Water Planet Challenge

Electrically Speaking: Carbonated Oceans! - High School

Introduction

Students often have preconceptions about how their actions can and do effect the environment. This lesson is focused on how the use of fossil fuels to produce electricity impacts the atmosphere and in turn the waters of the Earth, in particular the oceans. Students will explore the interaction of temperature and carbon dioxide on water chemistry. The questions are how has and does the ocean absorb and reemit carbon dioxide emissions from the air, and how does the incorporation of CO2 into the ocean change the pH of ocean water.

Objectives

• Describe how everyday human activities produce pollutants that can be measured.
• Measurements of pollutants are used to determine the nature of the affect they have on the planet, its resources, and health of organisms on the planet.
• Students should be able to explain how the burning of fossil fuels leads to the acidification and warming of the oceans.

Materials

• Computer and websites
• Library and/or classroom resources
• Science journal
• New paper or plastic cups or very clean beakers
• Tap water
• Distilled water
• Salt water approximately 35ppm
• Spring water with minerals
• Carbonated Seltzer water
• pH paper strips or a pH meter
• refrigerator

Vocabulary

• Global warming – refers to an average increase in the Earth's temperature over time
• Climate change – a result of the overall average increase in the Earth’s temperature. This term encompasses all changes to the Earth’s climate, ecosystems, human health and society.
• Anthropomorphic carbon- carbon emitted to the atmosphere due to the activities of man and closely linked to current changes in the climate..
• Environment – the habitats surrounding an area
• Acidification – ongoing decrease in the pH of the Earth's oceans
• CO2– carbon dioxide, the primary greenhouse gas Carbonization
• Carbon cycle - the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere, and atmosphere of the Earth.
• Atmosphere – the layer of gases surrounding the Earth
• Hydrosphere – the waters of the Earth
• Biosphere – all regions of the Earth environs that house life.
• Solubility – is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution
• Saturation – saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of it will appear as a precipitate
• Equilibrium – is the property of a system, either open or closed, that regulates its internal environment and tends to maintain a stable, constant condition
• Open system – a system where matter or energy can flow into and/or out of the system
• Closed system – where energy can enter or leave but matter may not enter or leave
• Halothermal circulation – the great conveyor belt of circulation that links all oceans. Warm water in the north Atlantic evaporates and cools the surface water. This cooler and denser water sinks to the sea floor and drives the entire multi-ocean circulation. This stream of water also carries the carbon dioxide that is dissolved into the cold polar water during winter storms.

Teacher Background

Since the beginning of the industrial revolution the burning of fossil fuels for human activities has increased the release of carbon dioxide (CO2) and other heat trapping gasses into the atmosphere. The result has been warming of the atmosphere and ocean, plus production of acid in ocean water. The atmospheric concentration of CO2 is now higher than experienced on Earth for at least the last 800,000 years and probably over 20 million years, and is expected to continue to rise at an increasing rate. This can lead to significant temperature increases in the atmosphere and oceans in the coming decades.

The oceans have absorbed approximately 525 billion tons of carbon dioxide from the atmosphere, or about one third of the carbon emissions released. How does this happen? The ocean is an open system interacting with the atmosphere through wave action and precipitation; approximately 30% of the atmospheric CO2 dissolves into the ocean and forms carbonic acid (CO2 +H2O ? H2Co3). This absorption has benefited humankind by significantly reducing the greenhouse gas levels in the atmosphere and minimizing some of the impacts of global warming. However, the ocean's uptake of carbon dioxide is having negative impacts on the chemistry and biology of the oceans. Surveys and modeling studies have revealed that the chemical changes in seawater are lowering seawater pH or making it more acidic. The pH of ocean surface waters has already decreased by about 0.1 units from an average of about 8.21 to 8.10 since the beginning of the industrial revolution. Estimates of future atmospheric and oceanic carbon dioxide concentrations suggest that by 2050 atmospheric carbon dioxide levels could reach more than 500 ppm, and near the end of the century they could be over 800 ppm. This would result in an additional surface water pH decrease of approximately 0.3 pH units by 2100.

The addition of anthropomorphic carbon dioxide caused by our burning of fossil fuels has intensified the greenhouse effect shown in the following diagram. The Earth is in radiative balance, the sun provides radiant energy to the Earth in turn the Earth radiates or reflects radiation out into space at an equal rate. There is evidence that the build up of heat trapping gasses such as CO2 has increased the temperature of the Earth’s radiative balance during the last 100 years.

http://upload.wikimedia.org/wikipedia/commons/thumb/5/58/Greenhouse_Effect.svg/750px-Greenhouse_Effect.svg.png http://kids.earth.nasa.gov/seawifs/images/carboncycle.gif

The increase in the overall temperature of the atmosphere and ocean has an impact on organisms in the ocean in conjunction with the acidification of the ocean. The effects of this decreasing pH can have multiple effects on life in the ocean. True the algae and sea plants may benefit from increased CO2. using it to photosynthesis. The animal life can be affected several different ways, the creation of carbonic acid is dissolving the shells of shell fish and corals that are made of calcium carbonate. The acid is also reducing the available molecules these animals use to build their shells. Studies are also being conducted concerning the effect of lower pH on the reproduction rates of sea urchins, oysters and corals. In the event that these organisms die out it will disrupt the marine food chains and human fisheries.

