~The properties of electrolytes depend upon the ions present.~ When a substance capable of dissociating into ions is dissolved in water, the properties of the solution will depend upon two factors: (1) the ions formed from the substance; (2) the undissociated molecules. Since the ions are usually more active chemically than the molecules, most of the chemical properties of an electrolyte are due to the ions rather than to the molecules. The solutions of any two substances which give the same ion will have certain properties in common. Thus all solutions containing the copper ion (Cu^{++}) are blue, unless the color is modified by the presence of ions or molecules having some other color. EXERCISES 1. Distinguish clearly between the following terms: electrolysis, electrolyte, electrolytic dissociation, ions, solute, solvent, solution, saturated solution, and supersaturated solution. 2. Why does the water from some natural springs effervesce? 3. (a) Why does not the water of the ocean freeze? (b) Why will ice and salt produce a lower temperature than ice alone? 4. Why does shaking or stirring make a solid dissolve more rapidly in a liquid? 5. By experiment it was found that a certain volume of water was saturated at 100 deg. with 114 g. of potassium nitrate. On cooling to 0 deg. a portion of the substance crystallized. (a) How many grams of the substance remained in solution? (b) What was the strength of the solution at 18 deg.? (c) How much water had been used in the experiment? 6. (a) 10 g. of common salt were dissolved in water and the solution evaporated to dryness; what weight of solid was left? (b) 10 g. of zinc were dissolved in hydrochloric acid and the solution evaporated to dryness; what weight of solid was left? 7. Account for the fact that sugar sometimes deposits from molasses, even when no evaporation has taken place. 8. (a) From the standpoint of the theory of electrolytic dissociation, write the simple equation for a dilute solution of copper sulphate (CuSO_{4}); this solution is blue. (b) In the same manner, write one for sodium sulphate; this solution is colorless. (c) How would you account for the color of the copper sulphate solution? 9. (a) As in the preceding exercise, write a simple equation for a dilute solution of copper chloride (CuCl_{2}); this solution is blue. (b) In the same manner, write one for sodium chloride; this solution is colorless. To what is the blue color due? 10. What component is present in concentrated sulphuric acid that is almost wanting in very dilute sulphuric acid? 11. Why will vegetables cook faster when boiled in strong salt water than when boiled in pure water? 12. How do you explain the foaming of soda water? CHAPTER X ACIDS, BASES, AND SALTS; NEUTRALIZATION