Water Quality: A Simple Comparative Analysis Using Electrical Conductivity
Haresh M, Juan S, Juan A, Saad A
12 March 2018
CUNY City College of New York
ENGL 21007-Writing for Engineers
2018 Spring
Professor Alikhani
Table of Contents
Abstract…………………………………………………………………………………………….2
Introduction…………………………………………………………………………………………3
Methods and Materials…………………………………………………………………………….4
Procedure………………………………………………………………………………………….4
Results……………………………………………………………………………………………..6
Discussion………………………………………………………………………………………….6
Conclusion…………………………………………………………………………………………7
References………………………………………………………………………………………….8
Abstract
Because we drink the water at CCNY almost everyday, if not everyday, it is imperative that we understand the quality of the water that we drink while we are here. This study explored the electrical conductivity of water using different common solutes, which is a way of testing water quality used by the EPA. We tested tap water, distilled water,and a baking soda water solution. We used a simple circuit, setting up two wires connecting from the battery, voltmeter, and the different solutions. The results suggested that the baking soda water solution was the only one that conducted electricity effectively, out of our test choices. We can conclude that distilled and tap water are less conductive than baking soda, however due to errors in our experiment we can not conclude a precise estimate of how different the tap water is from the distilled water.
Introduction
Electrical energy exists all around us. We utilize electrical energy to power things in our everyday lives such as computers, televisions, home appliances, lighting, and even cars. For all of these devices to operate, they need to be designed in a way that includes some sort of material, which allows for the conductivity of electrical energy. Electrical conductivity can be defined as “the measure of the amount of electrical current a material can carry or it’s ability to carry a current” (Helmenstine, 2017b). While conductivity is often thought of as significant in terms of its ability to power electronic devices, it also plays an important purpose related to its measurement in liquids.
Scientists and researchers are particularly interested in the measurement of electrical conductivity in water. This measurement is significant because it is used as an indicator for determining water quality, or a general measurement pertaining to levels of salinity or pollution (Whetzel, 2017). For a liquid to be considered a strong conductor of electricity, it must consist of inorganic chemicals that break down when mixed with a liquid and produce small electrically charged particles called ions (Environmental Monitor, 2010). Four of the most common ions found in water are sodium, chloride, calcium, and magnesium (Environmental Monitor, 2010). Baking soda, for example, is a salt that produces a bicarbonate ion called carbon-dioxide. In contrast, pure water, or distilled water, has no ions and is therefore considered an insulator (Perlman, 2016). An insulator, is a material that does not allow an electrical current to flow freely, such as wood, glass, clay, or plastic (Helmenstine, 2017a). Insulators are very poor electrical conductors. Furthermore, a material that is a poor electrical conductor, possesses greater resistance. Resistance can be measured by the voltage drop, or the loss of volts (Hoffman, 2006). Therefore, the less number of volts lost, the more conductive a material will be.
We have designed an experiment to test the quality of the tap water at CUNY City College of New York by measuring its electrical conductivity and comparing it to that of distilled water, and distilled water with baking soda. A review of the academic literature related to electrical energy and the conductivity of liquid solutions shows that solutions with a greater number of ions are more electrically conductive than others, and are therefore considered to be poorer quality. Based on our research, we predict that the school’s tap water will be conductive and it’s quality will be significantly more similar to that of distilled water compared to the distilled water with baking soda. Additionally, we predict that the distilled water will show the greatest amount of resistance, and the distilled water with baking soda will show the least amount of resistance.
Methods and Materials
Materials :
- 1 (9 volt) battery
- 1 gallon of distilled water
- 2 (12 inch) wires
- 1 tablespoon of baking soda
- 1 measuring cup
- 1 roll of electrical tape
- 1 Voltmeter
8.1 gallon of Tap water
- 2 (16 oz) container
Procedure:
- First of all attached the wires to the battery ,one with the positive and other with the negative terminal of the battery. Use electrical tape to hold wires with the battery.
- In order to calculate voltage(V) and current(I) across each mixtures attach red wire with the positive and black wire with the negative terminal of voltmeter . Now connect the black wire from voltmeter with the wire attached to the negative terminal of battery. Set up voltmeter at 20 volts. We can see this in figure 1 below.
Equipment Setup
Figure 1( Saad Arshad-2018)
- Rinse out beaker with distilled water to get rid of any contaminants and fill the container with 100 mL of distilled water.
- Dip the wire from positive terminal of the battery and the red wire into the container with distilled water . Read the voltage and current across distilled water on voltmeter .
- Now test regular tap water filled with in 100 mL in container determine the difference. Repeat step 4.
- Now rinse out your container with distilled water. Pour more 100 mL of distilled water into your container and add tablespoon of baking soda. Stir it and put the wires again into container. Repeat step 4.
