The Many Uses of Alka-Seltzer

I have never used Alka-Seltzer for its intended medicinal purpose.  Not even one time.

I have, however, found it to be an important classroom resource, one every homeschool teacher needs to have on hand for science.

Last spring, we made rockets using alka-seltzer tablets for our "fuel" and this was one of the most popular science demonstrations I did at co-op class, and provided lots of free-time entertainment at home as well.  I don't know that I have pictures of it - I will have to check.  The basic idea is to construct a paper rocket around an empty 35mm film canister - the kind with the pop-off lid that fits inside the rim rather than outside, if that makes sense.  Then you fill the canister about 1/3 with water, drop in an alka-seltzer tablet that's broken up a bit, put the lid on, and then set the rocket down upright and begin your countdown.  You have to work pretty quickly, but it's easy!

This week we did some science demonstrations testing the reaction rate of alka-seltzer tablets in water when certain variables were changed.  First, we tested the effects of temperature on reaction rate.  We dropped alka-seltzer tablets into water at three temperatures - nearly boiling, lukewarm, and ice cold - and timed how long it took for each to completely dissolve.  (It dissolved fastest in the hot water, and slowest in the cold)  In the second activity, we tested the effects of surface area on reaction rate.  We timed how long it took for a tablet to dissolve completely in water.  We did it three times - with a whole tablet, a tablet broken into about four or five pieces, and a tablet crushed into mostly powder.  (The powder dissolved fastest, the whole tablet slowest)