Science Buddies: "Ask an Expert"

In conducting this experiment, my son hypothesized that the hot tap water would create a quicker reaction time of the alka seltzer dissolving due to the increase in kinetic energy. He found this to be true after testing hot tap water, cold tap water, and ice water; however, when he decided to try it with boiling water, the reaction time was slower than regular hot tap water, but faster than the other temperatures. We aer unsure how he should explain this result. Please advise. Project is due Feb 6th

Hello,
The Alka-Seltzer website provides one answer to your question: http://www.alka-seltzer.com/asp/faqs.html#q15
If you saw that the tablet was floating at the top as the answer suggested, not all of the tablet's surface was in contact with the water and that explains the longer reaction time. Chemical reactions happen faster when there is more surface area in contact between the reactants.

Hi Snooper2U,

ChiaraB brings up a good point. I just want to add that you could even refer to the surface area explanation as a source of error since it led to an unintentional variable. The only variable you were testing, from what I read, was the temperature of the water, so be sure to clarify that!