48 Safety Scaie Laboatry Experimerds for Chemistry for oday Scager EXPERIMENTAL PROCEDURE A. Solution Formation Solutions result when one or more substances, called solutes, are dissolved in another substance called the solvent. In liquid solutions, the solutes may be gases, liquids, or solids; the solvent is a liquid. Some solid solutes can be recovered from liquid solutions by evaporating away the solvent. In this part of the experiment, you will test solid sodium chloride before it is dissolved in water. You will also test it after it is dissolved and recovered by evaporating away the water used to dissolve it. You will use the test results to decide the type of change (physical or chemical) that takes place in sodium chloride when it is dissolved in water and recovered by evaporating away the water Procedure 1. Weigh out two samples of solid sodium chloride (NaCI) with masses of about 02 g. Put each sample into a separate, dry, small (10-cm) test tubes. 2. Test the sample in one tube as follows: Moisten the end of a clean glass stirring rod with distilled water. Dip the moist rod into the sample so that a few crystals of solid adhere to it. Put the stirring rod with salt crystals into the flame of your burner 3. Note and record in Table 4.1 (under the "Original Solid" heading) the color of the flame that results in Step 2. 4. Test the remaining solid in the test tube as follows. Add 20 drops of distilled water and agitate the tube until the solid dissolves completely. Add more water drops if needed to dissolve the solid. Add 2 drops of 0.1 M siülver nitrate solution (AgNOs) to the clear liquid in the test tube and agitate tomix. Record the results of this test under the "Original Solid" heading of Table4.1 5. Dissolve the second sample of sodium chloride in water by adding 20 drops of distilled water to the test tube containing the second sample of solid that you prepared in Step 1. Agitate the test tube to completely dissolve the solid. You have now changed the solid by dissolving it to form a solution. 6. Recover the dissolved solid from the solution by evaporating away the water. This can be done by tilting the test tube and gently heating it slightly above the liquid level, while gently agitating the tube to bring the liquid into contact with the hot portion. Figure 4.1 illustrates the technique, which will also be demonstrated by your instructor. Test tube Liquid holdor Burner Figure 4.1 Evaporation of iguids