Topic: Water Safety Experimenters: Andrew, Azri, Vickie, Jacci, Melody Research Question: What are differences in pH level, calcium, and chlorine in varying water sources at TAS? Underlying Question: Which water sources are safe for drinking?
Aim: To observe and evaluate the different water qualities in TAS through measurements of pH, mineral, and chlorine levels to determine which water sources are safe for drinking.
Condition
Explanation
Independent Variable: Different types of water (Pool Water, Drinking Fountain Water, Tap Water, Water Dispenser water)
Four primary water sources found in Taipei American School are selected to measure and compare the pH, amount of Chlorine and Calcium in the solutions.
Dependent Variable: Levels of pH, Amount of chlorine, magnesium, calcium
The tested factors were selected to ensure that the water is safe for drinking in drinking water, and that the water is safe for the human body in swimming water.
Control Group: Deionized water
Theoretically deionized water should not contain high traces of chemicals. Therefore it is used as the control group for the experiment.
Control Variable: Quantity of Water
The quantity of the water used in the actual experiment should be kept constant. Particularly in the experiment measuring for calcium and chlorine.
Control Variable: Temperature of Solution
Because temperature is not the independent variable, it should be kept constant throughout the experiment. For this lab, the experiment will be conducted in room temperature of approximately 23 degrees Celsius.
Control Variable: Light Intensity
Light intensity is also not a factor measured in the experiment. To ensure that the light intensity remain constant, conduct the experiment in the same location with the same light source.
Control Variable: Consistency in Equipment
The equipment used for measurement should be consistent throughout the experiment. For example when measuring for pH, if possible use the same pH probe to ensure the most accurate data.
Material
Quantity
400mL Beaker
Five
100mL Beaker
Five
Temperature Probe
Five
pH Probe
One
Computer with Loggerpro
One
pH Calibrating solution
20mL
Measuring Cylinder
Two
Pipette
Four
Pool water, drinking fountain water, tap water, water dispenser water, deionized water
500mL each
soap
20mL
Nitric acid solution
10mL
Silver nitrate solution
10mL
50 mL Test tube
Six
Stop watch
One
Parafilm
30cm
Scissors
One
Test tube rack
One
A4 size black paper
One
Tape
One roll
Filtration Tube
One
Large Test Tube (100ml)
One
Procedure:
Preparatory Stage: 1) Collect water samples from different conditions 2) Pour samples into 400mL beakers and label beakers accordingly
Measuring pH: 3) Using a measuring cylinder, pour 50mL of pool water into a 100mL beaker 4) Set up Loggerpro and calibrate one pH probe 5) Measure pH of pool water 6) Repeat steps 3-5 five times 7) Repeat steps 3-6 for deionized water, fountain water, tap water, and water dispenser water
Measuring Magnesium and Calcium: 8) Using a measuring cylinder, pour 20mL of pool water into a 50mL measuring cylinder 9) Pour 1mL of soap into the cylinder 10) Seal the opening with parafilm and swirl the cylinder in circular motion for one minute 11) Remove the plastic wrap and measure the height of bubbles 12) Repeat steps 8-11 five times 13) Repeat steps 8-12 for deionized water, fountain water, tap water, and water dispenser water
Measuring for Chlorine: 14) Prepare diluted (5%) nitric acid solution 15) Prepare Silver nitrate test solution (dissolve 1.7 grams of silver nitrate crystals into 98 ml of distilled water. Store in dark background) 16) Place 20ml of pool water into a clean test tube 17) Add two drops of diluted nitric acid. 18) Shake the solution to mix. If the solution fizzes, continue to add acid until the fizz stops. 19) Hold up test tube to strong light source on one side with a dark side behind the test tube. Add two drops of Silver nitrate test solution. 20) Observe sample and record data. 21) Repeat steps 14-20 five times 22) Repeat steps 14-21 for deionized water, fountain water, tap water, and water dispenser water
Table 1: pH Levels of Varying Water Sources (Measured using a pH probe)
Be sure to calibrate pH probe prior to experimentation
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Mean
T-Test
Standard Deviation
% of STDEV
Pool Water
6.30
6.52
6.74
6.94
5.81
6.46
0.00
0.44
7%
Deionized Water (Control)
7.50
7.11
7.45
7.32
7.12
7.30
1.00
0.18
2%
Water Dispenser
7.22
7.96
7.63
7.64
7.49
7.59
0.08
0.27
4%
Tap Water
6.60
6.20
6.18
6.27
5.88
6.23
0.00
0.26
4%
Water Fountain
6.35
5.81
6.11
6.26
6.18
6.14
0.00
0.21
3%
