Monday, April 9, 2018

Alka Seltzer Blast-off 2

This project effectively demonstrates the Newton's Laws of Motion.




First Newton's Law of Motion states that an object either remains at rest or continues to move at a constant velocity unless a force acts on it.

  • The rocket is at rest, but when it's acted upon by the chemical reactions of water and the Alka-Seltzer tablets, it has a powerful lift-off. The force of the reaction blows off the film canister lid.

Second Newton's Law of Motion states that Force is equal to mass multiplied by acceleration.

  • Force = mass x acceleration
  • The force of that lift-off is equal to the mass of the film canister, the water, and the tablet inside multiplied by the acceleration provided by the chemical reaction.

Third Newton's Law of Motion states for every action, there is an equal and opposite re-action.

  • As the film canister lifts off, the canister lid, water, gas, and slide experience the downward force of the push. The lid pops off. The water and the gas spread out, but because the slide is secured on the ground, we can't see it move.




The Chemistry behind the project:

  1. Alka-Seltzer tablets contain sodium bicarbonate and citric acid.
  2. When the Alka-Seltzer tablet piece comes in contact with the water inside the film canister, it begins to dissolve. 
  3. This results in sodium citrate, water, and carbon dioxide gas.
  4. The carbon dioxide gas builds the pressure inside the film canister.
  5. Eventually, the pressure inside will pop the film canister lid off.

H3C6H5O7 + NaHCO3  ==========>  NaC6H5O7 + H2O + CO2 + Heat

Citric Acid + Sodium Bicarbonate ========> Sodium Citrate + Water + Carbon Dioxide + Heat


Because Heat is released during the process, this chemical reaction is called an 
exothermic reaction.


Second Newton's Laws of Motion states F = ma. So, different amount of water or Alka-Seltzer piece will affect the take-off time and altitude of our rocket.

Also, take-off time is affected by the surface area of Alka-Seltzer exposed to water. Crushing it will reduce the take-off time significantly.



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