Diet Coke & Mentos
by Keeley Tillotson, Anna Cincera and Stefanie Doughty
Table of Contents (for your navigational ease, clicky the linkys):
~*~ PURPOSE .:. HYPOTHESIS .:. METHOD .:. SET UP .:. RESULTS .:. RAW DATA .:. DISCUSSION .:. LINKS .:. RETURN TO RESEARCH PAGE ~*~
Top | Purpose:
The purpose of this experiment is to find out the relationship between the height of the spray of Diet Coke and the number of Mentos added.
Top | Hypothesis:
We believe that after a certain number of Mentos added, the spray height will cease to increase and will plateau at which point the amount of kinetic energy will also reach its peak. We believe that this will happen because at some point the addition of the Mentos will become inconsequential as there is not an unlimited amount of CO2 in the Diet Coke. The number of Mentos is the X variable and the height of the spray (defined by the distance in inches the Coke spout reaches above the bottle) is the Y variable. Kinetic Energy is defined as the energy of the spray’s upward motion.
Top | Method:
A meter stick was suspended directly above the rim of a 2 liter Diet Coke bottle. This was so we could measure the spray (in inches) once the Mentos were dropped into the soda. We constructed a paper funnel to drop the Mentos into, in order to make sure all the drops were uniform and that all the Mentos went in. We dropped the Mentos into the cola and, while filming the reaction, measure the spray height, using the meter stick. We started with 2 mentos, and then increased it to 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13.
Top | Set Up:
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Top | Results:
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Uncertainty: Approximately +/- .5 inches, due to human error. It proved difficult to name an exact measurement, so almost all measurements were estimated within .5 inches.
Top | Discussion:
In conclusion, our hypothesis was supported. The height of the spray increased gradually until we reached ten Mentos at which point the spray height reached its maximum at 65 inches (+/- .5 in.) and after that, ceased to increase. After a slight drop at eleven Mentos, it plateaued at a height of around 45 inches, just as we predicted it would. The fact that it plateaued after ten mentos means that the kinetic energy also plateaued at that point as the energy behind the spray obviously was no longer increasing. Just because ten mentos made the highest spray does not necessarily prove that 65 inches is the highest spray possible, in fact we know from looking at data from other similar experiments that the spray can reach far beyond 65 inches. For our experiment however, we found ten mentos to be the optimal number. We believe that if we used a more efficient method of adding the Mentos (such as stringing them on a wire and dropping them all in at once) would increase the height of the spray. We believe this because when using the funnel, only the first two or three mentos drop in before the reaction begins and the rest fall well after the CO2 bubbles begin to appear. We feel confident that a more violent reaction would have been produced if all ten mentos could react at once and would change our experiment to more efficiently add Mentos, were we to do it again. We would also do more trials to ensure accurate data (although in our first trial of this experiment, the peak was also reached at ten Mentos). Some websites also suggest that if you open the Coke bottle slower, less CO2 is initially released, and also suggests that freezing Mentos slows the initial reaction time allowing for more Mentos to enter the Coke. WHAT GREAT IDEAS OH MY GOD WHY DIDN’T WE THINK OF THESE?!
http://en.wikipedia.org/wiki/Diet_Coke_and_Mentos_eruption - Wikipedia article on Coke/Mentos Eruption. Somewhat limited in the scientific explanation department but will give you the general idea and the history behind the experiment.
http://www.newscientist.com/article/dn14114-science-of-mentosdiet-coke-explosions-explained.html - Tonya Coffey explains the difference in reactions (and the reasons for those reactions) between different types of Mentos/Sodas
http://eepybird.com/dcm1.html - Describes Coke and Mentos on a grand scale and includes examples of experiments that have been done
http://www.npr.org/templates/story/story.php?storyId=5341058 - Audio account from scientist about effects and results of reaction
http://www.zap2it.com/tv/news/zap-mythbustersmentos,0,4325641.story - Results from example experiment and information about technique