Collaborators:
Katie Lowe, Serena Spencer, and Nicole Walker
Introduction / Problem:
At the beginning of this experiment a question was presented, Whether or not carbon dioxide affects the pH of the ocean. Normally the pH of the ocean is 8.2. However, According to National Geographic, Today, it is around 8.1, a drop of 0.1 pH units, due to a 25% increase in acidity over the past two centuries. This acidity is a result of all the alkalinity founded in Limestone. Limestone is a sedimentary rock formed by the compaction of fossilized coral, shells and bones. Components in Limestone consist of Calcium Carbonate and Dolomite. These substances react with water causing a release of hydroxide. As a result from the release of the hydroxide the pH will spike. Therefore buffering, a chemical that resist a change in acidity when an acid or base is added to it, or a substance that facilitates this resistance. Alkalinity is used to find out the capacity of water or any solution to neutralize or “buffer”. As of lately it has been reported that the worlds oceans have absorbed Calcium Carbonate, which then react poorly with the components in the ocean thus increasing the pH.
Hypothesis:
If carbon dioxide is added into the salt water, then the pH of the water will lower due to the addition of hydrogen-ions released by the dissolved carbon dioxide. If carbon dioxide is added to distilled water, then the pH of that solution will be enthrall compared to ocean water from the lack of salt. If calcium carbonate is added to salt water, then it will raise the pH due to the calcium carbonate reacting with the hydrogen-ions creating a "buffer".
Parts of Experiment:
- The Independent Variable is the Carbon Dioxide itself.
- The Dependent Variable is the pH of the solution presented by the addition of Carbon Dioxide.
- The Controlled Variables ranged from the amounts of Carbon Dioxide, straws, water in each test tube, universal indicator, and Calcium Carbonate.
Materials:
- Two test tubes
- Two Graduated Cylinders
- Distilled Water
- Salt Water
- Universal Indicator
- Straw
- Calcium Carbonate
Methods:
- Put 1 ml of universal indicator into 10 ml of ocean water, record the pH.
- Put 1 ml of universal indicator into 10 ml of distilled water, record the pH.
- Using a straw, slowly breathe into the test tubes, record the time it takes for the color to change.
- Add 1g of crushed Calcium Carbonate to each test tube, record the results.
Data: |
Analysis:The data table shows the recorded times for the pH to either increase or decrease with the addition of carbon dioxide and calcium carbonate. This data shows the ocean water to be originally 8 pH, although with the addition of carbon dioxide it has decreased to 6 pH. Comparatively the addition of carbon dioxide to distilled water; originally was 6 however, it had decreased significantly to 1. Distilled water had changed in 9.2 seconds, while ocean water took 3 minutes and 26 seconds to decrease. The difference between the solution was caused by a buffering agent found in ocean water, requiring a longer time to change pH than Distilled water. As recorded there was an increase to both solution with the addition of calcium carbonate. Each solution had also turned from a light color to a dull dark color. The calcium carbonate acted as a neutralizing agent therefore the spike to a more basic solution rather than acidic.
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Pictures:
Conclusion:
As concluded the data supports the hypothesis if carbon dioxide is added to water, then the pH of the water will be lowered. Likewise if calcium carbonate is added to salt water then it will raise the pH.
In this experiment the pH of the ocean water was originally 8, however once calcium carbonate was added, the pH had changed to 7. The difference of 1 point may have been due to the factor of a strong concentration of calcium carbonate added to a small portion of sea water. There was an obvious difference in the distilled water and ocean water's reaction towards carbon dioxide. Once carbon dioxide was added into both the distilled water had changed from the number 6 to the number 1 in 9.2 seconds. As well as the ocean water changing from the number 8 to the number 6 in 3 minutes and 26 seconds. This difference may have been caused due to the lack of buffering acquired in distilled water. Comparatively, the salt water has a higher buffering agent from the salt, producing a longer time to change pH.
Finally, an addition of calcium carbonate to each solution caused a rise. In 2.4 seconds the distilled water's pH had risen from 1 to 9. While it took 8 seconds for the ocean water's pH to increase from 6 to 7. The cause for the rise in distilled water is because the calcium carbonate had reacted with the previously added carbon dioxide driving up the pH. The reason for the cause of the ocean water's pH to increase is due to the calcium carbonate having a higher acid-neutralizing capacity than carbon dioxide.
In this experiment the pH of the ocean water was originally 8, however once calcium carbonate was added, the pH had changed to 7. The difference of 1 point may have been due to the factor of a strong concentration of calcium carbonate added to a small portion of sea water. There was an obvious difference in the distilled water and ocean water's reaction towards carbon dioxide. Once carbon dioxide was added into both the distilled water had changed from the number 6 to the number 1 in 9.2 seconds. As well as the ocean water changing from the number 8 to the number 6 in 3 minutes and 26 seconds. This difference may have been caused due to the lack of buffering acquired in distilled water. Comparatively, the salt water has a higher buffering agent from the salt, producing a longer time to change pH.
Finally, an addition of calcium carbonate to each solution caused a rise. In 2.4 seconds the distilled water's pH had risen from 1 to 9. While it took 8 seconds for the ocean water's pH to increase from 6 to 7. The cause for the rise in distilled water is because the calcium carbonate had reacted with the previously added carbon dioxide driving up the pH. The reason for the cause of the ocean water's pH to increase is due to the calcium carbonate having a higher acid-neutralizing capacity than carbon dioxide.
Citations:
"Alkalinity." Alkalinity. N.p., n.d. Web. 25 Jan. 2015.
"Ocean Acidification -- National Geographic." National Geographic. N.p., n.d. Web. 25 Jan. 2015.
"What Is Ocean Acidification?" What Is Ocean Acidification? N.p., n.d. Web. 25 Jan. 2015.
"Ocean Acidification -- National Geographic." National Geographic. N.p., n.d. Web. 25 Jan. 2015.
"What Is Ocean Acidification?" What Is Ocean Acidification? N.p., n.d. Web. 25 Jan. 2015.