Graph 1:pH Levels of Varying Water Sources (Measured using a pH probe)
Be sure to calibrate pH probe prior to experimentation
Error bars reflect the standard deviation (shown in Table 1)
Results and Explanations:
The data reveals certain trends of pH levels in the different water sources. In pool water, the pH level was generally around 6.00, and the mean was 6.46. This indicates that the pH level in pool water is slightly more acidic than the optimum pH level of 7. In deionized water, the pH level was around 7, with a mean of 7.3, thus indicating that the pH level of the deionized water is at its optimum level. In the water dispenser water, the mean of the pH levels gathered from all 5 trials was 7.58 which means that the pH level of the water dispenser water is slightly more basic than the optimum level for pH. The mean pH level of tap water was 6.2 which is slightly more acidic than the optimum pH level. Lastly, the mean of the pH level in the water fountain was 6.14 which is also slightly more acidic than the optimum pH level. From these results, one can deduce that pH levels in deionized water was close to the optimum pH level compared to water from the other sources. The pH in pool water, tap water, and the water fountain was found to be more acidic than usual, while the pH in the water dispenser water was more basic. This could be attributed to the unequal balance of hydrogen and hydroxide ions within the different water sources which resulted in a variation of pH levels.
Procedure and Method
Evaluation of the Procedure or Method
Suggestions for Improvement
Range of independent variable
The source of water is the independent variable tested. The five sources selected were an appropriate representation of the sources of water available at the campus of TAS.
To improve the experiment the sources of water could be expanded to include sewage water and bottled water for a more comprehensive report.
pH was measured with pH probes
The pH of the solution could change with exposure to light and carbon dioxide.
In the future for more accurate results, light exposure should be minimized (conduct the experiment in minimal light setting).
5 trials were completed at each temperature
Having five trials allow for relatively accurate results. Five trials allow the experimenter to observe trends in results and identify outliers in the set of data.
To make the results more accurate, more trials could be completed to further increase the accuracy of the results.
Equipment
pH Probes: pH probes accurately measure the pH level. However the accuracy of the pH probe could depend on the condition of the probes.
Because of the precision of the tools and human errors, the accuracy of the results may have been compromised.
pH Probes: In the future be sure to calibrate the pH probes prior to experimentation to the higher degree of accuracy.
Table 2:Calcium in Varying Water Sources (Measured through height of bubbles) Data Result
Trial 1 (cm)
Trial 2 (cm)
Trial 3 (cm)
Average (cm)
Pool Water
6.5
7
6.9
6.8
Deionized Water
12.5
12.12
12.8
12.5
Water Dispenser
9.5
9.7
9.3
9.5
Tap Water
9
8.8
9.2
9.0
Water Fountain
8.5
8.9
8.7
8.7
Hardened Water (200mg/l) ddH2O + Ca(NO3)2
6.3
6.1
5.7
6.0
Calculation e.g. Pool Water 12.5 cm bubbles/1 cm3 = 6.8 cm/x cm3 soap X = volume of soap needed to create 12.5 cm of bubbles
Average (cm)
X (cm)
Pool Water
6.8
0.5
Deionized Water
12.5
1.0
Water Dispenser
9.5
0.8
Tap Water
9.0
0.7
Water Fountain
8.7
0.7
Hardened Water (200mg/l) ddH2O + Ca(NO3)2
6.0
0.5
Conclusion: The control group used to measure an appropriate level of bubbles was the the deionized water, as it could be assumed that no calcium ions were present. The calcium present reacted with the ethylene glycol monostearate in the soap to prevent the formation of bubbles. Originally, the setup of the lab measured the total height of bubble formation with a constant amount of soap added to each sample of water (1 ml). However, using the height of bubble formation in deionized water, ratios could be derived to discover the corresponding amount of soap needed to create the same height of bubbles for the other compounds. The less soap necessary for forming a bubble height of 12.5 cm, the harder the water (higher concentration of calcium present). The manipulated data indicates that the pool water had the highest calcium concentration, followed by the tap water and fountain water (equal amounts of soap necessary), the water from the dispenser, and finally the deionized water. Even though the hardness of water is not directly detrimental to the health of an individual, it can cause the breakdown of equipment.
