Causes and Effects of Acid Rain and Ocean Acidification
Fellow(s): Aaron Ferrel and Catalina Marambio Jones
Grade Level: 6th and 11-12th
Subject(s): Earth Science (6th), Environmental Science AP (11-12)
(picture taken by Carlene Daggett)
Summary:
This lesson examines the causes and effects of acid rain and ocean acidification as a result
of increased anthropogenic carbon dioxide.
Anthropogenic greenhouse gas emissions in the US are emitted through the burning of
fossil fuels in power plants and automobiles. During the combustion of fossil fuels such as
coal and gasoline, byproducts such as carbon dioxide, nitrogen oxides, and sulfur oxides are
generated. These gases combine with cloud water droplets to increase the acidity of the
rain. Acid rain can disrupt freshwater ecosystems. Additionally, calcium carbonate in
buildings and roads is easily dissolved by acid rain. Moreover increased atmospheric CO2
affects the acid base balance in oceans. In fact the ocean’s pH has decreased a measurable
amount since pre-industrial revolution. Given that the pH is very important in the
formation of CaCO3 (also called calcite), the change in pH affects the capacity of many
marine organisms to form exoskeletons (made mainly of CaCO3) and is also one of the
causes of bleaching of coral reefs.
Time Required: One 90 minute class (6th grade) or two 50 minute classes (11-12 grade)
Group Size: 3-4
Cost to implement:
 Dry ice: ~$1/pound. About 10 pounds were enough for all the class periods in one
morning.
 Baking soda: ~$3/pound
 Universal pH indicator: $22/500 mL (in Fisher scientific for science education
quality grade).
 vineger:~ $3/gallon (Smart&Final)
 Chalk ~ $1
Learning Goals:
Students should be able to:
1. Understand the pH scale, understand concept of acid or base
2. Explain the combination of carbon dioxide and water forms acid rain
3. Explain how acid affects calcium carbonate
4. Relate these concepts two possible effects on life in the ocean
Level of Inquiry:
Based on background information about the carbon cycle and the pH scale, the students
will hypothesize as to what happens to water mixed with carbon dioxide and subsequent
effects on CaCO3.
Introduction / Motivation:
There are three things that need to be introduced: the carbon cycle, the pH scale and
buffer capacity. First, we explain how fossil fuels are formed, and how burning those
releases carbon dioxide. We introduce the carbon cycle as storage and exchange of carbon
between various reservoirs on earth. A good starting point is to explain that plants and
animals exchange carbon dioxide between the land and atmosphere via photosynthesis and
respiration. We expand this into the ocean, where mixing happens naturally, as well as
marine life photosynthesis and respiration (can use Plankton from SpongeBob). To begin
the pH scale discussion, we first list some common liquids and whether or not they are
acidic or basic, so the students realize that acids and bases are all around us. Also this
dispels the idea that all acids eat flesh (this is mostly for 6th graders). Furthermore, we
describe how the pH of a solution is a function of [H+] and [OH-] with an activity where the
students count the number of H+ and OH- ions in a picture and determine if it is an acid or
base. Then we introduce the pH scale where the number tells you if it is an acid or base.
After that, we talk about the buffer capacity of water. Alkalinity provides a buffer against
pH. A good way to relate this to the students is to say alkalinity is like pacman eating the
little spheres. If we put H+ in water, then pacman/alkalinity will consume some of the H+,
decreasing its availability and therefore buffering the decrease in pH.
The overall motivation for this is that increased anthropogenic carbon dioxide is
making the rain, as well as, freshwater and saltwater bodies more acidic. This will have a
plethora of negative effects, with the most significant being the dissolution of calcium
carbonate that is contained in buildings and the shells of living organisms. Some bodies of
water are able to resist the change in pH because they have significant buffer capacity.
Lesson Background Concepts for Teachers:
Anthropogenic carbon dioxide is released into the atmosphere by combustion of
fossil fuels. Carbon dioxide leads to global warming. Additionally, the combination of
carbon dioxide and water forms carbonic acid, which lowers the pH of rain and bodies of
water. Carbon dioxide exchange is naturally balanced between the atmosphere, land and
ocean. When humans introduce extra carbon dioxide, oceanic carbon dioxide increases
forming carbonic acid.
pH definition: pH = -log[H+], where [H+] is the molar concentration of H+ ions in
solution.
Acids give H+ to solution, therefore increasing [H+], which lowers pH. Carbonic acid
lowers the pH of the ocean. Decreased pH promotes dissolution of calcium carbonate
(shifts the reaction CaCO3Ca2++CO32- to the right). Given that phytoplankton, coral, and
other marine organisms structures are made of calcium carbonate, the dissolution of this
compound generates severe injuries. Similarly, acidic rain dissolves calcium carbonate
found in buildings, roads and other structures leading to a slow but constant degradation.
The buffer capacity of a solution is the ability of the solution to resist changes in pH.
Buffers neutralize acid in a solution, generally leaving water and a salt. Buffer capacity
depends on alkalinity. The more alkaline a solution is, the more acid is required to lower
the pH. Likewise, a lower alkalinity requires less acid to lower the pH.
Procedure:
1) Presentation (20 min): Background information on acid rain and ocean acidification.
Concepts of pH scale, carbonate cycle and buffer capacity will be explained.
2) pH determination of different liquids using universal pH indicator (20-30 min)
a) For 6th graders: First from previous knowledge students list the liquids from
acidic to basic. Second, students measure liquid’s pH with universal pH indicator
(this part can be developed as a guided demonstration). Third, they color a chart
with the respective color and determine the pH. Finally, students review their initial
hypothesized list and correct if necessary.
b) For 11-12th graders: Students will drop solution in well plates. After that, they
will insert universal pH indicator in each solution and determine the pH from a color
chart. After wards, they will calculate the [H+] for each solution and plot each on a
linear and logarithmic scale.
