Download Ocean Acidification Lab Report - APES -

Bao Nguyen
09/17/14
Period 1
Ms.Ogo
The Effect of Carbon Dioxide on Acidity of Saltwater
On our planet, the Carbon cycle is a substantial geochemical cycle to the survival of
all organisms. The cycle begins with phytoplankton on the ocean surface absorbing the
carbon in the atmosphere along with sunlight to perform photosynthesis. When the
organisms die or release waste, their matters sink to the bottom of the ocean which
decompose into the Earth’s crust as fossil fuel and sedimentary rock. Eventually, extreme
heat and pressure will cause the CO2 to return to the atmosphere as volcanic gas.
In nature, it takes millions of years for the amount of fossil fuel we have already used
to accumulate in the Earth’s crust. Industrial development leads to the excessive burning
of fossil fuel, which incessantly contributes CO2 to the atmosphere. Although the ocean
is a carbon sink, it can’t sequester the disproportionate CO2 in the air. Therefore, much of
the CO2 enters the ocean and dissolves to form carbonic acid which causes ocean
acidification.
In this experiment, we aim to find out how CO2 affects the acidity of the ocean. We
will model the ocean with a beaker filled with 100ml of saltwater added with a few drop
of universal indicators to identify the pH. We will put the beaker on a white sheet of
paper to make the pH color clearly visible. The beaker’s mouth will then be covered up
with saran wraps. Lastly, we will poke a hole and insert a straw. A blower then begin
blowing steadily through the straw for 2 minutes while the observer records the pH
according to the color for every 30 seconds.
When we blow into the water, we are actually breathing out CO2. When the CO2
enters water, it dissolves to form carbonic acid. We are measuring the pH by observing
the universal indicator’s color and matching it to the pH scale. Measuring the pH will
tells us how the CO2 affect the water’s acidity. I believe that the carbonic acid will
disassociate in the water to form bicarbonate and hydrogen ion which will lower the pH
of the water. If I blew into the saltwater, then its pH would decrease.
There are a total of 4 protocol used in this experiment: control, A, B and C. The
control protocol is exactly as previously mentioned in the procedure. For protocol A, we
will use tap water instead of saltwater. For protocol B, the beaker will be placed on ice for
3 minutes and for protocol C, the beaker will rest on a heating plate for 3 minutes. The
independent variable is the time since how long we blow determines how much CO2 is
emitted. The type of solvent used, either saltwater or tap water is also an independent
variable. Another independent variable is the temperature of the liquid. The dependent
variable for all protocol will be the pH and the color of the water. The constant is the
amount of solvent: 100ml.
Data Table-Bubble Protocol
Properties/Times
0:00 (0s)
0:30 (30s)
1:00 (60s)
1:30 (90s)
2:00 (120s)
Control
pH
7
7
6.5
6.5
6.5
Protocol
Color
Green
Green
Light Green
Light Green
Light Green
Protocol
pH
7.25
7
6.5
6
6
A
Color
Dark Green
Green
Light Green
Yellow
Yellow
Protocol
pH
7
6.5
6.5
6.5
6.5
B
Color
Green
Light Green
Light Green
Light Green
Light Green
Protocol
pH
7.25
7.25
7
7
6.5
C
Color
Dark Green
Dark Green
Green
Green
Light Green
As I blew through the straw, more CO2 was being added to the water which dissolve
to form carbonic acid. Carbonic acid disassociates and release bicarbonate ions and
hydrogen ions into the water which lower the pH. The universal indicator shows that an
increase in CO2 means a drop in the pH level. This shows that the carbonic acid released
from CO2 in the atmosphere has a significant impact on the ocean’s acidity. Based on the
experiment, the taps water affects the pH the most. The tap water is the only one out of all
protocol that managed to reach 6 on the pH scale.
My initial hypothesis was correct. The pH of the water decreased after being blown
with the straw. In all protocol, the pH all decreased by at least .5 unit which shows that
the blowing in the water with CO2 does in fact acidifies the water. From this experiment,
I learned how something as simple as breathing could acidify water. This experiment
seems to simulate the current predicament of the ocean and the possible outcome in the
future. I realized that our current steadily increasing CO2 emission rate won’t take long
before it makes the entire world’s ocean acidic, exactly as this experiment portrays.
The Effect of Acidic Water on Sturdiness of Shells
Marine organisms use calcium carbonate from mineral deposit as the basic building
block of their shell and external skeleton. Regarding this experiment, if the shell was to
submerge in the vinegar, then it would most likely corrode over time and become more
fragile and brittle. Carbon dioxide as previously stated naturally come from volcano but
human’s usage have led to excessive CO2 emission coming from mine, oil drilling, etc. I
hypothesize that placing the clam in vinegar will make it handle less weight than the clam
placed in saltwater.
In this experiment, there are two essential protocols that uses two mussel clams. In
the control protocol, we prepare a beaker with saltwater and in the experimental protocol,
we prepare a beaker with vinegar. The two clams will immerse in the liquid at the same
time for 30 minutes and will also be removed at the same time. In both protocol, the
initial mass is the independent variable. Also an independent variable is the time and the
solution: saltwater or vinegar. The constant is the 150ml solution of liquid. There are also
two additional pre-treated clams that will simply be observed and tested for strength. The
dependent variable for all clams is the final mass and the numbers of book they can lift
without breaking.
Data Table - Shell Protocol
Property/Data
Observation
Initial
Mass
(grams)
Final
Mass
(grams)
Difference
(grams)
Endurance
(Books)
Control
Seawater
90% White
Grey color
3.1
3.1
0
17
Experimental
Vinegar
Lots of Bubble
Broken Piece
Distorted Color
2.8
2.7
0.2
10
High
Exposure
Small Scratch
Brittle
Washed Out
2.4084
1.7
0.7080
2
Low
Exposure
Less Brittle
Broken Piece
2.2425
1.9
0.3425
4
As the experiment began, the shell immersed in vinegar produce immense bubbles
which signify a reaction was occurring. Another sign of interaction between the vinegar
and the shell was some small brittle piece on the shell was breaking off. Regarding nature,
this experiment demonstrates the way that acid, represented by vinegar, corrodes the shell
of organisms living in region with low pH. Lower pH means more acidic property which
constitutes a more caustic environment for organisms, hence why their shell are so brittle.
To these animals, having a proper shell protects them and allow for better survivability
and adaptation. It definitely cost a lot energy for organisms to rebuild their shells,
especially if the water is highly acidic which would corrode their shells even faster than
they could fix it.
Overall, this experiment confirmed my hypothesis that the clam treated in vinegar
will be more fragile than the one treated in saltwater. It could only withstand the weight
of 10 books as opposed to the control clam which handled the weight of 17 books. The
vinegar clearly corroded the clam as the bubbles seem to show, consequently making it
much weaker than the clam treated in saltwater. To conclude, this experiment verified
that the carbonic acid from CO2 would destroy the calcium carbonate shell of marine
organisms. This will hurt the primary production which will jeopardize the zooplankton
which then affects the larger carnivorous animals, some also depending on shell to
survive. In the end, ocean acidification would destroy ecosystem and the livelihood of our
economy because it heavily depends on fishing.