Possible sources of error: 1. Keeping a constant force when shaking the solution, which determines the height of the bubbles. 2. The errors of reading the bubbles height; bubbles consist of air in between, which made it hard to make an accurate measurement of the height
Table 3: Level of Chlorine in Varying Water Sources (Higher precipitation reflects higher chlorine concentration)
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Mean
Pool Water
High Precipitation
High Precipitation
High Precipitation
High Precipitation
High Precipitation
High Precipitation
Deionized Water (Control)
No Precipitation
No Precipitation
No Precipitation
No Precipitation
No Precipitation
No Precipitation
Water Dispenser
Low Precipitation
No Precipitation
No Precipitation
No Precipitation
No Precipitation
No Precipitation
Tap Water
Medium Precipitation
Medium Precipitation
Medium
Medium Precipitation
Medium Precipitation
Medium Precipitation
Water Fountain
Low Precipitation
Low Precipitation
Low Precipitation
Low Precipitation
Low Precipitation
Low Precipitation
Description of Results
Significance/ Explanation of Results
Pool water illustrated high signs of precipitation
- Since pool water uses chlorine as a disinfectant, it is obvious that it will show high signs of precipitation after silver nitrate solution and nitric acid solution, which are used to detect chloride, are added. Precipitation is created through is the reaction of the contact of chloride, silver nitrate, and nitric acid.
Deionized water is the control variable. It showed no signs of precipitation
- Since deionized water is a kind of water that is physically processed to remove any kinds of impurities, there won’t have any chloride in it, thus no precipitation.
Water dispenser water showed no signs of precipitation
- Water dispenser water shows similar characteristics to deionized water, thus no precipitation.
Tap water showed medium precipitation
- Since tap water is only potable water, which is only water clean to a certain extent with fairly low risks of harm, it contains impurities such as chloride, thus precipitation.
Water fountain water showed low precipitation
- Water fountain water shows similar traits to tap water as it isn’t intended for long usage, it has some or little chloride, thus there is a low amount of precipitation.
Procedure and Method
Evaluation of the Procedure or Method
Suggestions for Improvement
Prepare silver nitrate solution and set in the dark
Silver nitrate solution is light sensitive therefore light exposure must be kept to a minimum.
In the future, the experiment could be conducted in the dark to avoid exposure to light outside of actual experimentation
Add two drops of dilute nitric acid
The quantity of dilute nitric acid added to the water source is not specific enough. This could have resulted in different levels of precipitation.
Apparatus should be kept constant (use the same pipette throughout the entire experiment)
Shake the solution to mix
In the first part silver nitrate was added water to form the silver nitrate solution. The silver nitrate crystals could have set in the bottom of the beaker after some time.
Be sure to thoroughly mix the silver nitrate test solution before commencing the experiment
Five trials
Five trials allow for accurate results and standard deviation so that different results can be compared.
In the future for more accurate results, more trials could be completed.
