Online Chemistry Experiments SUNYITCONF

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Information about Online Chemistry Experiments SUNYITCONF

Published on February 7, 2008

Author: Obama


Online Chemistry Experiments: Online Chemistry Experiments Venkat Chebolu, Ph. D. Associate Professor of Chemistry Jefferson Community College Watertown, NY 13601 List of Experiments: List of Experiments Observations of Chemical Changes Laboratory Techniques and Measurements Separation of a Mixture of Solids Properties of Gases Liquids and Solids Physical and Chemical Properties Ionic Reactions List of Experiments (contd.): List of Experiments (contd.) Stoichiometry of a Precipitation Reaction Caloric Content of Food Determination of Water Hardness Le Chatelier’s Principle Observations of Chemical Changes: Observations of Chemical Changes NaHCO3 + HCl HCl + Bromothymol Blue (BTB) NH3 + BTB NaOCl + KI observe and test with starch KI + Pb(NO3)2 NaOH + Phenolphthalein HCl + Phenolphthalein CuSO4 + NH3 Laboratory Techniques and Measurements: Laboratory Techniques and Measurements Length of various objects Temperature of boiling water and ice-water mixture Volume of water in a graduated cylinder Number of drops of water from a micropipet in 1 mL (graduated cylinder) Mass measured to 0.1g on a digital scale Density of liquids and solutions Laboratory Techniques and Measurements (contd.): Laboratory Techniques and Measurements (contd.) Density of Solid by Water Displacement Density of Solid by Archimedes’ Principle Separation of a Mixture of Solids: Separation of a Mixture of Solids Mixture of Iron Filings, Sand, Benzoic Acid and Salt Iron filings separated by using a magnet Sand separated by dissolving the Benzoic Acid and salt in hot water Benzoic Acid separated by cooling in an ice-bath and filtration of resulting crystals Salt isolated by evaporation of salt solution (filtrate) at room temperature Properties of Gases: Properties of Gases Gas is collected by displacement of water in a pipet bulb. H2 is generated by reacting (1)Zn and (2)Mg with HCl. O2 is generated from H2O2 and MnO2 CO2 is generated from NaHCO3 and HCl H2 is tested by blowing it over a lit match Properties of Gases (contd.): Properties of Gases (contd.) O2 is tested by inserting a lit toothpick into the pipet bulb Mixture of H2 and O2 collected in a pipet bulb is tested with a lit match as well CO2 is tested with lime water and with BTB and with a lit toothpick Gas evolved when Alka-Seltzer is dissolved in water is tested just like CO2 Liquids and Solids: Liquids and Solids B.P. of isopropyl alcohol is determined by inverting a closed-end capillary tube into 1 ml of the alcohol in a test tube. M.P. of acetamide is determined by filling a closed-end capillary tube with the solid and noting the temperature of the water bath when the solid melts. Physical and Chemical Properties: Physical and Chemical Properties Substances tested include Mg, Cu, Zn, MgO, CuCO3, Cu(NO3)2 and NaCl Tests include Color Odor Effect of heating in a test tube Solubility in Cold and Hot water, and litmus test Reaction with dilute HCl Reaction with dilute NaOH Ionic Reactions: Ionic Reactions In plate wells, each of the aqueous solutions of Co(NO3)2, Cu(NO3)2, Fe(NO3)2, Ba(NO3)2, and Ni(NO3)2 are reacted separately with solutions of Na3PO4, NaHCO3, NaI, Na2SO4, NaCl, Na2CO3 and NaOH Evidence of Chemical reaction is to be noted Net ionic equations to be written for chemical reactions occurring Stoichiometry of a Precipitation Reaction: Stoichiometry of a Precipitation Reaction Aqueous solutions of Na2CO3 and CaCl2.2H2O in a 1:1 molar ratio are reacted and the resulting precipitate of CaCO3 is collected quantitatively. Caloric Content of Food: Caloric Content of Food Food items such as Marshmallow, Peanut, Popcorn, Potato chip and Walnut are burnt, and the heat generated is used to heat a known mass of water in a beaker Heat generated per gram of each item burnt is calculated Determination of Water Hardness: Determination of Water Hardness Calmagite indicator is used to detect presence (red) or absence (blue) of Ca+2 and Mg+2 in water samples. In a plate well, calmagite is added to water samples of known and unknown hardness. The number of drops of EDTA needed to turn the solution blue in each case is determined. Le Chatelier’s Principle: Le Chatelier’s Principle Mg(OH)2  Mg+2 + 2 OH-1 In a plate well, an aqueous solution of MgCl2, to which phenolphthalein is added, is treated with an aqueous solution of NaOH till the solution turns pink. Then, HCl is added till the solution turns colorless. A part of this solution is sucked into a pipet bulb and held in cold and hot water to see how temperature affects this equilibrium. Le Chatelier’s Principle (contd.): Le Chatelier’s Principle (contd.) HSO4-1 + H2O  H3O+ + SO42- Thymol blue is used as an indicator to decide where the equilibrium lies. Na2SO4 and NaHSO4 are added successively to an aqueous solution of NaHSO4 to determine direction of equilibrium shift. This solution is placed in a pipet bulb and placed in hot and cold water baths to determine the effect of temperature on this equilibrium Differences: Differences Filter funnel supported in a paper cup placed in a coffee cup Rubber policeman at the end of the glass rod to wash down precipitates stuck to the walls of the containers not used Cutting, bending and drawing glass experiment not being performed online. Bunsen Burner and Fisher burner experience missing Differences (contd.): Differences (contd.) Inserting glass tubing into tygon tubing is not experienced online No experience using a triple beam balance Spectroline pipet filler not used online No experience with coffee cup calorimetry No sublimation of Naphthalene online No experience with simple distillation Differences (contd.): Differences (contd.) No experience with vacuum (Buchner funnel) filtration No experience with gravimetric experiments using crucibles and crucible tongs and heating to constant mass Charles law verification experiment not done online Determining solubility of a salt in water and determining whether a solution conducts electricity Differences (contd.): Differences (contd.) Factors affecting reaction rates lab is not done online Mg is dropped into different strong and weak acids of the same concentration Zn, Mg and Cu are dropped into solutions of HCl Iodine clock reaction rate is studied as a function of reactant