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Defines pH indicators and explains how they function.

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Recall: Indicators are chemical compounds that turn specific colors when they come in contact with acids or bases

Credit: http://commons.wikimedia.org/wiki/File:701_Pool_des_Hotels_Ciaudad_Laurel_in_Cala_Millor_-_Wasserballspieler.jpg
Source: user: Usien
License: CC BY-NC 3.0

What's your favorite pool activity? [Figure1]

Have you ever swum in a pool that stung your eyes? Have you ever left a pool with extremely itchy, dry skin?  These are symptoms of poorly treated pH levels in pool water and could most likely have been avoided! Pool water is most comfortable to the human body at a pH as neutral -- or close to a pH of 7 -- as possible. In order to maintain favorable swimming conditions, pool water is tested with pH indicators regularly. If the pH of the water is too high or too low, additives to the water can help to increase or decrease the pH. By swimming in a pool where the pH of the water is too acidic or alkaline, you are risking more than just comfort, you are risking your health!

Creative Applications

1. You test your pool water with the indicator methyl orange which turns orange-yellow when in contact with pool water. Give an estimate of your pool’s pH. Is this too high or too low?

2. Refer to the question above. What side effects could this pH level have if you were to swim in a pool filled with this water?

3. You add additives to the water in question 1 and now the water turns blue when the indicator bromothymol blue (BTB) is added. Give an estimate of your pool’s new pH. Is this too high or too low?

4. One indicator reads pH levels in the range of 7.2- 10.4 and another reads pH levels in the range of 5.6- 8.3. Which indicator is most helpful for indicating pH levels for pool maintenance?

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  1. [1]^ Credit: http://commons.wikimedia.org/wiki/File:701_Pool_des_Hotels_Ciaudad_Laurel_in_Cala_Millor_-_Wasserballspieler.jpg; Source: user: Usien; License: CC BY-NC 3.0

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