THE LOST EFFERVESCENCE  LESSON

 

The Mystery of Christa’s Big Bubble

 

 

“See the bubbles…the big one…I love it.”

Background Science Summary:

 

Effervescence, i.e., the presence of bubbles in a liquid, can be produced  both by a chemical reaction and physical phenomena.  The chemical compound contained in an Alka-Selzer® tablet produces effervescence through a chemical reaction.  The tablet with its chemical formula, NaHCO_3,  is also known as “baking soda” or sodium bicarbonate. When dissolved in water, the chemical reaction occurs.  It  results in the tablet  producing, as a byproduct,  a gas known as carbon dioxide with the symbol, CO₂ .

Of course, effervescence can be produced in water by simply blowing  carbon dioxide gas into the liquid, pressurizing it.  No chemical reaction is involved.  However, the pressure of the gas within can be affected through physical means (shaking).

 

Hypothesis:

 

The size of carbon dioxide bubbles formed by the effervescent chemical reaction is affected by the scale (size) of the Alka-Selzer® granules as well as the physical shaking of the contents.  

 

Materials:

1. Alka-Selzer®  tablets in bottle
2. Plastic safety goggles
3. Roll of paper towels for cleanup
4. Empty peanut butter jar and screw on lid
5. Half gallon of tap water in plastic container
6. Watch with second hand
7. Tablespoon and teaspoon for crushing tablet
8. Ruler
9. (Optional) Video Camcorder with flip out playback screen

 

Procedure:

(Optional: Have an assistant video tape the procedure just as Christa was video tapped.)

 

Deposit an Alka-Selzer® tablet in the water bottle.  After the tablet dissolves in the clear jar, observe the size and number of  bubbles within the  water.  Shake the jar vigorously.  Do the number of bubbles increase?  Does the size of the bubbles increase.  What do you think causes the increase in pressure as a result of the shaking?  How does the shaking contribute to bubble size and quantity? What is going on with the bubbles in the closed jar?

 

What Happened?

 (Study the video tape by clicking below.)

 

The chemical reaction began when the sodium bicarbonate tablet mixed with water. The chemical reaction released carbon dioxide. The gas was contained in  the bubbles seen in the water. Alka-Selzer® tablets are known as an antacid or “base”. An antacid is the opposite of what is called an “acid”.  A base’s purpose  is  to weaken (neutralize) acid levels in the stomach. Obviously, acid in contact with the stomach’s lining causes discomfort.  As such, the tablet provides relief from indigestion and “heartburn.”

 

While it is true that the carbon dioxide gas was produced by the chemical reaction, what about a non-chemical or physical change causing the pressure and size of the carbon dioxide bubbles to increase?  For example, have you ever shaken a bottle or can of a carbonated beverage then opened it.  The shaking increases the pressure of the gas within the vessel.  When opened, the liquid beverage spews out with the over-pressurized carbon dioxide gas.  Obviously, only the shaking can be blamed for the increase in gas pressure.  Was the chemical reaction responsible for the  bubble’s size?

 

(Carefully view the following video for the explanation voiced by Bob Mayfield.) And, additionally, what effect did having no gravity contribute to the bubble’s size? 

 

Discussion: Why did one of the bubbles produced by the CO2 gas become so much larger than the others?  A major clue is revealed by the video of the capsule dissolving in the water.  See if you are able to replicate the formation of the large bubble based on the explanation voiced in the video. 

 

Finally:  Christa performed the effervescence demonstration both without gravity, on the KC-135 zero G aircraft, and in the shuttle mock-up area of the Johnson Space Center .  Carefully view both videos.   What, if anything, is alike and what is different about the two times the experiment was conducted?   Click on the video panels below for your assessment.

 

Based on your findings, if you had an upset stomach, would you rather ingest an Alka-Selzer® tablet in space or on the ground.  Discuss the reasons for your answer based on comparing how the tablet dissolved in zero-G and one-G. 

 

Effervescence in Zero G

Click on

effervescence_zero_G.wmv (2.0 MB, hi-res wmv file 4.0 MB )

to play the video clip.

 

 

Efferescence in One G

Click on

effervescence_in_one_G.wmv (1.8 MB, hi-res wmv file 4.7)

to play the video.

 

 

Back to the Table of Contents

 

For added information or copies of the project, contact the project editor Jerry Woodfill, at ER7, NASA JSC, Houston , TX 77058 .  Phone: 281-483-6331,  E-mail: jared.woodfill-1@nasa.gov

 

The project is a work of the Automation, Robotics, and Simulation Division of the NASA Johnson Space Center , Houston , Texas . As part of the Space Educators’ Handbook, its ID identifier  is OMB/NASA Report #S677.