concentrations Crushed and uncrushed marble is reacted separately with HCl Zn is added to HCl at different temperatures Differences (contd.): Differences (contd.) In F2F setting, there is a three hour time limit for the lab. Some students do feel pressured to complete the lab in that time or to come back later to complete the lab. In the online format, there is really no time limit and everyone works at their own pace resulting in observations such as the following: An unidentified aroma was evident during the entire separation experiment. The benzoic acid crystal formations seemed quite intriguing that resembled pieces of cut fiberglass or MSG. Very reflective and lustrous, but seemed to attach itself to other substances pretty easily. Salt crystal formation gathered to several clumps instead of an even formation at the cup’s bottom. Differences (contd.): Differences (contd.) In the F2F situation writing a lab report usually entails filling in the blanks or boxes in a pre-organized lab format that accompanies each lab followed by answering post laboratory questions. A lot of the answers received are very similar as they are provided after consultation with class peers. In the online format, the lab write-up is expected to include Title, Purpose, Procedure, Data Tables, Observations, Questions and Conclusions. The organization of the Data Tables and Observations is for the most part left for the students to figure out. Differences (contd.): Differences (contd.) In the F2F situation, when a single answer is proposed for a question, that answer is usually embraced by the rest of the class and no more thinking occurs without intervention. In the online mode, everyone is thinking on their own until they find some answer to the question. This results in a diversity of answers as evidenced by the following example. Differences (contd.): Differences (contd.) Answers provided for why the boiling point of water observed is different from 1000C: My water boiled at the expected temperature - perhaps this is an experimental error on my behalf The material of the pan that I boiled the water in may have had an effect on the boiling point of water. Also, the thermometer could be a little off The water boiled at a different temperature because the water was in a smaller container and the heat was directly applied Observations: Observations No instructor intervention after experiment is started. Students are forced to get creative. When graded lab report is returned, students’ understanding of the situation is much better because they have invested their best thinking into the problem. A sense of discovery takes hold of the students, especially when they seemed to have followed the procedure and what they see is different from what they expect. Observations (contd.): Observations (contd.) Repeating a lab after they have messed up is very rarely possible. Through these labs students are certainly getting a very good hands on experience in manipulating chemicals and honing their observation skills. This is very similar to the experience a student gets in a face-to-face lab course. Student Reactions: Student Reactions While performing this (Ionic reactions lab) I learned how to recognize ionic reactions and see when they can occur by mixing different substances. I enjoyed performing this experiment and my confidence of working in the laboratory has improved Student Reactions (contd.): Student Reactions (contd.) This lab demonstrates that there are many different ways to detect ionic reactions. These reactions become visible to the chemist as a color change, precipitate, or release of gas. It is very interesting to note how the exchange of positive and negative ions in two reacting solutions will change the solubility of a chemical and form a precipitate Student Reactions (contd.): Student Reactions (contd.) I found this (Caloric Content of Food) lab to be very interesting. I never knew it was possible to determine the energy content of a food item by burning it until I completed this experiment. Although I did find that particularly the marshmallow in this experiment lit on fire quickly and in a matter of seconds the flame became a bit out of control, so just a fore warning to those who have not completed the lab yet. Student Reactions (contd.): Student Reactions (contd.) This lab (Caloric Content of Food) has taught the process of finding the energy content of food by burning a portion of a certain food and taking the heat given off by the food and adding it to a known mass of water. My observations have also taught me that a longer burning food will probably lead to a higher caloric food, based on the peanut burning longer than the marshmallow. Student Reactions (contd.): Student Reactions (contd.) I found this (Water hardness) experiment very interesting. I especially enjoyed the fact that this is chemistry that I can in fact relate to in my every day life. Every one needs water to survive. I did find it quite awkward to stir the solution with a toothpick. However, in determining the water hardness of my local water it has made me consider the possibility of investing in a water softener. I am confident in my skills now and know that if I desire I can now test the local water supply wherever I go. Student Reactions (contd.): Student Reactions (contd.) This lab (Water hardness) was very interesting. The water in the area where I tested has always been a concern of mine. For me it was and still is very hard to get used to, the quality affecting everything from my food to my shower. In passing I have heard others say that water was hard but it was nice to actually test it and have proof of how hard the water actually was. Conclusion: Conclusion The kit is certainly helping students get the kind of hands-on experience that a F2F Chemistry lab provides. While certainly not providing each and every technique, these experiments go a long way in providing a medium for the students to get a first hand experience of learning Chemistry by doing. Further, it does provide a medium for students to think about the experiment they are performing and draw conclusions as in a regular brick and mortar Chemistry Lab. Acknowledgements: Acknowledgements Ron Krempasky AHS for this opportunity Linda Jeschofnig AHS for abstract writing Peter Jeschofnig AHS for co-presenting Vela Chebolu WHS for Powerpoint Design

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