Water+Safety+and+Quality


 * Research Question: ** Is water quality safe at Taipei American School?

Dissolved oxygen was measured using the Vernier Dissolved Oxygen probe. Chloride presence was qualitatively tested for according to precipitation formation. Calcium level was quantified by the height of soap bubbles produced. || The amount of source water used was kept constant through each experiment. The amount of time used before conducting measurements was also kept consistent between trials. ||
 * Type of Variable || Variable || Description / Explanation ||
 * Independent Variable || Water Sources || Water was obtained from seven different sources: tap water (from the 1st Floor Science bathroom), bottled water, distilled water, pond water (from the lower school pond), pool water, and dispenser water (from the water dispenser in front of the summer school activities office). ||
 * Dependent Variable || pH, dissolved oxygen, chloride presence, calcium level || pH was measured using the Vernier pH probe.
 * Control || Temperature, amount of source water, time || The temperature for all water was kept at 24.6°C.


 * Materials: **
 * Vernier pH probe
 * Vernier dissolved oxygen probe
 * Test tubes (7)
 * Beaker (5 x 100mL, 7 x 600mL)
 * Graduated cylinder (2 x 10mL, 1 x 25mL, 2 x 100mL)
 * Volumetric Flask (1000mL)
 * Dish Soap
 * Stirring rod
 * Temperature probes (7)
 * Water from various sources
 * Pipettes
 * Goggles
 * Gloves
 * Wash bottle
 * Stop watches(3)
 * Hot plate
 * Calcium Nitrate- Ca(NO3)2
 * Silver nitrate – AgNO3
 * 5% Nitric acid (100mL) - NO3
 * Balance
 * Stopwatches (3)
 * Black construction paper


 * __ Procedure: __**
 * Before the experiments **
 * 1) Fill each 500mL beaker, each with water from a different source, including tap water (from the 1st Floor Science bathroom), bottled water, distilled water, pond water (from the lower school pond), pool water, and dispenser water (from the water dispenser in front of the summer school activities office).
 * 2) Put one temperature probe into each beaker. Wait until each sample is at 24.6° C before starting the experiment. If not, use a hot plate to change the temperature.

** Chloride Presence **
 * pH and Dissolved Oxygen Experiments **
 * 1) Calibrate pH and dissolved oxygen probe. The pH probe is calibrated through two-point calibration with buffers of pH 4 and pH 7. The dissolved oxygen probe is calibrated through internal calibration.
 * 2) Fill 5 of the 100mL beakers with 60mL of tap water.
 * 3) Using LoggerPro, pH probe, and dissolved oxygen probe, measure the pH value and dissolved oxygen value of the water over a 1 minute time period. Keep the probes in motion while measuring.
 * 4) Record the average value of the best fit line of the pH and dissolved oxygen graphs.
 * 5) Repeat steps 3 –4 for 4 more trials of the same sample water.
 * 6) Repeat steps 2 – 5 for other water sources.
 * 1) Prepare 5% nitric acid in a 500mL beaker.
 * 2) Prepare a silver nitrate solution using 1.7 grams of silver nitrate and 98mL of distilled water. The silver nitrate solution is light sensitive and is to be kept under a cover made from black construction paper whenever possible.
 * 3) Prepare a test tube with 25mL of tap water.
 * 4) Put two drops of nitric acid into the test tube using a pipette. Mix the test tube thoroughly. If there is fizzing, wait until the fizzing stops before continuing to the next step.
 * 5) Put two drops of silver nitrate solution into the test tube. Mix the test tube thoroughly and record and observations regarding the presence of precipitate.
 * 6) Repeat steps 3 – 6 for the six other water sources.




 * Calcium Hardness **
 * 1) Pour 40mL of the water sample into a 100mL graduated cylinder.
 * 2) Add 0.4mL of soap into the graduated cylinder.
 * 3) Shake the cylinder up and down 3 times.
 * 4) Let the solution settle for 2 minutes.
 * 5) Measure the height of the soap bubbles using a ruler.
 * 6) Repeat steps 2-5 for 4 more trials
 * 7) Repeat steps 1-6 with the other water samples.
 * 8) Create a hard water sample by mixing 110mg of calcium nitrate into 500mL of tap water.
 * 9) Repeat steps 1-6 with the hard water sample.



