Conducting Solutions

Recommended for grades 6–12.

Figure from experiment 4 from Agricultural Science with Vernier

Introduction

In this experiment, you will study the electrical conductivity of water and various water solutions. A solution can contain molecules, ions, or both. Some substances, such as sucrose (C₁₂H₂₂O₁₁) and glucose (C₆H₁₂O₆), dissolve to give a solution containing mostly molecules. An equation representing the dissolving of sucrose (table sugar) in water is:

${{\text{C}}_{{\text{12}}}}{{\text{H}}_{{\text{22}}}}{{\text{O}}_{{\text{11}}}}{\text{(s)}} \leftrightarrow {{\text{C}}_{{\text{12}}}}{{\text{H}}_{{\text{22}}}}{{\text{O}}_{{\text{11}}}}{\text{(aq)}}$

where (s) refers to a solid substance and (aq) refers to a substance dissolved in water. Other substances, such as calcium chloride (CaCl₂), dissolve in water to produce a solution containing mostly ions. An equation is:

${\text{CaC}}{{\text{l}}_{\text{2}}}{\text{(s)}} \leftrightarrow {\text{C}}{{\text{a}}^{{\text{2 + }}}}{\text{(aq) + 2C}}{{\text{l}}^{\text{ - }}}{\text{(aq)}}$

Calcium ions are necessary for muscle contraction, mitochondrial activity, bone formation, and many other metabolic processes. Organisms may obtain minerals such as calcium from their water supply, since ions dissolve in water.

You will determine conductivity of the solutions using a computer-interfaced Conductivity Probe. The unit of conductivity in this experiment is microsiemens per centimeter, or µS/cm.

Objectives

In this experiment, you will

Write equations for the dissolving of substances in water.
Use a Conductivity Probe to test the electrical conductivity of solutions.
Determine whether molecules or ions are responsible for electrical conductivity of solutions.

Sensors and Equipment

This experiment requires each of the following Vernier sensors and equipment (unless otherwise noted):

Conductivity Probe

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Download Experiment Preview

The student-version preview includes:

Step-by-step instructions for computer-based data collection
List of materials and equipment

Note: The experiment preview of the computer edition does not include essential teacher information, safety tips, or sample data. Instructions for Logger Pro and other software (such as LabQuest App or TI handheld software, where available) are on the CD that accompanies the book. We strongly recommend that you purchase the book before performing experiments.

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Standards Correlations

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