Adapted from NOAA

http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

http://www.noaa.gov/video/administrator/acidification/

http://coralreefwatch.noaa.gov/satellite/oa/description/oaps_intro_oa.html

http://www.nrdc.org/oceans/acidification/aboutthefilm.asp (21 minutes)

Suggested sidebars are the possible answers to the lab about water pH values.
http://www.phconnection.com/Bottled_Water_pH_List.html

Information on the pH of different types of water:

The generally accepted pH level of pure water is 7.The generally accepted pH level in a basic saltwater system is between 7.6 and 8.4,. Chemically speaking, salt is a base compound, falling in the center of the acid-alkaline spectrum. If the water had a very low pH, making it very acidic, the salt would increase the pH toward the center of the spectrum.

The pH of mineral water is often thought to have a pH value of 7 (neutral). That is not the case. Most mineral waters are slightly acidic in value, ranging from 5.7 to 7. The value varies according to the mineral content of the water, and the type of earth from which the water is drawn in turn affects this. Water which was percolated through a hard rock, like granite will have a higher mineral content than distilled water, and will thus tend to be more acidic.

Seltzer water, or carbonated water, usually has a pH level of 2.8 to 3.0.

Engage

The teacher will provide each student with two different samples of soda, (they are not to tell them the difference) one is fresh and carbonated the other has been sitting out and is “flat” or the carbon dioxide has bubbled out of it. In order to ensure a fair test, prepare the “flat” soda the day before so it can be refrigerated to the same temperature as the carbonated pop. Warm soda will become flat quickly.
Students will taste each sample and describe what they observe. Students should consider smell, taste, color, and texture (bubbles no bubbles).

The teacher will ask students to follow the procedures below, discuss with their partner/s and answer the questions.

1. What were the differences you and others in your group observed between a carbonated soda and that same soda when it goes flat? Answers will vary: no bubbles, tastes sweeter, color variations.

2. Use the pH meter or pH paper and test the flat soda and the carbonated soda. Answers will vary but the carbonated soda should be more acidic or a lower pH.

3. What is the chemical difference between the two samples? The carbonated soda is more acidic.

4. What seems to be the affect of carbonation to the soda? It makes the soda more acidic and taste less sweet.

Explore

Testable Question
How does dissolving certain chemicals (salt, CO2, and certain minerals) in water affect the pH?

Materials

• New paper or plastic containers or very clean beakers
• Tap water
• Distilled water
• Salt water approximately 35 ppm
• Spring water with minerals (different spring waters have different minerals in different amounts)
• Carbonated Seltzer water
• pH paper strips or a pH meter
• refrigerator

Procedures

1. Chill the 5 types of water.
2. Label each container with the type of water sample.
3. Pour 50 ml of the correct sample of water into each container.
4. Using a clean strip of pH paper (or the pH meter) for each container, test each water sample and record the value in a chart.
5. Now repeat the experiment using room temperature waters.
6. Answer the analysis questions.

Analysis

Use data from your experiments to answer the following questions:

1. Using data from the experiment describe the effect the addition of salt had on the pH of the water.
Answers may vary but salt water is usually a pH of about 7.6-8.4.

2. Using data from the experiment describe the effect the addition of CO2 had on the pH of the water.
Answer may vary but carbonation should decrease the pH to as low as 3.0.

3. Using data from the experiment describe the effect of increasing the temperature on the pH of the different water samples? Increasing temperatures seem to speed the loss of CO2 into the water, resulting in a increase of the pH. (NOTE: This may be counter intuitive to the students as they try to apply it to their understanding of global warming and the increased acidification of the oceans both due to the increase of CO2 in the atmosphere. This will be resolved later in the lesson. Though the ocean is becoming more acidic due to the absorption of atmospheric CO2, the warming of the oceans due to global warming actually helps to remove the CO2 from the oceans. Currently, the rate of absorption is still greater than the rate of reemission to the atmosphere, so the net gain for the oceans is to continue to become more acidic. Absorption happens in the polar seas and reemission happens in the tropics.)

4. Which of the chemicals tested seem to cause the largest change in pH to make it acidic?
Carbonation seems to make the water more acidic.

5. What do you think will happen when you combine salt water with carbonation? Students may think they cancel each other out but in fact they do not because the ocean is not getting saltier but it is absorbing more carbon dioxide yearly.