Topic: Water Safety
Experimenters: Andrew, Azri, Vickie, Jacci, Melody
Research Question: What are differences in pH level, calcium, and chlorine in varying water sources at TAS?
Underlying Question: Which water sources are safe for drinking?
Aim: To observe and evaluate the different water qualities in TAS through measurements of pH, mineral, and chlorine levels to determine which water sources are safe for drinking.
Procedure:
Preparatory Stage:
1) Collect water samples from different conditions
2) Pour samples into 400mL beakers and label beakers accordingly
Measuring pH:
3) Using a measuring cylinder, pour 50mL of pool water into a 100mL beaker
4) Set up Loggerpro and calibrate one pH probe
5) Measure pH of pool water
6) Repeat steps 3-5 five times
7) Repeat steps 3-6 for deionized water, fountain water, tap water, and water dispenser water
Measuring Magnesium and Calcium:
8) Using a measuring cylinder, pour 20mL of pool water into a 50mL measuring cylinder
9) Pour 1mL of soap into the cylinder
10) Seal the opening with parafilm and swirl the cylinder in circular motion for one minute
11) Remove the plastic wrap and measure the height of bubbles
12) Repeat steps 8-11 five times
13) Repeat steps 8-12 for deionized water, fountain water, tap water, and water dispenser water
Measuring for Chlorine:
14) Prepare diluted (5%) nitric acid solution
15) Prepare Silver nitrate test solution (dissolve 1.7 grams of silver nitrate crystals into 98 ml of distilled water. Store in dark background)
16) Place 20ml of pool water into a clean test tube
17) Add two drops of diluted nitric acid.
18) Shake the solution to mix. If the solution fizzes, continue to add acid until the fizz stops.
19) Hold up test tube to strong light source on one side with a dark side behind the test tube. Add two drops of Silver nitrate test solution.
20) Observe sample and record data.
21) Repeat steps 14-20 five times
22) Repeat steps 14-21 for deionized water, fountain water, tap water, and water dispenser water
Table 1: pH Levels of Varying Water Sources (Measured using a pH probe)
Graph 1: pH Levels of Varying Water Sources (Measured using a pH probe)
Results and Explanations:
The data reveals certain trends of pH levels in the different water sources. In pool water, the pH level was generally around 6.00, and the mean was 6.46. This indicates that the pH level in pool water is slightly more acidic than the optimum pH level of 7. In deionized water, the pH level was around 7, with a mean of 7.3, thus indicating that the pH level of the deionized water is at its optimum level. In the water dispenser water, the mean of the pH levels gathered from all 5 trials was 7.58 which means that the pH level of the water dispenser water is slightly more basic than the optimum level for pH. The mean pH level of tap water was 6.2 which is slightly more acidic than the optimum pH level. Lastly, the mean of the pH level in the water fountain was 6.14 which is also slightly more acidic than the optimum pH level. From these results, one can deduce that pH levels in deionized water was close to the optimum pH level compared to water from the other sources. The pH in pool water, tap water, and the water fountain was found to be more acidic than usual, while the pH in the water dispenser water was more basic. This could be attributed to the unequal balance of hydrogen and hydroxide ions within the different water sources which resulted in a variation of pH levels.
Procedure and Method
Evaluation of the Procedure or Method
Suggestions for Improvement
Because of the precision of the tools and human errors, the accuracy of the results may have been compromised.
Table 2: Calcium in Varying Water Sources (Measured through height of bubbles)
Data Result
ddH2O + Ca(NO3)2
Calculation
e.g. Pool Water
12.5 cm bubbles/1 cm3 = 6.8 cm/x cm3 soap
X = volume of soap needed to create 12.5 cm of bubbles
Possible sources of error:
1. Keeping a constant force when shaking the solution, which determines the height of the bubbles.
2. The errors of reading the bubbles height; bubbles consist of air in between, which made it hard to make an accurate measurement of the height
Table 3: Level of Chlorine in Varying Water Sources (Higher precipitation reflects higher chlorine concentration)
High Precipitation