When dry ice is added to a graduated cylinder containing blue liquid (basic water with universal indicator), the dry ice produces bubbles and fog and turns the solution yellow.

 

TO CONDUCT DEMONSTRATION:

1.       Drop dry ice chunks into a graduated cylinder filled with a basic solution and universal indicator.

2.       Ask students to make as many observations as possible.

EQUATIONS:

CO2 produces H+ in solution and neutralizes OH-.

CO2(aq) + H2O(l) —> H2CO3(aq) + 2H+(aq) + CO32-(aq)

H+(aq) + OH-(aq) —> H2O(l)

 

SAFETY AND DISPOSAL:

Eye protection should be worn to avoid splashing base into the eyes.

 

PRIOR TO LECTURE:

1.         Dissolve 6.5g KOH (potassium hydroxide) in 1600mL water and add several drops of universal indicator.  Place in 2000mL graduated cylinder.

2.         Assemble the following:

            a.         dry ice in 2" chunks

            b.         tongs or heat-protective gloves

            c.         goggles

 

REFERENCE:

L.R. Summerlin and J.L. Ealy Jr., Chemical Demonstrations:  A Sourcebook for Teachers, 1985.

ACKNOWLEDGMENT:

Patrick McKeown, Summer 1989.