As a high school or undergraduateChemistry, Environmental Sciences, or Earth Sciences teacher, you can use this set of computer-based tools to teach about buffers, how buffers work (buffer action), ocean carbonate buffering, and ocean acidification due to higher levels of atmospheric carbon dioxide (CO2).
Video Tutorial : How to use this Lesson Plan
Please note, the first 3 min 52 sec of the video introduce how to use TROP ICSU resources followed by description of this Lesson Plan.
This lesson plan introduces the topic of buffers and describes carbonate buffering in the ocean when atmospheric CO2 dissolves in seawater. The buffering capacity of the ocean is, however, limited, and therefore, higher concentrations of dissolved CO2 can lead to ocean acidification. Students will use a computer-based activity/model to explore how higher atmospheric CO2 levels (resulting in an increase in dissolved CO2) can lead to ocean acidification. Thus, the use of this lesson plan allows you to integrate the teaching of a climate science topic with a core topic in Chemistry, Environmental Sciences, or Earth Sciences.
Lesson plan based on an idea submitted by Dr. Pragya Gahlot, Sri Venkateswara College (University of Delhi), India.
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This reading introduces the topic of buffers and explains the chemistry of buffer action in solution through examples. Go to the reading
Video micro-lecture (7 min)
This video micro-lecture explains carbonate buffering in the ocean. It also briefly discusses the change in the chemical composition of the ocean caused by a higher concentration of dissolved CO2, and the resulting effect on ocean biota. Go to the video
Visualisation
(~10-20 min)
This visualization allows students to explore changes in the pH levels of oceans for different levels of atmospheric CO2, including the CO2 levels corresponding to various emission scenarios (as published by the Intergovernmental Panel on Climate Change (IPCC)). Go to the Visualisation
Questions
Use this lesson plan to help your students find answers to:.
What are buffers? Explain buffer action.
Describe carbonate buffering in the ocean.
What is ocean acidification?
Discuss the possible global impact of higher levels of atmospheric CO2 on the pH of oceans.Describe carbonate buffering in the ocean.What is ocean acidification?
Step-by-Step User Guide
Questions/Assignments
Learning Outcomes
Additional Resources
Credits
Here is a step-by-step guide to using this lesson plan in the classroom/laboratory. We have suggested these steps as a possible plan of action. You may customize the lesson plan according to your preferences and requirements.
1
Introduce the topic with the help of a reading
Introduce the topic of buffers. Use the reading “How Does A Buffer Maintain pH?” by LibreTextsTM to explain buffer action and the maintenance of pH in a buffer solution.
Explain the term buffer capacity, buffer range, and the pH equation of a given buffer. Use examples (1 and 2) given in the text to calculate changes in the pH values when a weak acid or base is added to a buffer solution.
Discuss other examples of buffers in daily life, e.g., the buffering action of blood.
Play a video micro-lecture to explain the buffer chemistry of oceans
Use the video micro-lecture “Ocean Buffer Chemistry” by Prof. David Archer, University of Chicago, to describe carbonate buffering in the ocean.
Discuss how oceans behave as carbon sinks by absorbing atmospheric CO2, and the maintenance of ocean pH levels owing to the buffering capacity of seawater. Further, use the video to explain the buffering range of oceans and the chemical implications of a higher concentration of dissolved CO2 (due to increased levels of atmospheric CO2).
Explain how high levels of atmospheric CO2 could result in an excess of free hydrogen (H+) ions, thus potentially changing the pH values of seawater (acidification).
Further, use the video micro-lecture to illustrate Le Chatelier’s Principle—explain how increased CO2 concentration in seawater sequesters more carbonate (CO32-) ions to keep the system in equilibrium. In conclusion, explain how ocean biota may be affected in the absence of freely available carbonate (CO32-) ions.
Select the “Background” tab to read the background that provides a detailed explanation of the relationship between atmospheric CO2 and ocean pH values.
Click on “Instructions” to read the instructions to run the applet.
- Run the simulation to enable students to visualize the global pH value (as indicated on the pH indicator strip) of oceans for a given concentration of atmospheric CO2. Students can vary the atmospheric CO2 levels by using the slider at the bottom to observe the corresponding changes in the pH value of the oceans.
- Click the tab “Show Graph” to observe the graphs for concentrations of various species of carbonate ions in (i) a closed system and (ii) an open ocean; and the graph depicting the pH value of oceans for various atmospheric CO2 concentrations.
- Go to the tab “2100 CE Projections” to view the different emission scenarios (RCP Projections) that can be selected. Select different RCP projection options and visualize the corresponding predicted ocean pH value on the pH indicator strip or on the aforementioned graphs.
Note: Detailed information about RCP projections is available in the same tab. Detailed information about SRES projections is available here.
Finally, discuss the implications of the predicted pH value of oceans for different emission scenarios and the possible impacts on the Earth’s biosphere.
Use the tools and the concepts learned so far to discuss and determine answers to the following questions:
What are buffers? Explain buffer action.
Describe carbonate buffering in the ocean.
What is ocean acidification?
Discuss the possible global impact of higher levels of atmospheric CO2 on the pH of oceans.
The tools in this lesson plan will enable students to:
define buffers and describe buffer action
describe the terms buffer capacity and buffer range
explain the buffering action of seawater
explain ocean acidification and discuss its possible impact on the biosphere
If you or your students would like to explore the topic further, these additional resources will be useful.
1
Laboratory Activity
(High School)
A laboratory activity— “The Buffer Zone” by Stefani Hines, University of New Mexico, published in the Environmental Health Perspectives (EHP) Science Education Program—that allows students to explore the buffering ability of seawater and discuss how this buffer action is affected by increasing levels of atmospheric CO2 and increasing global temperatures.
An animated video, “Demystifying ocean acidification and biodiversity impacts” from the California Academy of Sciences, to learn about ocean acidification and its impacts on the biodiversity of the planet.
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