Fires, Floods, and Droughts: Impacts of Climate Change in the U.S.

Classroom Activities

This unit will be nine class periods in length, where each class period is 90 minutes. Although it is written as a chemistry unit, sections of this unit can be adapted for use in physical science, biology, ecology, environmental science, or elementary school science classrooms.

Climate Change Impacts (1 class period)

As an introduction to this unit, I will show part of a short documentary in order to lead the students into a discussion about climate change impacts on the world and in different regions of the United States. Answering questions throughout the video will allow them to consider the wide scope and importance of this topic. I will also have the students complete a “jigsaw” reading activity where each group member reads a short selection of the 2018 NCA Climate Report, then has a chance to discuss what they’ve read as a group.

Hydrocarbons and the Combustion of Fuels (1 class period)

For this section of the unit, I will begin with a demonstration of the combustion of a candle. I will ask the students to consider which elements or compounds are required for the chemical reaction to take place and which elements or compounds are produced as a result. We will review the general chemical equation for a combustion reaction, and then they will be able to practice balancing this type of reaction. I will also have the students calculate the mass of CO₂ produced by the combustion of a hydrocarbon to show that for every gram of hydrocarbon burned, more than one gram of CO₂ will be produced. In groups, I will then have students look at data for carbon dioxide levels from before the Industrial Revolution until today so that they can try and observe any patterns or trends. I will have the students look at some data displaying global average temperatures for that same time period to see what patterns or trends they are able to find. This will help them make the connection between the two variables, CO₂ production and global temperature. I will have the students complete an additional short reading for homework.

Ocean Acidification: an Impact of Climate Change (3 class periods)

For the section of the unit about the chemistry of ocean acidification, two experiments or demonstrations can be conducted to show the relationship between CO₂ and water pH. The first experiment involves adding phenolphthalein indicator to a slightly basic solution in a beaker with a stir bar and placing it in a vase that can be covered. A small candle is then added into the vase and lit. After lighting the candle, the vase is then covered. As the candle undergoes combustion, it will produce CO₂, and as it produces CO₂, some of the gas will dissolve in the water as it stirs. This will cause the indicator to change the solution color from pink to colorless, indicating that the solution is changing from basic to more acidic.

An additional experiment involves adding some bromothymol blue indicator to a beaker with some water. A student then blows bubbles into the beaker through a straw and can watch as the solution changes from blue to yellow, indicating a change from neutral to acidic. I will provide the students with guided notes about the chemical equations in this part of the unit. I will demonstrate a simplified reaction of carbon dioxide (CO₂) and water (H₂O) to produce bicarbonate ions (HCO₃^-) and hydronium ions (H₃O⁺).

For the chemistry of acids, bases, and pH section of the unit, I plan to begin with a virtual demonstration through PhET (University of Colorado Boulder) about the different pH values of household and other common substances and allow the students to synthesize general trends about acidic and basic substances.²¹ Additionally, I may also have the students complete a laboratory activity about pH similar to the PhET activity. A broad range of substances can be brought in to illustrate different pH values of household substances. Tap water, sparkling water, coffee, antacid, orange juice, vinegar, cocoa powder, ammonia, and bleach can be used to achieve a wide range of different pH values using pH test strips or pH probes.

I plan to have an additional activity to build student knowledge about indicators. Students can extract pigments from hibiscus and tea leaves and use these pigments to create indicator solutions that show a range of colors when exposed to solutions with different pH values. Indicators are substances that naturally change color within different pH ranges. This can be connected to how pH paper works.

After allowing them to engage with the differences between acids and bases, I am planning to implement guided notes about these topics and draw connections between pH and molarity, which they will recognize from a previous unit. After modeling the use of the pH equation, I will enable the students to practice in groups and on their own in order to become more familiar with basic pH calculations and begin to understand them from the chemical context of the concentration of H₃O⁺. This discussion of basic pH principles will lead into the concept of ocean pH and how it can vary depending on the chemical composition of the water. The students can calculate and compare the pH values of a solution with more H₃O⁺ and a solution with less H₃O⁺ ions. This will allow them to draw the mathematical connection to why additional dissolved CO₂ in the ocean will reduce the pH. 