3) Effect of CO2 dissolution on water pH and the role of alkalinity: In this part of the
activity students will evaluate how the incorporation of CO2 affects the pH of different
samples with different levels of alkalinity. Additionally, they will study how the dissolution
of CaCO3 (chalk) is affected by the concentration of acid in the water. Six graders will do an
endpoint titration utilizing dry ice (CO2) to observe the change in pH while 11-12 graders
will perform and acid titration in solution with different alkalinity.
----------------------------------------Main Lab (6th graders):
1. Students hypothesized about what liquid will have more resistance to the
pH change and which liquid will cause more dissolution of CaCO3.
2. Students will be separated in groups of 3-4, and each group will be provided with
5 beakers with 100 mL the following: Beaker A) Solution with pH 8.5 and low
alkalinity (control), Beaker B) Solution with pH 8.5 and low alkalinity, Beaker
C)Solution with pH 8.5 and high alkalinity, Beakers D) 20% vinegar, Beaker E)tap
water. (Beakers A to C are for the first part of the activity and D and E for the
second).
3. Lab work, first part:
-They will add 10 drops of universal indicator to each beaker A to C and will take
note of the initial pH.
-Then, they will add walnut-size piece of dry ice to beakers B, C. After, all the dry ice
is dissolved the students will take note of the final solution color and will determine
the final pH from it and will compare to the control.
4. Lab work, second part
-Students will add a piece of Chalk (CaCO3) to beakers D and E and they will observe
where the chalk dissolves the fastest.
5. Students fill out a worksheet which includes questions (worksheet in list of
attachments)
--------------------------------Main lab (11-12 grade) (started at the end of day one and completed on day 2)
1. Students hypothesize about what liquid will have more resistance to the pH
change and which liquid will cause more dissolution of CaCO3.
2. Students will be separated in groups of 3, and each group will have 3 beakers: A)
Solution with pH 8.5 and low alkalinity (control), B) Solution with pH 8.5 and low
alkalinity, C) Solution with pH 8.5 and high alkalinity.
3. They will add 10 drops of universal indicator to each beaker and will take note of
the initial pH.
4. Students will add a pre weighted chalk stick (CaCO3) to each beaker and then
they will add same amount of dry ice(walnut size) to beakers B and C. After, all the
dry ice is dissolved the students will observed the dissolution of the calcium
carbonate and make observations on where does it dissolve the fastest. They will
then cover with parafilm the beakers and leave them for the next day.
(Second day)
5. In the second day. Students will remove (when possible) what is left from the
chalk in beakers A, B, C and they will measure the remaining weight.
6. Other 3 A, B, C beakers will be given to the students with their respective
solutions. Students will add universal pH indicator and then students will titrate
beakers B, C with acid and they will plot the pH versus the amount of acid added
(number of drops).
5. Through experience students fill out a work sheet which includes questions
----------------------------------Materials List:
Dry Ice
Tap water
Baking soda
Chalk
Vinegar
250mL Beakers
Droplet Pipettes
Tongs
Stir rods
Graduated cylinder
Each group will need:
 Five 250 mL beaker containg 100 mL of the following
o Beaker A : pH 8.5 and low alkalinity (Ex. Tap water with pH adjusted with a
base)
o Beaker B : pH 8.5 and low alkalinity
o Beaker C : pH 8.5 and high alkalinity (Ex. 1Tbsp baking soda to 1 gallon of tap
water, check pH to get 8.5)
o Beaker D : 20% vinegar
o Beaker E: Tap water
 Chalk pieces
 Stir rod
To share with the entire class:
 Dry ice in small pieces

Tongs
Safety Issues:
Use tongs, or appropriated globes to handle the dry ice. Do not touch it directly.
Lesson Closure:
Ask the students what observations they made and relate these to real things in the ocean.
Assessment:
Pre-Activity Assessment:
Ask them if they knew what carbon or fossil fuels are. Ask them if they knew what liquids
are acids and bases, and if they knew about pH.
Activity Embedded Assessment:
During lab, walked around to each group and asked for their observations and if they could
explain them.
Post-Activity Assessment:
A class discussion about the lab and revision of the plots (12 graders).
References (used for inspiration and information):
1. http://www.epa.gov/acidrain/
2. http://jrscience.wcp.muohio.edu/fieldcourses04/PapersMarineEcologyArticles/Th
eChemistryoftheOceansan.html
1. http://jrscience.wcp.muohio.edu/fieldcourses04/PapersMarineEcologyArticles/Th
eChemistryoftheOceansan.html
2. http://www.whoi.edu/main/news-releases/2007?tid=3622&cid=31286
Attachments:
Lesson Power points:
 Causes and Effects of Acid Rain and Ocean Acidification-11-12 graders
 Causes and Effects of Acid Rain and Ocean Acidification-six graders
Worksheets:
 Handout for six graders
 Handout for 11-12 graders
List CA Science Standards addressed:
 Students know matter is transferred over time from one organism to others in the
food web and between organisms and the physical environment.
 Construct appropriate graphs from data and develop qualitative statements about
the relationships between variables.
Environmental Science AP is not under CA Science standards but the following ones applied
for chemistry classes:
 Students know the observable properties of acids, bases, and salt solutions.



Students know acids are hydrogen-ion-donating and bases are hydrogen-ion-accepting
substances.
Students know how to use the pH scale to characterize acid and base solutions.
Students know how to calculate pH from the hydrogen-ion concentration. g.* Students
know buffers stabilize pH in acid–base reactions.