__**Data Collection** __


 * Table 1 – pH Values of Different Water Sources **


 * ** Water Source ** ||||||||||  ** pH Values (1 - 7) **  ||
 * ^  ||||||||||  ** Trials **  ||
 * ^  ||  ** 1 **  ||  ** 2 **  ||  ** 3 **  ||  ** 4 **  ||  ** 5 **  ||
 * Tap ||  6.21   ||   6.32   ||   6.38   ||   6.42   ||   6.42   ||
 * Bottled ||  7.96   ||   7.64   ||   7.50   ||   7.85   ||   7.75   ||
 * Distilled ||  6.88   ||   7.80   ||   7.90   ||   6.99   ||   6.22   ||
 * Pond ||  7.39   ||   7.19   ||   7.16   ||   7.21   ||   7.17   ||
 * Pool ||  6.50   ||   6.87   ||   6.85   ||   7.06   ||   7.17   ||
 * Fountain ||  6.39   ||   6.30   ||   6.28   ||   6.28   ||   6.25   ||
 * Dispenser ||  7.74   ||   7.55   ||   7.23   ||   6.66   ||   5.77   ||


 * Table 2 – Dissolved Oxygen Values of Different Water Sources **


 * ** Water Source ** ||||||||||  ** Dissolved Oxygen (mg/L) **  ||
 * ^  ||||||||||  ** Trials **  ||
 * ^  ||  ** 1 **  ||  ** 2 **  ||  ** 3 **  ||  ** 4 **  ||  ** 5 **  ||
 * ** Tap ** ||  4.40   ||   3.20   ||   3.00   ||   3.60   ||   2.90   ||
 * ** Bottled ** ||  1.90   ||   2.20   ||   2.10   ||   2.20   ||   2.20   ||
 * ** Distilled ** ||  2.30   ||   3.70   ||   2.00   ||   2.20   ||   2.10   ||
 * ** Pond ** ||  2.80   ||   1.80   ||   3.20   ||   3.20   ||   2.80   ||
 * ** Pool ** ||  2.90   ||   2.70   ||   3.00   ||   2.90   ||   3.10   ||
 * ** Fountain ** ||  4.70   ||   3.80   ||   5.40   ||   3.50   ||   4.00   ||
 * ** Dispenser ** ||  1.80   ||   2.00   ||   2.20   ||   2.20   ||   1.70   ||


 * Table 3 – Presence of Chloride – Precipitate Observations **


 * ** Water Source ** || ** Precipitate Present (Yes / No) ** || ** Data Observations ** ||
 * ** Tap ** || Yes || A medium amount of precipitate formed, showing moderate chloride levels. ||
 * ** Bottled ** || Yes || Very little precipitate formed, showing a very low chloride levels. ||
 * ** Distilled ** || No || No precipitate observed, showing that an unobservable, insignificant amount of chloride. ||
 * ** Pond ** || Yes || A medium amount of precipitate formed, showing moderate chloride levels. ||
 * ** Pool ** || Yes || A high amount of precipitate formed, showing high chloride levels. ||
 * ** Fountain ** || Yes || A medium amount of precipitate formed, showing moderate chloride levels. ||
 * ** Dispenser ** || Yes || Some precipitate observed, showing low chloride levels. ||


 * Table 4 - Calcium Hardness of Water Test- The Height of Soap Bubbles **


 * || Trial 1 (cm) || Trial 2 (cm) || Trial 3 (cm) || Trial 4 (cm) || Trial 5 (cm) || Average (cm) ||
 * Fountain water || 9.00 || 8.60 || 8.50 || 9.00 || 8.80 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">8.78 ||
 * <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">Distilled water || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">11.5 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">11.2 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">11.2 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">11.4 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">12.0 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">11.46 ||
 * <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">Pool Water || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.40 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.60 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.20 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.30 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.30 ||
 * <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">Water dispensers || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.50 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.30 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.10 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.50 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.28 ||
 * <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">Pond water || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">6.70 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">6.60 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">7.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">6.86 ||
 * <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">Bottled water || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.20 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.10 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.40 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.14 ||
 * <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">Tap || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">9.30 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">9.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">9.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">8.80 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">8.60 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">8.94 ||
 * <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">Calcium || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.80 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.90 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">6.00 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.90 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">6.10 || <span style="color: #000000; display: block; font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px; text-align: center;">5.94 ||

