than air so
would have stayed close to the ground,
and flowed down the sides of the volcano,
depriving people and animals of air so
they would have died from suffocation /
asphyxiation.
Because carbon dioxide displaces oxygen,
it is a health risk since we need oxygen to
live. CO2 is an asphyxiant. It can cause
headaches, drowsiness and loss of ability
to maintain concentration.
Describes TWO
different properties
of carbon dioxide
gas.
Eg, acidic or dense
or colourless or
odourless or slightly
soluble.
OR
Describes ONE
property and a
symptom CO2 can
cause in people.
Eg, asphyxiant /
death.
Links TWO
properties of
carbon dioxide to
an effect from the
Case Study.
Eg
 acidic when
dissolved so
lowers lake pH warmer water,
more CO2
released as less
soluble
 dense so flowed
down mountain
displacing
oxygen odourless or
colourless so
wasn’t noticed.
Discusses TWO
effects of CO2 in the
Case Study in terms
of the relevant
properties.
Eg:
 acidic when
dissolved so
lowers lake pH as
forms carbonic
acid
 dense so flowed
down mountain
and displaced
oxygen and caused
suffocation
 odourless or
colourless so
wasn’t noticed so
people couldn’t
avoid it.
OR
AND
Links ONE
property of carbon
dioxide to an effect
from the Case
Study.
AND
Discusses why
carbon dioxide has a
dangerous impact on
human (or animal)
health.
Eg, asphyxiant /
death.
Explains why
carbon dioxide has
a dangerous
impact on human
(or animal) health.
Eg, asphyxiant /
death.
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
2A
2M
2E