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Effect of Dissolved Carbon Dioxide Essay


((Carbon Dioxide is a greenhouse gas. It is everywhere ranging from our bodies to the atmosphere. Carbon dioxide is produced in living organisms as a result of cellular respiration (glucose + oxygen –>carbon dioxide + water + energy). It occurs in high concentrations in the tissues in our body. It then diffuses in the circulatory system where it may be carried in our blood))3. When this blood combines with water and then dissolves, Carbonic acid (hydrogen carbonate ions + hydrogen ions). are formed in the red blood cells which are then carried in the plasma. ((CO2 + H2O –> H2CO3))1. This dissolved carbon dioxide can easily change the pH of water. This carbonic acid is toxic to cells and therefore, whenever carbon dioxide is produced, the body tries to get rid of it before chemical activities are disturbed.

pH is a measurement of how acidic or basic a solution is. Water with pH lower than 7 is considered acidic and higher than 7 is known as basic. The safe levels of pH in drinking water is 6.5 – 8.5. Pure water has a pH of 7 which means there is an equilibrium of positive hydrogen ions and negative hydroxide ions. ((When the pH of water is below 6.5, the water is soft and corrosive. This type of water can damage metal pipes and when used, it can stain clothes, have a sour taste and damage sinks. Water with a Ph greater than 8.5 is considered hard.

This water does not pose a health risk, but can stain dishes and utensils))4. When Ph of water is low there can be many consequences and effects. ((Even a moderate decrease in pH of water could affect the fish egg hatching success; irritate fish and worst of all, damage membranes. Water with a pH below 4 or higher than 10 is deadly. It will most likely kill majority of sea creatures. Amphibians are at risk when the pH of water is low. If the pH of water is low, heavy metals will dissolve more readily which will make them even more toxic. When pH is high, ammonium in water is changed to toxic ammonia.)) 2


The dissolved Carbon Dioxide will cause the pH of water to decrease.

Risk Assessment:

While conducting this experiment a few safety precautions must be taken in order to prevent any damage to equipment or injuries. Also anything that poses a danger must be dealt with immediately. Some of the hazards and dangers of conducting this experiment and how to prevent them include:

Beakers are made of glass and are dangerous if broken. In order to prevent them breaking, they must be handled with outmost care.

If the water in the beakers is spilt, this will pose a danger as you can slip and injure yourself. Therefore the water must be handled with care and safety precautions must be taken.


1- To plan, design, choose equipment and perform a first-hand investigation to demonstrate the effect of varying Carbon Dioxide on the pH of water.

2- To test the hypothesis that dissolved Carbon Dioxide will cause the pH of water to decrease.


After conducting the experiment it was observed that my hypothesis was answered in the sense that adding dissolved Carbon Dioxide to water will cause its pH to decrease, therefore making it acidic. It was also observed that the more time spent exhaling through a straw into the water, the lower the pH. Choosing the correct method was quite a challenge for me, as there were many ways in which this experiment could’ve been conducted. After researching the different methods, I chose to go with exhaling Carbon Dioxide through a straw since It was the least time consuming. I also chose to measure the pH of the water with pH probe. I chose the pH probe because it has been proved that it is a very accurate device which has been used at an industrial scale.

After looking at the results I obtained, it can be concluded that Carbon Dioxide has a huge impact on water as the water’s pH decreases rapidly. Also, after comparing the results of my experiment to others, it seems that in all experiments carbon dioxide lowers the pH, which once again proves the
point that Carbon Dioxide does indeed lower the pH of water. This point is evident in all 3 trials conducted. However, there was a slight difference in the results, since many used distilled water, whereas I used tap water for my experiment.

A famous saying is that everything happens for a reason. There goes the same saying for Carbon Dioxide lowering the pH of water. When Carbon Dioxide is added to water, Carbonic acid is formed which consists of Hydrogen Carbonate ions and Hydrogen ions. The Hydrogen Carbonate is very toxic. The Hydrogen ions are the ones responsible for lowering the pH of water, therefore making it acidic.

All experiments are conducted either as a group or as an individual. Both these conditions have their advantages and disadvantages. This experiment was conducted individually. Many people would prefer conducting this experiment individually for a few reasons. Firstly, it would be hard to decide on a specific procedure to follow as group members would have varying opinions. Also, individually there will be no arguments as to how to do a specific thing (eg. How to produce CO2). However there can be disadvantages to conducting it individually. One of these is that there is nobody to give you a hand leaving you responsible for everything (eg. Blowing into water and observing the pH probe at the same time). Also if something was to go wrong, there is nobody to take over and continue which would affect the results dramatically.

It has been proven that dissolved Carbon Dioxide in the plasma causes a decrease in the pH of blood in mammals. This is also evident in this experiment. The more Carbon Dioxide in the blood the lower the pH goes as a result of increasing carbonic acid in the blood. The Carbonic acid formed is toxic to cells and therefore might damage or kill the cell. ((CO2 + H2O –> H2CO3. After that the carbonic acid reacts in the water to form hydronium ion (H3O) and the bicarbonate ion (HCO3). H2CO3 + H2O –> HCO3- + H3O+. The carbonic acid may neutralize hydroxide ions which increase pH, and bicarbonate ion can neutralize hydrogen ions which decrease the pH.

When carbon dioxide concentration increase or decrease, this can affect the equilibrium of the carbonate buffer which could be life threatening))1. Carbon Dioxide can also damage living tissue which will again affect metabolic efficiency. There are consequences of pH levels that are too low. Enzymes in our body will not function properly unless under optimum pH which in this case is 7.4. This in consequence will affect metabolic activity. As the pH goes too low or too high, the enzymes will begin to denature and eventually will stop working causing cells to die. These are the reasons why mammals need to get rid of Carbon Dioxide.

The method used in this experiment was just one of many. The method was quite effective in the sense that valid results were obtained. However there are many ways that could have made the results much more accurate. A data logger wasn’t available which could have been used to help transfer results straight to the computer saving time. Also, distilled water wasn’t available which would have been much more effective and since tap water results may be affected due to different chemicals, nutrients etc. Also instead of using a straw to exhale Carbon Dioxide, I could have produced pure Carbon Dioxide using one of many methods. Also the equipment that was used may have affected the results due to germs and bacteria that may have been on the equipment. If I was to make any changes, they would be using distilled water, producing pure Carbon Dioxide, using 3 different straws and using specific scientific equipment in order to carry out this experiment.


After conducting this experiment it has been demonstrated that varying Carbon Dioxide causes a decrease in the pH of water and that the more Carbon Dioxide dissolved in water, the lower the pH. This was evident in all three trials. This observation also supports my hypothesis (first page) perfectly.

Bibliography and Acknowledgements:

cati ons/publication/NR_WQ_2005-19.pdf+effects+of+low+pH+water&hl=en&ct=clnk&cd=1

Biology 2nd edition Practical Manual 2007 Heinemann Inc.


Kerri Humphreys, Surfing Biology, Maintaining a Balance revised edition

Biology 2nd edition 2007 Heinemann Inc.


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