Teacher Instructions
Help the Rainbow fish find his colors!
Grades K-4
Ana Shapiro
January 11, 2010
The objective of this lab is to define physical and chemical changes, acids
and bases and to observe the different chemicals involved in black inks,
washable markers and colored candies. Any of a chemicals properties that are
observed during a chemical change
Chemical Property Any of a chemical’s properties that are observed during a
chemical change. Examples: flammability, acidity, how basic a chemical is
Intrinsic property an inherent property like color or density, a property that does
not depend upon how much of an object is present
Extrinsic property a nonessential or inherent property of an object that may
depend on how much of an object is present such as mass or height
Acid any compound that gives on hydrogen ions when dissolved in a
solution, it must have a pH lower than 7
Base a substance that can accept hydrogen ions, it must have a pH higher
than 7
pH a substance’s ability to give off or accept hydrogen ions, the scale is 114
neutral- having a pH of 7
Materials:
Cabbage juice ice cubes (can be made in Dixie cups)
Clear glasses
Vinegar
Baking soda
Water
Cabbage juice
Straws
Coffee filters
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Black pen
Black permanent marker
Black washable marker
Colored washable markers
Skittles
Procedure
Give each group a glass of vinegar, a glass of water and a glass of water mixed
with about a tablespoon of baking soda. Also give each group three cabbage
juice ice cubes, have them drop one in each glass and see what happens.
Discuss what happens. Before putting the frozen cabbage juice in the
solutions discuss which solution is acidic, which is neutral and which is basic.
Then discuss what the cabbage juice test tells us. Now pass around a glass of
cabbage juice and give each student a straw. Tell them to blow bubbles into the
cup for a moment and then pass it on. After it has been passed around hold the
cup up to another cup of cabbage juice that has not had bubbles blown into it.
The first cup is purple now instead of blue. This means that blowing bubbles into
the glass has made it slightly acidic because the CO2 from our breath is
dissolved in the solution (mention that many gasses can be dissolved in liquids).
The reaction of CO2 and H2O produces carbonic acid.
Prior to the chromatography section of the lab, cut the coffee filters into strips.
Give each group three initially and have them draw a black dot on each using the
washable marker on one, the black pen on one and the permanent marker on
one. Then place the strips into a beaker with a small amount of water at the
bottom of it. Have the class draw what happens.
Repeat the procedure with colored markers and then with skittles. (Pigment can
be taken from the skittles by rinsing them with water and then using a finger to
dab a bit onto the strip. Have the students draw what happens.
Discuss what is happening and how different black inks may involve
different chemicals, some that are colors other than black.
Time Requirements
This lab should take about an hour. If running out of time, you can cut down on
the chromatographies or assign different chromatography tests to different
groups.
References
The Usborne Big Book of Experiments by Alastair Smith
Championship Science Fair Projects by Sudipta Bardhan-Quallen
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Name:_____________________
Help the Rainbow fish find his colors!
Part One: Use deep ocean blue and clear liquids to make pink and blue green.
You have three clear solutions, vinegar, water and baking soda and water. Draw
lines to show which is an acid, which is a base and which is neutral.
Vinegar
Base
Baking soda solution
Neutral
Water
Acid
Draw what happens in each solution after you add the dark blue ice cube (this is
frozen cabbage juice).
Water
Vinegar
Baking Soda Solution
What happens when cabbage juice interacts with an acid?
What happens when cabbage juice interacts with a base?
What happens when cabbage juice interacts with a neutral solution?
What does cabbage juice tell us about a solution?
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Part 2: Find the colors in black!
Place a black dot about one inch above the end of each strip of coffee filter paper
using the black pen, the black washable marker and the black permanent
marker. Pour a very small amount of water into the beaker then carefully place
each strip in, with the dot side facing the water (but try to make sure the dots
don’t actually touch the water).
What does the water do as it touches the filter paper?
After the water passes the black dot what happens? Does the same thing
happen for each black dot?
After 5 minutes draw what each strip looks like
Part 3: What colors can we find in other colors?
Use the washable colored markers to dot filter paper and place the strips in the
water to see what happens.
Also you can see what colors we can find from the coloring on skittles by running
water over the skittle, and then using your finger to dab a bit of color onto a filter
strip.
Do any of the colors surprise you?
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Draw the strips and be sure to label which color the initial dot was for each strip.
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