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SYLLABUS

Ionic compounds are composed of positive ions (i.e., cations) and negative ions (i.e., anions) that are bound together to form salts of net neutral charge. When ionic compounds are placed in water they tend to dissolve and form individual ions. So an ionic compound like sodium chloride (NaCl) becomes separate Na⁺ and Cl^- ions when dissolved in water. Therefore, when you add ionic compounds to water, you form an ionic solution. In the case of NaCl in water, the result is often called a “saline” solution.

Saline solutions are often given to patients in hospitals to hydrate (i.e., add water) them after an illness. These solutions are also important because the sodium ions and chloride ions (called electrolytes in medical terms) are used for many biochemical processes in the human body that require electrolytes to function properly. Salt solutions can also be called electrolyte solutions, because the ions in them are capable of conducting electricity. Electricity is simply the transfer of electrons through a conducting material. You are probably most familiar with metal wires conducting electricity, but many ionic solutions are capable of this transfer of electrons as well.

            In today’s lab we will be testing the conductivity (how well the saline solution conducts electricity) of saline solutions of different concentrations in order to determine the relationship between ion concentration and conductivity.

            You will create a series of NaCl solutions ranging from 5.0 M to 1.0 M and use a light circuit to determine if an increase in salt concentration increases or decreases the conductivity of a saline solution.  You will also be checking the conductivity of some common fruits and vegetables to see if they are capable of conducting electricity.