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Which Substance When Dissolved in Water will Conduct an Electrical Current?

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Author: Michael Calhoun

Safety: Do not ingest the substances used in this project

Some substances when dissolved in water to produce a solution will conduct an electrical current.  Such substances produce ions when dissolved in water, and it is the ions which carry the current through the solution. The research aspect of this science fair project is to use a conductivity device to determine if various substance dissolved in water can or cannot conduct electricity.

This science fair project focuses on the use a conductivity device that will enable the investigator to determine if a substance dissolved in water can or cannot conduct electricity and if it can, what type of conductor (electrolyte) it is.

From the observations made a data table will be generated and results displayed in the form of a graph.  

Materials and Equipment / Ingredients

Conductivity device, plastic cups, large paper clips, masking tape, distilled water, mineral water, table sugar, carbonated soda, table salt, and household vinegar. 

With the exception of the conductivity device all of the materials can be purchased from the local supermarket or major retail (Wal-Mart, Target, Dollar General, etc) discount department store. The Tri-fold display board can be purchased from an art & craft store.

A conductivity device can be purchased from the following online venders:

  • Science in a Bag Conductivity Circuit Board Indicator” retails for about $16.00 and includes free shipping.
  • ScienceKit, Inc “Audio/Visual Conductivity Indicator” Catalog # WW45354M50 retails for about $42.00 and sometimes offers free shipping and handling.  

Introduction

An electrical current results from the motion of electrically charged particles in response to forces that act on them from an applied electric field. Pure water is not a good conductor of electricity. Some substances when dissolved in water to produce a solution will conduct an electrical current.  Such substances produce ions (charged electrical particles) when dissolved in water and these ions carry the current through the solution. Solutions that contain this capability are called Electrolytes. Because the electrical current is transported by the ions in solution, the conductivity increases as the concentration of ions increases. Non-electrolytes are substance when place in water do not produce solutions that contain ions and hence do not conduct an electrical current. Electrolytes can be classified as either strong electrolytes or weak electrolytes depending on their ability to ionize completely or partially.  

Electrical conductivity can be measured using a conductivity measuring device consisting of two metal electrodes usually spaced 1 cm apart (thus the unit of measurement is microSeimens or milliSeimens per centimeter). A constant voltage is applied across the electrodes resulting in an electrical current flowing through the solution to be tested. Since the current flowing through the solution is proportional to the concentration of dissolved ions in the water, the electrical conductivity can be measured. The higher the dissolved ion concentration, the more conductive the sample and hence the higher the conductivity reading. 

A conductivity device is commonly used in hydroponics, aquaculture, swimming pools, and freshwater systems to monitor the amount of nutrients, salts or impurities in the water.

Digital photos can be taken during the experimenting process and the following websites offer down loadable images that can be used on the display board:

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