Demonstrations
A rubber rod is given an electrostatic charge by rubbing it briskly with a cloth. As the rod is brought up to the stream of water from a buret, the water is attracted to the charge because of the attraction of the dipoles for the charge on the rod.
The solution contains more sodium acetate than a saturated solution at room temperature. It is, therefore, not at equilibrium. When a crystal of sodium acetate is added to the solution, it immediately induces crystallization, which then continues until a saturated solution is attained.
The temperature of the solution decreases about four degrees as ammonium nitrate is added is added to the water. Thus, the dissolution of ammonium nitrate is endothermic.
The temperature of the solution increases by almost a degree when a small amount of ferric nitrate is added. The dissolution of ferric nitrate is therefore exothermic.
The electrodes (held in the pen-like device) are attached to a source of direct current. A multimeter, operating in the ammeter mode, is connected as shown in the text. The meter readings are in milliamps. In the first part of the demonstration, the conductivity of distilled water is determined to be very small--a meter reading of close to zero milliamps is obtained. Then pure acetic acid is added by pipet to the water and about eight milliamps of current flow through the solution. In the last part of the demonstration, a beaker of 3 molar hydrochloric acid is tested and found to conduct about 16 milliamps of current. The greater conductivity of the hydrochloric acid is due to the fact that it produces a greater number of ions in solution.