Results
Battery 7.95 Volts, 1.48 Amps
Voltage and Current Measurements of Solutions
| Solutions | Voltage (Volts) | Current (Amps) |
| Distilled Water | 7.37 | 0.00 |
| Baking Soda with Distilled Water | 7.56 | 0.10 |
| Tap Water | 7.27 | 0.00 |
Table 1: Data of voltage and current measurements of the three solutions in our experiment.
Discussion
The voltage across distilled water was measured to be 7.37 volts with a current of 0 amps. On the other hand, the voltage across baking soda with distilled water measured to be 7.56 volts with a current of 0.10 amps. Therefore, the addition of baking soda to the distilled water resulted in an increase in voltage and current. Based on our results, baking soda conducts electricity better than the two other solutions. Baking soda is an ionic compound that does not conduct electricity when it is a solid. However, when dissolved in water and becomes liquid, baking soda becomes conductive. This was an interesting part of our experiment because we observed bubbles when measuring the voltage and current through this mixture with the voltmeter. The bubbles, which did not appear when testing the other solutions, indicated that the ionic compounds of the baking soda broke down into separate ions when dissolved in the distilled water. As a result, the solution became conductive. As shown in Table 1, tap water and distilled water conducted 0 amps of current. The distilled water, the control solution in our experiment, is considered an insulator. There are no impurities or ions in distilled water, only neutral water molecules (Perlman, 2016). However, tap water does have impurities and ions. Therefore, the resistance of distilled water should be greater than the resistance measured for the tap water. Since both measurements read 0 amps and the tap water measured a greater voltage drop than the distilled water, it is clear that there must have been an error in our measurements.
There are some errors that may have impacted our results. For example, The 9V battery actually measured to be 7.95V. The loss of 1.05V may have affected how the voltages of the water mixtures were measured. Furthermore, we might have not been perfect when measuring one tablespoon of baking soda for baking soda and distilled water experimental test. Also, cross contamination between liquid solutions may have been possible while conducting our experiment. These errors and the ones we overlooked all contribute to our results being slightly inaccurate.
Conclusion
We believe that our results may be slightly inaccurate. For instance, based on the measurements for current of the distilled water, tap water, and distilled water with baking soda, we can not draw an accurate conclusion for our first hypothesis. The results show that the tap water at CCNY is most similar to distilled water which would make sense due to the large quantities of ions present in the distilled water with baking soda. However, the results also show that the tap water is just as pure as the distilled water. This would make sense if the bathroom sinks at CCNY have water filters built in to them. However, there are no filters placed on the faucets in the bathroom sinks. Like other sources of tap water throughout New York City, the tap water at CCNY is not filtered to the same extent as distilled water because it has to travel through multiple systems of pipes that may potentially leave traces of inorganic chemicals. In turn, these inorganic chemicals would break down when mixed with the water and produce ions that would increase the conductivity of the water. While we expected the distilled and tap waters to be most similar, we also expected some level of current for the tap water. This variation would have helped us determine a more accurate conclusion on how closely similar the two solutions are.
Our second hypothesis regarding the measurement of resistance with respect to each liquid solution is also inconclusive. Because distilled water is considered to be an insulator, it’s level of resistance should have measured the highest. However, our results show that the tap water had a higher level of resistance. We believe this result may be inaccurate because tap water is expected to consist of traces of ions which would mean that there is less resistance, and therefore more conductive.
Errors in our experiment such as the loss of voltage in the battery and cross-contamination between liquid solutions, should be addressed and corrected for future experiments. For example, future experiments should consist of brand new batteries for each test and the experimenters must rinse the containers thoroughly as well as clean the wires that are dipped into the different liquid solutions. Additionally, in order to get a better sense of how similar tap water at CCNY is to distilled water, future experiments should test the conductivity of multiple liquid solutions that consist of different types of inorganic chemicals. This would allow us to create a better spectrum for our results, and therefore a better understanding of the quality of tap water at CCNY.
References
Fondriest Staff. (2010, August 12).What is Conductivity? Environmental Monitor. Retrieved
from http://www.fondriest.com/news/what-is-conductivity.htm
Helmenstine, Anne Marie, Ph.D. (2017a, October 3). 10 Examples of Electrical Conductors and
Insulators. Retrieved from https://www.thoughtco.com/examples-of-electrical-conductors
-and-insulators-608315
Helmenstine, Anne Marie, Ph.D. (2017b, February 15). Electrical Conductivity Definition.
Retrieved from https://www.thoughtco.com/definition-of-electrical-conductivity-605064
Hoffman, Pete. (2006) Understanding & Calculating Series Circuits Basic Rules. Retrieved from
https://www.swtc.edu/ag_power/electrical/lecture/series_circuits.htm
Perlman, Howard. (2016, December 02). Electrical Conductivity and Water. The USGS Water
Science School. Retrieved from https://water.usgs.gov/edu/electrical-conductivity.html
Whetzel, Joan. (2017, April 25). Why Is Conductivity Important? Sciencing. Retrieved from
http://sciencing.com/conductivity-important-6524603.html
