Lesson Plan: Buffers, Buffer Action and Ocean Acidification

by TROP ICSU

As a high school or undergraduate Chemistry, 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).

 

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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About Lesson Plan

Grade Level High school, Undergraduate
Discipline
  • Chemistry
  • Environmental Sciences
  • Earth Sciences
Topic(s) in Discipline
  • Buffers, Buffer Action
  • pH Level
  • Buffer Capacity
  • Buffer Range
  • Acidification
  • Le Chatelier’s Principle
Climate Topic
  • Climate and the Hydrosphere
  • Climate and the Atmosphere
  • Climate and the Biosphere
Location Global
Language(s) English
Access Online
Approximate
Time Required		 30-40 min

Questions

Use this lesson plan to help your students find answers to:.

  1. What are buffers? Explain buffer action.
  2. Describe carbonate buffering in the ocean.
  3. What is ocean acidification?
  4. 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?

 

Contents

Reading
(~10 min)		 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

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
  1. 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.

 

  1. 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.

 

  1. Discuss other examples of buffers in daily life, e.g., the buffering action of blood.

Go to the reading
2 Play a video micro-lecture to explain the buffer chemistry of oceans
  1. Use the video micro-lecture “Ocean Buffer Chemistry” by Prof. David Archer, University of Chicago, to describe carbonate buffering in the ocean.

 

  1. 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).

 

  1. 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).

 

  1. 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.

 

Go to the video micro-lecture
2 Play a video micro-lecture to explain the buffer chemistry of oceans
  1. Open the applet “Surface Ocean pH Levels” from The King’s Centre for Visualization in Science (KCVS), available at http://www.kcvs.ca/site/projects/JS_files/OceanAcidification/oceanAcid.html.

 

  1. Select the “Resources” tab to read the background that provides a detailed explanation of the relationship between atmospheric CO2 and ocean pH values.

 

  1. Click on “Help” 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 left hand side 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 “Options” to view the different emission scenarios (Special Report on Emission Scenarios (SRES) projections) that can be selected. Select different SRES projection options and visualize the corresponding predicted ocean pH value on the pH indicator strip or on the aforementioned graphs.

Note:  Detailed information about SRES projections

 

  1. Finally, discuss the implications of the predicted pH value of oceans for different emission scenarios and the possible impacts on the Earth’s biosphere.

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