Timing a Chemical Reaction with Alka-Seltzer (SOL 5.1)

Observe Alka-Seltzer dissolve and note the end of a chemical reaction

SOL: 5.1

The student will conduct investigations in which

appropriate instruments are selected and used for making quantitative observations of length, mass, volume, and elapsed time;
rocks, minerals, and organisms are identified using a classification key;
data are collected, recorded, and reported using the appropriate graphical representation (graphs, charts, diagrams);
accurate measurements are made using basic tools (thermometer, meter stick, balance, graduated cylinder);
predictions are made using patterns, and simple graphical data are extrapolated; and
estimations of length, mass, and volume are made.





soda bottle
measuring cup (1 cup)
long tube (20 inch piece of aquarium tubing works well)
1 Alka-Seltzer tablet
science journal


Pour 1/4 cup of water into the soda bottle. Squeeze the clay around the tubing so that the top of the bottle can be air tight when the tubing is inserted. Fill the jar with water. Place the free end of the tube in the water. Drop an Alka-Seltzer tablet in the soda bottle and quickly seal off the top with the clay and tube. Note the time. When all of the bubbling stops, record the time again.

The tablet should be fully dissolved in about 25 minutes.


The dry acid and baking soda in the tablet are able to combine with the water to form carbon dioxide gas. It is the carbon dioxide gas that moves through the tube and forms bubbles in the glass of water. The bubbling stops when all the material has reacted.

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