Monthly Archives - February 2008

Alka Seltzer Rockets

This summer CoolStuff News caught up with science presenter Marcey Walsh. (See HighlyContagious.com) We asked her, “What would be a great activity to get kids thinking like scientists again after the long summer break?” Here’s what she suggested…

“You can’t beat a simple, inexpensive science whiz bang! Kids love the excitement and surprise of an exploding “rocket.” I use it at every opportunity as an example of cause and effect. For instance: When you have kids ( canister)… and curiosity (Alka Seltzer®)… and add all the stuff you learn from reading books (H2O) Something amazing happens…
(pause dramatically while waiting for explosion) Incredible ideas happen!

ALKA SELTZER ROCKET ACTIVITY INSTRUCTIONS

THIS EXPERIMENT REQUIRES ADULT SUPERVISION

What you’ll need:

  • Safety goggles
  • One Alka Seltzer® tablet (brand or generic)
  • One white film canister with a snap on cap*
  • Small amount of water (one tablespoon or less)
  • Paper towel for clean ups

*WHITE film canisters from your local pharmacy or film developer can be had for the asking (white ones have a tighter seal than the grey or black ones). Collect a bag of these, they are becoming rare!

What to do:

  1. Put on Safety goggles
  2. Break an Alka Seltzer® tablet into quarters
  3. Put two quarters of the tablet into the film canister
  4. Add less than a tablespoon of water
  5. Snap the lid tightly onto the canister
  6. Turn it over and STAND BACK!!!
  7. Count down from 5 to predict when the explosion will occur.*

*If you see bubbles around the base, your canister does not have a tight seal. It may still explode eventually.

How come?

The chemical reaction between the molecules in the Alka Seltzer® tablet and the water (H2O) molecules produces the gas carbon dioxide (CO2). A property of a gas is to expand to fill (or overfill!) it’s container. The pressure pops the top – or bottom- off!

Extensions:

  • I tape sparkly streamers to the bottom of the canister. This makes the flying “rocket” more visible from a distance. It’s also fun to decorate it like a rocket or an animal or person, then let them fly! (What happens when you add too much weight to the canister?)
  • Repeat the experiment but leave canister top up and bottom down, how is the result different? Why?
  • Is there any change if you don’t break up the tablet?
  • Does it make any difference if you add more Alka Seltzer® or more water?
  • Repeat this experiment using a quart size Ziploc® bag in place of the film canister. What happens when the container is flexible? Why?
  • Repeat the experiment with a grey canister. Was your result different? Why?

WARNING: Sometimes the reaction takes longer than expected. If “rocket” does not explode, place one hand over the canister and use the other hand to pop the top off and release the pressure. Do NOT lean over the canister or severe eye damage could be caused by an unexpected explosion!

Marcey Walsh boosts the science confidence of thousand of teachers nationally each year! Her fun, interactive staff workshop “Rock Solid Science” explores the five concepts in Physics that are the foundation for every science unit you teach! Check out Highly Contagious Education at http://www.highlycontagious.com

Engage, Explain, Explore, Expand and Evaluate…

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