Explain (with further research)

Show this short video to students about CO2 and the oceans ask them to discuss and answer the following questions.

http://www.pmel.noaa.gov/co2/OA/A_Sea_Change_Excerpt.mov

1. How would these chemicals (salt, CO2, other minerals) get into the ocean? Acid rain, wave action and splashing, from the rivers and streams, which carry air bubbles.

2. What happens chemically to the carbon dioxide when it becomes incorporated into the ocean water?
CO2 + H2O = H2CO3
Carbon Dioxide plus Water produces carbonic acid

3. Is there a relationship between temperature and pH in ocean water? If so what is it.
Cold water dissolves and holds more CO2 and therefore is more acidic than warm water. The warm samples of carbonated water had a higher pH, or less acid than the cold samples.

4. Explain how a lower pH or more acidic pH may affect the ecology of the ocean. Acid burns the skin and parts of animals and plants exposed to it. When this happens some animals and plants will die. Then there will be less food for other animals. Students will explore the effect of temperature and acid on the life forms in the next lesson.

5. Think about what you know about marine animals. Which do you think maybe most affected by acidification of oceans and why you think that? Answers will vary the answer is based on what the students know about marine ecosystems. The next lesson will give the students an opportunity to expand their thinking with research into the effect of acidification and warming on life in the sea.

6. Examine the images below. Is there a relationship between temperature and pH in ocean water? If so what is it? Yes, in tropical areas where the temperature of the ocean is warmer the acid content is lower than at the poles.

This series of maps shows the predicted acidification of the ocean if carbon dioxide emissions do not change.

7. Explain what is happening to the oceans as the carbon cycle interacts with the geochemistry of oceans. Use the evidence you have collected from the first 3 activities. Use the diagram below and links below to further inform you thinking before writing your response.
Answers may vary but student should notice the acidification is starting near the poles in cold temperature waters first, then spreading from there. Thinking back to how much electricity they use and the carbon dioxide emissions from producing the electricity make a connection between the human use of electricity to the predicted acidification of the ocean. In this activity they learned that those emissions are being incorporated into the ocean water causing the ocean to become more acidic. The cold soda held more carbonation and was more acidic than the warm soda. Over time if the oceans warm to the point of losing the halothermal circulation, we can expect the oceans that have been great storehouses of our anthropomorphic carbon, to actually reemit carbon dioxide to the atmosphere which could lead to more rapid global warming.

http://oceanservice.noaa.gov/facts/conveyor.html

Additional videos and other web resources to explain:

http://www.climatewatch.noaa.gov/2010/videos/origin-impacts-ocean-acidification
http://www.climatewatch.noaa.gov/2010/images/ocean-acidification-today-and-in-the-future

Measuring and monitoring the amounts of CO2 mixing in the oceans: http://www.oar.noaa.gov/research/2007/ocean_acidity.shtml

Explaining the chemical interactions of CO2 once it has entered the oceans:
http://coralreefwatch.noaa.gov/satellite/oa/description/oaps_intro_oa.html

Elaborate

The ocean is not the same salinity everywhere. Where large rivers feed into the ocean the ocean the water is less salty or where ice forms on the top of the water the water underneath is more salty. Salinity can increase or decrease in oceans due to local temperature regimes. The Mediterranean Sea is far saltier than the neighboring Atlantic ocean due to the high rate of evaporation that the region experiences. Likewise, during the winter at the poles as sea water freezes, the surrounding water becomes saltier as the ice that forms is nearly pure water.

Students could examine the effect of different salinities of ocean water on the pH and then determine where acidification may lead to more damage than other places.

Students could also think about and test which minerals may make ocean water more basic and counteract the affect of carbon dioxide.

Students could look at maps of acidification and try to determine why those portions of the ocean seem to be most affected. Are they near industrial areas? Is there a correlation to areas with high acid rain measurements?

National Standards

B. ESS Core Idea 4: Human activities are constrained by and, in turn, affect all other processes at Earth’s surface. [Human Interactions with Earth] Grade 9-12
Sub-question: How will global climate change affect humans?
Climate change, driven by both natural and human activities, has large consequences for all of Earth’s surface systems, including humans. Humans can take actions to reduce climate change and its impacts.
1. How might global climate change affect humans?
• As carbon dioxide levels in the atmosphere rise, ocean water becomes more acidic, threatening the survival of shell-building marine species and the food webs of which they are a part.
• Ecosystems will be disturbed by climate change; animals, plants, bacteria, and viruses are likely to migrate to new areas or become extinct.
• Geological records of past climates show that climate shifts can occur quite rapidly when certain positive-feedback “tipping points” are reached.
2. What can be done to reduce global climate change and its negative impacts?
• Measurements of greenhouse gas emissions and other factors that drive climate change are used in climate models to make predictions about climate change. These models aid in decision-making for individuals, institutions, communities, and governments.