1. Tear up two or three red cabbage leaves
into small pieces. Place the pieces into a zip-closing
plastic bag. Add one cup of warm water to the
bag and seal it tightly.
2. Squeeze the leaves in the bag until the water
turns a dark blue color. This is your indicator
solution. An indicator can change color when certain
substances are added to it. Use masking tape and
a pencil to label two of your cups A and B. Pour
1/4 cup of the indicator into each of the two
cups.
3. In a separate cup, add 1/4 cup of water. Place
one Alka-Seltzer tablet in the water. Wait for
the tablet to dissolve completely. Use your straw
to place five drops of Alka-Seltzer solution into
cup A. Swirl the cup. What do you see? How does
the color in cup A compare with the color is cup
B?
4. Look at the ingredients on the package of
Alka-Seltzer. Aside from aspirin, the ingredients
are sodium bicarbonate and citric acid. Sodium
bicarbonate is baking soda, and citric acid is
the acid in citrus fruits such as lemons and oranges.
CHALLENGE! See if you can add the right amounts
of lemon juice and baking soda to the indicator
in cup B to produce the exact color that the five
drops of Alka-Seltzer solution produced in cup
A. Here's how to do it!
Add one drop of lemon juice to the indicator
solution in cup B. Swirl the cup. If this does
not match the color of the solution in cup A,
use your toothpick to add a small amount of baking
soda to cup B and swirl again. Keep track of the
exact amounts of lemon juice by drops and baking
soda by toothpicks you are adding. Observe the
colors in the two cups very closely.
5. When you think you know the right amounts
of lemon juice and baking soda, rinse out cups
A and B to get ready to test your results. Place
1/4 cup of indicator in cups A and B. Add five
drops of Alka-Seltzer solution to cup A as before,
and swirl. All at once, add the exact amount of
lemon juice and baking soda that you think will
match the color in cup A, and swirl. How did you
do?
Back to top |
