Also, to increase the efficiency of the device, we insulated the beaker of yeast with cotton and styrene foam so the maximum heat will be applied to the thermometer, an aspect of Physics. This is important because the greater the temperature rise, the more accurate the approximation. We considered placing the beaker of yeast into a styrene foam container to maximise the temperature rise but unfortunately, could not find any suitable containers so this was eluded.
Materials:
±0.0001˚C±2%
180mL
20mL
1.00g
4000.0±0.1g±2%
100±1mL
100.0±0.5˚C
400mL
600mL
temperature sensor
water
hydrogen peroxide
yeast
balance
measuring cylinder
alcohol thermometer
beaker
beaker
cotton and styrene foam for insulation
Procedures for Measuring Time:
- Measure yeast and place into 400mL beaker.
- Wrap 400mL beaker with cotton and place into 600mL beaker.
- Poke a hole into the centre of styrene foam and place thermometer through it.
- Measure water and hydrogen peroxide.
- Pour water and hydrogen peroxide into 400mL beaker and place the foam lid on the beaker when music begins.
- Note the temperature when music ends and approximate the time from standard curve (blue line on graph 3, attached to this document).
Conclusion and Evaluation:
Although the results were fairly accurate during calibration, when it came to the actual measurement of time, the results were off by 1 minute. The average temperature of yeast when the music ended was 37.8˚C which gives 176 seconds, or 2 minutes 56 seconds, but the length of music was in fact 3 minutes 55.95 seconds, almost exactly I minute longer than the estimated time.
As this device relied heavily on biological process of yeast, it is quite unpredictable and extremely sensitive to change in environment, so the results were not very surprising. In fact, we had realised after moving the device from the Biology laboratory to the Chemistry laboratory that the last minute calibrations came out lower than the standard curve we started with (purple in on graph 3) showing the instability of the device.
In the Biology laboratory, experiments were repeated at the corner of the room where there was least air conditioning so that there will be the least effect of cool air flow on the fermentation of yeast. Also, the temperature of tap water was slightly warmer, and there was more sunlight in the Biology laboratory, which may have been another reason why the temperature rise was greater there than in the Chemistry laboratory.
After further calibrations in the Chemistry laboratory, the standard curve had to be lowered from the purple to the blue line on graph 3, but occasionally, the results came to the green line as well. Then, the materials were left in the laboratory for one hour under fairly strong air conditioning which cooled the yeast, water and hydrogen peroxide, which was perhaps the greatest cause of the even slower rate of temperature rise during the actual time measurement.
To keep the results consistent, the music may have had to be measured in the Biology laboratory where the device was originally calibrated, or the device should have been calibrated in the Chemistry laboratory. Also, the container of yeast needed better insulation, which could be improved by using a vacuum flask like those used for water bottles. The water and hydrogen peroxide used could also be placed separately in similar flasks so that there will be minimal influence from the environment.
Overall, this project was a very good opportunity to share, apply and develop our knowledge on our Group 4 subjects. It was very challenging to have to consider applying all three sciences into one device, even more so to make it measure with accuracy. Finally, the project has enhanced our awareness to the many elements influencing our experiments that we must take into greater consideration.
