Should be based on observations made during the experiment. Evaluation of laboratory exercise type: On a separate page, each student should write a brief comment regarding 1) which lab method you prefer (inquiry-method, i. E. Problem-solving oriented, or traditional lab. Like this one. 2) group size (individual labs or small-group labs) 3) report writing – individual or small group 4) Any negative aspects about chem.. Lab & how we can improve them 5) any other comments We expect an evaluation from everyone. If you prefer not to put your name on this evaluation, that’s k.
Lab Instructions: Objectives: 1. To determine the boiling point of a liquid, and 2. To determine the melting point of a solid. Materials Used: Matches Spoilsport (Rubbing) Alcohol 1-2 small rubber bands Thermometer Powdered stand beaker 2 closed-end capillary tubes (melting point tubes) 10-12 mm diameter test tube Heat source Discussion and Review: In this experiment we will examine additional physical properties of liquids and solids. Two of the more important physical properties of pure substances are the boiling point and the melting point.
The boiling point of a liquid is the temperature at which that liquid is converted to a gaseous state. Boiling point is formally defined as the temperature at which the vapor pressure of the liquid becomes equal to the pressure at the surface of the liquid. The boiling point of. A liquid can change if the pressure at the liquid’s surface changes. Since pure substances have a distinct boiling point, boiling points are sometimes used to determine the purity of substances. The melting point is the temperature at which a solid is converted to liquid. This is an important property of solids.
What Is Papers Melting Point
The melting point of solids, like the boiling point of liquids, is often used for the identification of substances. Boiling points and melting points are recorded in the Handbook of Chemistry and Physics, and can be found in the sections titled ” Physical Constants of Organic Compounds” and ‘Physical Constants of Inorganic Compounds”. PROCEDURES: I. Boiling Point 1 . Make a test tube assembly by using the following directions and illustration. A. Place about 1 ml of Spoilsport alcohol in a 10-12 mm diameter test tube. B. 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. C. Insert an inverted closed end capillary tube into the test tube. . Make a water bath assembly by using the following directions and illustration. A. Half fill a 100 ml 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. ] b. 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. . 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 oils 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. ] d. Remove the heat source and begin observing the stream of bubbles. E. When the last bubble emerges from the capillary tube, record the temperature. 3.
Reheat the water bath and repeat the cooling process two more times. Record the temperature reading after each trial, and average all three trials. 4. The published boiling point of spoilsport alcohol is 82. Co. 5. Calculate the error between the observed boiling point and the published value of the boiling point. II. Melting Point 1 . A. Push the open end of a capillary tube into the powdered academic. B. Move the powder to the closed end of the capillary tube by tapping it on the table. Repeat until the the powdered academic occupies 1-2 mm of the capillary tube end. C.
With rubber bands, attach the capillary tube to a thermometer and align the bulb of the thermometer with the closed end of the capillary tube. D. Make a water bath as before by half filling a 100 ml beaker with warm tap water. E. Place the thermometer/capillary tube assembly in the water bath so that the surface level of the powdered academic is beneath the surface level of the water bath. F. Place the beaker on the burner stand and, stirring frequently to insure even heating, carefully heat the water bath with your heat source. G. Note the temperature at which the academic melts. Remove heat source. . Let the academic cool and recitalist. Repeat the procedure two more times and average the results. i. The published melting of academic is ICC. Compare your experimental result with the accepted (published) value. . Calculate the percent error. Clean-up: Dispose of the used capillary tubes by putting them in your trash can. If any spoilsport alcohol is left in your test tube, you may pour it down the drain with All contents copyrighted (c) 1 998 Peter Scoffing, Ph. D. , Professor of Science, Colorado Mountain College All Rights reserved Experiment 10 As described in the lab manual: 1.
Record the barometric pressure. 2. Measure about 10 Goff ice using the chemical balance and place it into a 100 ml beaker. Heat over a flame until half of the ice has melted. Remove from heat and measure the temperature s accurately as possible using your laboratory thermometer. Repeat with a 10. 0 g sample of your unknown. Be sure to record your unknown number. 3. Measure 50 ml of water using your graduated cylinder and pour it into a 200 ml beaker. Bring the liquid to a boil over a flame. After the liquid has been boiling for approximately 1-2 minutes, measure the temperature of the boiling liquid.
Repeat with a 10 g sample of your unknown. Record all data in your lab notebook and clean up. We followed all the steps above pretty much closely and pretty much got the results for water that we expected, except that the ductwork had cheap thermometers because one of them broke (this was my lab partner’s fault – she used it as a stirring rod which is exactly what you said not to do in your lecture) and the new one was off by a few degrees – but it was close enough for this simple experiment. The pressure in the room was 761. 2 and the temperatures we measured for our unknown were: -15 and 17.
Correcting for our water results this made our measurements -15. 2 and 17. 4 after the corrections. Based on these temperatures and the data we looked up in the library, our unknown was certainly “blabber gas. ” The error in our results as really small and the experiment worked really good. Other errors include: possible math errors in our calculations and human error. Overall the lab was really good and we learned quite a lot of stuff. Especially liked the part where the blabber gas exploded when heated scaring my partner (I think that may be why she broke the thermometer).
The only criticism of the lab is that the equipotent wasn’t really great and that we ran out of time but otherwise it was a really good experience and I think it taught us a lot of chemistry. Notes: For references we used our textbook, lab manual, and the Chemical Handbook mound on shelf 2 of the library (behind the reference desk). What to do? A. Student Chemistry 1 Identification of a Compound using Melting and Boiling Points Introduction One of the primary methods used to characterize a new compound is the physical determination of its normal melting and boiling points.
The “normal” melting and boiling point is the temperature at which a substance melts or boils when the barometric pressure is 760 mug or 1 ATM. In this experiment we will first calibrate our thermometers using ice and water, whose normal melting and boiling points are well characterized as 0. DC and 100. 0 ICC, respectively[l]. Following this, we will measure the normal melting and boiling points of an unknown compound. We will use this data to determine the identity of our unknown from a list of possible unknown samples and physical data from the Chemical Handbook.
Experimental Procedure As described in the lab manual, ice was placed in a beaker and warmed until approximately 50% had melted. The temperature of the ice/water mixture was then measured with a thermometer. This was followed by a similar measurement of our solid unknown. In part II, water was heated until boiling and the enrapture of the liquid/gas mixture measured with a thermometer. This was followed by a similar measurement using our unknown compound. Toggle the best results possible, the procedure in the manual was modified by repeating each trial three times.