Demonstrating Newton's third law which states that all forces between two objects exist in equal magnitude and opposite direction, the alka-seltzer rocket experiment aims to find the combination which propels the rocket the greatest distance.
The alka-seltzer rocket experiment demonstrates Newton's third law. In rocketry, a chemical reaction rapidly creates gas that is expelled in one direction from its container (the rocket engine); momentum forces the rocket in the opposite direction. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces. When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body. For example, students are sometimes asked to experiment with the amounts of water and Alka-Seltzer to find the combination which propels the rocket the greatest distance. 
