Alka Seltzer Rocket Activity

I recently shared the idea of this rocket with another Instructables member.  So I thought it was about time I wrote it up.  I remember the first time I did this with Cub Scouts, I kept calling the canister a rocket, and they called it a canister, until the first time it flew. When Cubs was over that day, one rocket had been left behind. About an hour later a Cub came looking for his "Rocket". It's been a success ever since.   It is also a great demonstration on how gases can build up in a container and keep building up until released (that’s how we get the pop). I will share the basic rules that I have put in place for safety and organizational purposes.  So, this is the Alka Seltzer Rocket Activity.

Step 1:

Supplies:
Clear empty 35 mm film canisters with the lid that fits on the inside of the canister.  (These are getting hard to find.  Used to be you could go to places that developed film and they would just give them to you.  Two websites that carry these are: http://www.sciencebobstore.com/products/Bulk-Film-Canisters-for-Rockets.htmland and http://www.filmcanistersforsale.com/  or just Google it.
Alka Seltzer tablets (save a small fortune and buy the genetic brands +/-$4 for 36 tablets) Water
Stickers and or
Color permanent markers
Water