iECOshare [Water Conductivity Sampling and Data Share] PROGRAM OVERVIEW In this program students will build a Water Conductivity Tester to test the water purity of samples they collect from local area ponds, brooks and other supervised water areas. Each school will be able to allow students to participate in a data-sharing website managed by RoboAchiever where their findings can be uploaded and shared in common with that of other reporting schools or each school’s respective Science Club.
Our program is inspired by the Hydrosphere Data Entry Protocal established by the Globe Worldwide Science and Education Program. RoboAchiever’s Founder and program developer, Don Bertrand, is a trained and authorized Hydrosphere Data-Entry User. Consistent with the goals of that organization, our program follows the curriculum set forth on the TeachEngineering.com website “Build and Test a Conductivity Probe with Arduino.” Our standard program is conducted over a period of 12 weeks with two 2-hour sessions per week. RoboAchiever Learning Systems 5 Science Park at Yale, New Haven, CT 203 430-3141 www.roboachiever.com
ARDUINO ELECTRONICS AND CODING We begin the program with an introduction to the Arduino microcontroller that is used to sense the environment and trigger report output based on the data results. In teams of 4, students will build digital circuits and write code on the Arduino platform to monitor data input and respond as directed. Several circuits will be selected for this instruction from the Adafruit ARDX Experimentation Kit for Arduino. https://www.adafruit.com/product/170
THE WATER CONDUCTIVITY TESTER [Source: TeachEngineering.com website “Build and Test a Conductivity Probe with Arduino.”]
Introduction With their facility to now code the Arduino microcontroller, students will construct a simple conductivity probe to test and compare various liquid samples, before heading out to the field. Certain math skills will be enhanced as students prepare different sampling mixtures to measure and report on comparative data results for the different mixtures. Engineering Connection Engineers often design sensors to fit their exact needs. Or example, planning solar panel installations requires sensors that measure the amount of light falling on a given area. In designing a desalination plant, engineers must be able to measure the amount of salt present in seawater and in the fresh water produced; a conductivity probe is a valuable instrument to identify the presence or absence of ionic compounds.
Through this lab, students are exposed to multiple ways that a conductivity probe can be used and challenged to consider its possible realworld applications. The primary function of the probe is to indicate the ease with which electrical current can flow through a solution; the easier current flows, the higher the conductivity. This single measurement determines whether an aqueous solution contains ionic or covalent solutes, an important first step in characterizing unknown solutions.
Learning Objectives • After this activity, students should be able to: • Identify whether a solution is conductive. • Construct a functional conductivity probe. • Integrate a conductivity probe into a simple circuit. • Utilize an Arduino with LCD display to display • probe values. • Determine the conductivity of an unknown solution. Introduction/Motivation Have you ever wondered why you have to get out of the swimming pool when a thunderstorm approaches? It has everything to do with conductivity—the ability of a solution to conduct electrical current. A solution conducts electrical current when charged particles (ions) are in the aqueous solution. The movement of these positive and negative ions enables the flow of charge through the solution. In this lab activity, we will make a probe to use as a tool to determine very quickly whether a solution conducts electricity (ZAP!!) or not. Fundamentally, the probe measures the resistance to the flow of charge and must be submerged within the testing solution to work. If the solution contains ions, charge will be able to flow easily through the probe (the resistance will be low). However, if the solution contains only water molecules or a solution of water and other covalent solutes, no charged particles exist to facilitate the flow of charge so the resistance across the probe will be very high. Procedure This lab activity requires students to make simple solutions by dissolving various solutes into measured volumes of water. Depending upon the solute, the resulting solution will either conduct electricity of varying degree or be nonconductive. Conductive solutions always result from the presence of a solute that is ionic, meaning it dissociates in water into charged particles called ions. When an ionic substance dissociates, both positive cations and negative anions form, and both are necessary to enable a solution conduct an electrical current. The conductivity of a
solution depends upon the amount of ions presentÍž therefore, more concentrated ionic solutions have a higher conductivity than more dilute solutions. Outside of the chemistry classroom, students may have heard of "electrolytes" and "nonelectrolytes," words that are synonyms for ionic compounds and covalent compounds, respectively. The measurement of conductivity is typically a measure of how easily electrical current is able to move through a solution. The higher the conductivity of a solution, the less resistance to the flow of electrical current. This is the basis for the conductivity probe that students fabricate and use. The probe measures resistance and translates the resistance as an indicator of conductivity. Hence, if the solution has a high resistance, such as with a nonelectrolytic solute, the conductivity will be very low and if the solution has a low resistance, such as with an electrolytic solute like table salt, the conductivity will be very high. The conductivity probe uses simple electrical circuits to communicate the measurement to the user.
LOCAL WATER SAMPLING AND REPORT
Under supervision of school staff, students will extend their testing skills to measurements from water samples collected outdoors. With RoboAchiever’s home office located at Science Park in New Haven, we present here a pictorial map of Greater New Haven Area with prominent water bodies displayed. The choice of sites will be up
to the school and results reported and shared online with RoboAchiever’s provided reporting tools. The freely available Google Maps service can also be used to map other sites, including other geographical locations to which our iECOshare program extends.
GL0BE WORLDWIDE SCIENCE AND EDCUATION PROGRAM https://www.globe.gov/get-trained/protocol-etraining
Our program will culminate with an introduction of students to the formalized hydrosphere testing protocols of the Globe Worldwide Science and Education program, including means of electrical conductivity analysis.
ELECTRICAL CONDUCTIVITY Electrical conductivity measurements are include as part of the GLOBE hydrosphere study. Students learn to explain how changing environmental conditions will result in different measurements, and further study the use of a probe in collecting electrical conductivity measurements.
OTHER ENVIRONMENTAL TESTING PROTOCALS Students are futher exposed to the fuller range of environmental protocols managed by Globe to evaluate all aspects of our world environment: •
Atmosphere
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Biosphere
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Hydrosphere
•
Pedosphere (Soil)
Finally stuedents are introduced to the many regions of the world participating in the Globe data-share project, and review their findings for comparative study and analysis as all attempt to improve the world in which we live.