PROCEDURE Part A: Fill a 600 mL beaker about halfway with ice. Add a small amount of water (about 50 mL) and then add rock (coarse) salt until some salt remains undissolved on the bottom of the beaker. Stir and keep stirring. Measure and record the temperature of the ice-salt solution at 5 minutes, 10 minutes, 15 minutes, and 20 minutes. The temperature should drop to at least -10°C. If it does not, consult your instructor. Keep the mixture for parts B and C. Part B: Before doing this part, you will need to pour out some of the water from the ice bath, then add more ice and more rock salt to the beaker. If the ice bath is not cold enough, this part and part C will not work. Put about 25 mL of deionized water in a large test tube. Place the test tube in the beaker with the salt/ice/water mixture from Part A so that the water in the tube is below the level of the salt/ice/water mixture. You may clamp the test tube to a ring stand or someone can hold it using a test tube holder. Measure and record the temperature of the water in the tube every minute for 15 minutes or until the temperature is constant for at least two minutes. Stir the water in the beaker from time to time. NOTE: If your instructor so directs, you may use the Vernier equipment and LoggerPro to generate a graph of temperature versus time to determine the freezing point. Part C: Again, you will need to pour out most of the water, then add more ice and more rock salt. Weigh about 25 grams of deionized water (be sure to record the mass) and place it in a large test tube. Add 1.0-3.0 grams of crystalline sodium chloride (not rock salt) to the water and stir until the salt dissolves. Place the test tube in the beaker with the salt/ice/water mixture, making sure the level of liquid in the test tube is below the level of liquid in the beaker. As in part B, measure and record the temperature of the water in the tube every 60 seconds (beginning at zero seconds) for 15 minutes or until the temperature levels off. The Vernier equipment may be used if your instructor directs.