Letter of Transmittal. Dr. Henry:

Transcription

1 Letter of Transmittal Dr. Henry: Enclosed are the research results for experiments conducted to observe the reaction times of the three denture tablet brands: Effervescent, Efferdent, and Polident. The three brands were tested at four different temperatures (in an ice bath, room temperature, 38 C, and 50 C) in 120 ml of water. Additionally, the Effervescent tablets reaction times were observed for varying physical states, water concentration, applied forces, and with two tablets at once; these extra experiments were done to observe how a changing environment would affect the reaction time. Out of curiosity, one trial was also conducted with a foreign brand of denture tablets.

2 Adventures with Dentures The University of Tennessee at Chattanooga Chemical Engineering 4350 Lab Sarah Torgeson and Becca Palmer Instructor: Dr. Jim Henry 27 September 2011

3 Abstract: The purpose of this experiment was to observe how environment variances influence the reaction time of different denture cleaners. Temperature was the main factor tested, but water concentration, the physical state of the tablets, subjecting the solution to stirring and agitation, and the number of tablets reacting were also observed. One foreign denture tablet was also observed at normal conditions. The tablets were introduced to four different temperatures and the reaction times were tested for each. One brand, Effervescent, was tested at the variety of states previously mentioned to determine their effect on reaction time. The different temperatures were controlled using a Polystat Immersion Circulator and the temperatures of the beakers were monitored during the reaction to insure greater accuracy. The tablets were found to react faster at higher temperatures, and Effervescent was found to react the fastest out of all the brands. All the reactions, except for the Irish tablets, were found to be exothermic and the temperature of the environment rose as the reaction continued towards completion. The more variability in the environment and physical state of the tablet, the faster the tablets were found to react.

4 Table of Contents: I. Introduction II. Theory III. Equipment A. Description of equipment B. Pictures of used equipment IV. Procedure V. Results VI. Discussion of Results VII. Conclusion VIII. Recommendations IX. Appendices A. Raw data

5 Introduction: Effervescing tablets are used with water in order to clean retainers and dentures. The tablet is put in water and is generally left to clean the retainer or denture overnight. The point of this experiment is to determine the affect of temperature, water concentration, and stirring/agitation on the reaction time of three different denture tablet brands. Theory: In most cases, reaction times will speed up with increased temperature and solvent concentration. Therefore, it is expected that the reaction times for all three tablets will decrease as they react in warmer water. Diffusion is the spread of molecules from areas of high concentration to areas of low concentration. When the tablets react with water, the molecules from the tablets attempt to spread to the area of low concentration (the water) until the beaker is in equilibrium. Therefore, as the level of water the tablet reacts in increases, it is anticipated that the tablets will react faster to equalize the beaker. As the reaction time of the tablets increases, it is assumed that the reaction will slow down. With added stirring and agitation, the reaction will be expected to increase. Equipment: The equipment used during this experiment included three 200 ml beakers, four different types of effervescing tablets, three thermometers, a polystat immersion circulator, which can be seen below in Figure 1, and the tank that was used to hold the water bath, seen in Figure 2. Figure 1. Polystat Immersion Calculator

6 Figure 2. Experiment run with water bath for temperature control. Procedure: Part I Fill three 200 ml beakers up with 120 ml of water. Pick three tablets of the same brand to test, and make sure that they fit inside the opening of the beaker or flask without needing to be broken. (Do not take the tablets out of their packets until the water is ready, as they will react with the humidity in the air and decrease the fidelity of that experiment.) When the water reaches room temperature, record that temperature, and drop one tablet into each of the beakers simultaneously with starting the stopwatch. Take care to not agitate the solutions over the course of the reaction. Record the temperature change of each tablet at 60-second intervals. Record the ending time and temperature of each tablet when it has dissolved completely. Repeat the room-temperature procedure for each brand. Repeat the above procedure for each individual brand in an ice bath, 38 C bath, and 50 C bath. Use a Polystat immersion circulator to maintain consistent temperatures. This should result in temperature change data for a total of 36 individual tablets. After these experiments are complete, look at the data and pick a brand that provides consistent reaction behavior between individual tablets. That brand should be used during the second part of the experiment.

7 Part II Using that one brand, test the reaction times of the denture tablets at room temperature with the following variations: One tablet in 30mL water One tablet in 60mL water One tablet, crushed inside its pouch (so it will not react with the humidity in the air) in 120mL water Two tablets in 120mL water One tablet in 120mL water, stirring continuously One tablet in 120mL water, agitating continuously Record the temperature changes throughout the reaction in the same manner as Part I. Results: Graphs 1-3 show the reaction times of the different denture tablets at different temperatures. Figure 3. Polident Tablets Reaction Time

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9 Figure 4. Effervescent Tablets Reaction Time Figure 5. Efferdent Tablets Reaction Time Graph 4 compares all three of the denture tablets and their average reaction times at different temperatures.

10 Figure 6. RxN Length at Varying Temperatures Graph 5 shows how the Irish denture tablets compare to the other tablets reaction times at room temperature. Figure 7. Room Temp Tablet Variances Graph 6 shows the reaction times of the effervescent tablets in different environments and physical states. The reactions all occur at similar temperatures.

11 Figure 8. Effervescent Tablets Variants Discussion of Results: As predicted, all of the tablets were found to react faster with increased temperatures. The only exception was that Polident reacted faster in the ice bath than at room temperature. This could be due to human error (not documenting the right reaction time), or it could be the manufacturer s intended design to decrease reaction time under colder conditions to make the product more marketable to those who live in colder climates. Effervescent tablets were found to react the fastest at all room temperatures. Efferdent s reaction time was decreased by nearly half each time the temperature was increased. Polident was found to react the slowest, except for its reaction time in the ice bath. Irish denture tablets were tested to see how similar they were to the three American brands. At room temperature, the tablets were found to react at about the same time as the Efferdent tablets, however, the Irish tablets were different from all the tablets in that they were found to be endothermic and the temperature of the water decreased with time. All of the other tablets temperature increased as the reaction progressed and were found to be exothermic. The Effervescent tablets were found to react the fastest when the tablet was crushed. The crushed tablet was found to completely react in less than half of the time of the other varied conditions. This is most likely due to the fact that a crushed tablet will have more surface area with which to react in the water. The reaction times of the different water concentrations were found to be the same, but the temperature of the beaker with the 30 ml of water was found to jump almost 3 C in five minutes. This temperature jump is significantly greater than any of the other reactions. This implies that the tablets contain a exothermic limiting reactant, and it is likely that a higher percent of the water in solution was able to react. Conclusion:

12 Temperature was found to increase the rate of reaction in the denture tablets tested; as the temperature increased, the reaction time decreased. Water concentration was found to have an effect on the reaction time and the reaction time was found to be half of the time of the normal, 120 ml beaker of water. The agitated tablet was found to react faster than the stirred tablet. All of the varied Effervescent tests were found to react more than the normal, untouched tablets. Recommendations: In order to improve the experiment we would suggest having six more thermometers and attempting to test all of the denture tablets at once for each temperature chosen. By doing this we can insure that all of the tablets were tested under the same conditions and the data collected will have less variance.

13 Appendices: Raw Data:

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