Melting point and Boiling point determination
Aim: To determine the boiling point of a liquid and to determine the melting point of a solid.
Apparatus: Matches, Isopropyl (Rubbing) Alcohol, 1-2 small rubber bands, Thermometer, Powdered Acetamide beaker, 2 closed-end capillary tubes (melting point tubes), 10-12 mm diameter test tube, Heat source.
Safety: Safety glasses and lab coat must be worn at all times while carrying out the experiment.
1. Place about 1ml of Isopropyl alcohol in a 10-12 mm diameter test tube.
2. Using a small rubber band, attach a thermometer to the outside of the test tube. The thermometer bulb should be even with the test tube's bottom.
3. Insert an inverted closed end capillary tube into the test tube.
4. Make a water bath half fill a 100ml or larger beaker with warm tap water. [Note: a water bath is used if the boiling point of the material is expected to be less than the boiling point of water; otherwise, an oil bath is needed.]
5. Place the above test tube assembly in the water bath so that the surface level of the alcohol in the test tube is beneath the surface level of the water bath.
6. Place the beaker on the wire stand and, stirring frequently to insure even heating, carefully heat the water bath with your heat source until the water bath boils and a rapid stream of bubbles continuously emerges from the capillary tube. [Note: if an oil bath is used, the oil does not boil; the stream of bubbles from the capillary tube is the sole indicator that the liquid in the pipette or test tube is boiling.]
7. Remove the heat source and begin observing the stream of bubbles.
8. When the last bubble emerges from the capillary tube, record the temperature.
9. Reheat the water bath and repeat the cooling process two more times. Record the temperature reading after each trial, and average all three trials.
10. The published boiling point of isopropyl alcohol is 82.4 oC.
11. Calculate the error between the...