Introduction
This A Fun Magic Coloring Book is an excellent way to teach observation skills to your students. The coloring book pages appear to contain different pH indicators that “magically” turn colors when exposed to an acid and are erased, or become colorless, when neutralized by a base.
Concepts
- Observation
- Acids and bases
- pH
Background
A Fun Magic Coloring Book has three pages in each set. The first page is an uncolored picture, the second page is the same picture that has been colored, and the third page is blank. The uncolored pages are cut so they stick out farther than the other pages at the top of the book. The colored pages stick out farther in the middle of the book, and the blank pages stick out farther at the bottom of the book. Closely examining the pages makes this readily apparent. The position of your hand at the top, middle or bottom determines the page of each set that the students will see as you flip through the book.
Materials
Tap water A Fun Magic Coloring Book* Beakers, any size, 3 *Materials included in kit.
Safety Precautions
Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines.
Disposal
Save all materials for future use.
Procedure
- Label one beaker “NaOH” (sodium hydroxide).
- Label a second beaker “HCl” (hydrochloric acid).
- Label a third beaker “Bleach” (sodium hypochlorite).
- Pour enough water into each beaker so each beaker is approximately half full.
- Hold the bound edge of the book with your right hand. The book should be in front of you so that the pages, when opened, will face the students.
- Place the fingers or thumb of your left hand against the upper portion of the book (the top 3.5 centimeters) and flip the pages slowly from the front of the book to the back. This will allow the students to see the set of uncolored pictures in the book.
- Hold the book by the spine and fan the pages over the beaker labeled “hydrochloric acid” a few times.
- Hold the book up to face the students again and place the fingers or thumb of your left hand against the middle portion of the book. Flip the pages slowly from the front of the book to the back. This will allow the students to see the set of colored pages in the book—it will appear to students that the uncolored pages (pH indicators) in the book have become colored after being exposed to the “acid fumes.”
- Hold the book by the spine and fan the pages over the beaker labeled “sodium hydroxide” a few times.
- Hold the book up to face the students again and place the fingers or thumb of your left hand against the top portion of the book. Flip the pages slowly from the front of the book to the back. Now, the students will see the original uncolored pictures in the book since the pH indicators have been erased after being “neutralized” by the “base fumes.”
- Repeat steps 5–10 several times.
- Discuss this event with the students and get them to question why the colors appeared and then disappeared. Discuss how acids and bases neutralize each other and how pH indicators “indicate” if an acid or base is present.
- Finish the trick by exposing the coloring book to the “bleach fumes.” Hold the book by the spine and fan the pages over the beaker labeled “bleach" a few times. Explain that, since bleach removes colors and stains from clothing, the bleach should remove all images from the pages, including the black outlines.
- Hold the book up to face the students again and place the fingers or thumb of your left hand against the bottom portion of the book. Flip the pages slowly from the front of the book to the back. Now students will see that the pages in the book have been completely erased by the “bleach fumes.”
- Lead them to understand that the magic behind the event is not due to any chemical change but was due to the way each page in the set is cut.
Teacher Tips
The students may believe that the pages actually contain pH indicators. A good way to show them that they do not is to wave a piece of pH paper over the beakers and show them that no color change takes place. To avoid the misconception that each color is indicating a specific pH, similar to universal indicator, tell the students that the pages are already colored with different indicators and that each exhibits a different color at the same pH. Refer to the indicator chart in the chemical section of the current Flinn Scientific Catalog/Reference Manual that shows indicator colors at different pH ranges.
- Practice before performing in front of students.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering Practices
Analyzing and interpreting data Obtaining, evaluation, and communicating information
Disciplinary Core Ideas
MS-PS1.A: Structure and Properties of Matter HS-PS1.A: Structure and Properties of Matter
Crosscutting Concepts
Patterns Cause and effect Structure and function
Performance Expectations
MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. HS-ESS2-3: Develop a model based on evidence of Earth’s interior to describe the cycling of matter by thermal convection. HS-ESS2-5: Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.
References
Flinn Scientific would like to thank Lee Marek, University of Illinois–Chicago, and John J. Fortman, Wright State University, for sharing this idea with Flinn Scientific.
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