I will continue this unit with guided notes about carbonate ions and their importance for certain marine organisms. I will present the updated reaction between CO₂, H₂O, and CO₃^-2 to produce HCO₃^-, and explain how this reaction occurs in the presence of carbonate ions. Students will have the opportunity to look at aragonite saturation data and begin to see relationships between aragonite saturation and dissolved CO₂ in ocean water.

Biodiversity Loss of Marine Organisms (2 class periods)

For this section of the unit, I plan to begin with the laboratory experiment related to marine organism shells. I will have the students create a solution that is chemically similar to seawater and have them split it into 3 different beakers. One beaker will have a pH close to that of the ocean (8), one will have a pH lower (6), and the third will have a pH even lower (4). The students will observe the effects of more acidic water on the shells. I will then have them discuss in groups why ocean acidification could have a negative impact on marine organisms. This will be the basis of this section of the unit. Additionally, we will review notes related to this phenomenon and watch some short videos to illustrate the effects of ocean acidification on marine organisms such as pteropods, shellfish, and coral. This will set the stage for the next section of the unit.

We will begin the biodiversity section of this unit with an ecology-based food web activity so that the students can see the importance of smaller organisms such as pteropods that are closer to the bottom of the food chain. When given a food web, students will complete food pathways that involve pteropods. Then, they can remove the pteropods to see how many other organisms will be affected. As fish and other marine organisms can no longer rely on pteropods for their primary food source, their numbers will diminish. Since many of these organisms are toward the base of the marine food chain, their reduction will cause the reduction of other species that utilize them as food sources.

Additionally, I will draw the students into a conversation about coral reefs and the biodiversity that they can support within their ecosystems. We will watch some pieces of the documentary Chasing Coral about coral reefs so that students can experience the rich marine life in those regions and learn more about climate change impacts specifically on coral reef ecosystems.

Other Climate Change Impacts (1 class period)

This section of the unit will focus on the effects of eutrophication and hypoxia on certain marine organisms in estuaries. This will create a good opportunity for students to recall the process of photosynthesis. I will refresh them about this with an online interactive activity. After this activity, the students will work in groups to brainstorm a multi-step mechanism for why more sediments and nutrients being added to water as well as greater CO₂ concentrations would cause algae populations to increase, estuary hypoxia to occur, and marine organisms that are not highly mobile to be negatively affected.

I will also include guided notes for discussion about surface ocean temperatures and their relationship to deoxygenation in oceans. Students will be able to make connections between deoxygenation and hypoxia due to their similar effects on marine organisms. Another activity in this section of the unit will be a brief student-led research investigation about the different marine species that live in the Chesapeake Bay and how they would be impacted by increasing water temperatures.

Data Retrieval and Analysis (1 class period)

For the section of the unit focused on data analysis, I will frame it through the lens of the EPA Bermuda data set. This data set will be downloaded in its entirety from the EPA website. Once downloaded as a .csv file, it can be opened with any data software, such as Microsoft Excel or Google Sheets. Once the data is available in the software, it can be turned into three different graphs as shown in the Unit Content section, pCO₂ data acquired from 1983-2016, pH data acquired from 1983-2016, and pCO₂ vs. pH data acquired from 1983-2016. This is a great opportunity for the students to be able to consider different features within this graphing software such as titling the graph, labeling axes with units, setting the minimum and maximum values for each axis, and creating a trendline. Using a trendline and the equation of a line, students can also practice estimating pH and PCO₂ values given the other. This is a good exploration for students to learn about graphing and observing general trends in data. This also offers a great opportunity for students to practice their skills with graph analysis by making a claim based on the graphed data. 

I am hoping to show my students how easy it is to access countless data for free from government sources. I am also hoping to show the value of looking at data closely to see if there are any recognizable patterns or features of interest. More specifically as it relates to ocean acidification, I would like students to become well versed in some of the evidence for long term climate change effects and even more so the evidence of climate change impacting their local environments.