__**Data Processing & Analysis**__
 * Table 5 – Average pH Value and Standard Deviation of Different Water Sources **
 * ** Water Source ** || ** Average pH Values (1 - 7) ** || ** Standard Deviation ** ||
 * Tap ||  6.35   ||   0.088   ||
 * Bottled ||  7.74   ||   0.179   ||
 * Distilled ||  7.16   ||   0.698   ||
 * Pond ||  7.22   ||   0.095   ||
 * Pool ||  6.89   ||   0.256   ||
 * Fountain ||  6.30   ||   0.053   ||
 * Dispenser ||  6.99   ||   0.795   ||

Sample Calculation (for Tap Water):

Standard deviation was calculated using Microsoft Excel 2007.

Using the average and standard deviations of the pH values, the following was determined: Tap and fountain water had pH values significantly lower than the optimum pH value drinking water (pH 7.5).


 * Table 6 – Average Dissolved Oxygen Value and Standard Deviation of Different Water Sources **
 * ** Water Source ** || ** Average Dissolved Oxygen (mg/L) ** || ** Standard Deviation ** ||
 * Tap ||  3.42   || ||
 * ottled ||  2.12   ||   0.130384048   ||
 * Distilled ||  2.46   ||   0.702139587   ||
 * Pond ||  2.76   ||   0.572712843   ||
 * Pool ||  2.92   ||   0.14832397   ||
 * Fountain ||  4.28   ||   0.766159252   ||
 * Dispenser ||  1.98   ||   0.228035085   ||

Sample Calculation (for Tap Water):




 * Graph 1 - Average pH Value of Different Water Sources **

Error bars were drawn using standard deviation values.


 * Graph 2 - Average Dissolved Oxygen Value of Different Water Sources **

Error bars were drawn using standard deviation values.


 * Graph 3 - Testing for Calcium: Height of Soap Bubbles**

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif;">

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">**Conclusion**

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">Hardness of water: <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">From the results, it can be inferred that calcium reduces bubble formation. Soap produces less bubbles with calcium and magnesium because it reacts to form the calcium or magnesium salt of the organic acid of the soap. These salts form the grayish scum in the bubbles, and reduces the amount of bubble that can be formed. The bottled water has the lowest height of bubbles formed, while the distilled water has the highest height of soap bubbles. The fountain water is found to be in the middle. The bottled water may have other minerals that would affect the results. However, "hard water" is not a health hazard because it contributes a very small amount of calcium towards daily intake needs.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">**Evaluation**

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">Hardness of water: <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">It is very hard to determine the height of bubbles. We weren't sure where the bubbles ended, as there were many different types of bubbles. Closer to the solution, the bubbles were small and concentrated, and further higher in the test tube, the bubbles became bigger and less in number. The big bubbles could have reached to the top of the test tube, but the small bubbles did not take up a lot of space. We tried to make the measuring of the bubbles consistent by measuring the small bubbles only, but there could have also been a big systematic error as it was hard to determine where the small bubbles end and the big bubbled begin. To decrease the systematic error, more trials should have been run for each of the water samples so a general norm of height can be found.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">Another potential error was that different people shake the cylinder differently, therefore creating a variation in results. The force of each shake was also different, so the height from the resulting shakes would vary. The same person should have shook the test tubes and try to shake the tubes with consistent force. Another systematic error is in the measuring of the amount of soap. 0.4 ml is very hard to measure out.

<span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">**Sources** <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 110%;">**[]** <span style="font-family: 'Trebuchet MS',Helvetica,sans-serif; font-size: 14.6667px;">[]