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Lab 10 – Measuring pH

Standards

Oklahoma Standard: HS-PS1-2: Matter and its interactions (chemical reaction explanations).

Construct and revise an explanation for the outcome of a simple chemical reaction based on the
outermost electron states of atoms, trends in the periodic table, knowledge of the patterns of
chemical properties, and formation of compounds.

  • Lab Emphasis: Devise experiments – use trial/error for colors
  • Science & Engineering PracticePlan and conduct investigations
  • Cross-Cutting Concept: Cause and Effect: Cause and Effect: Mechanisms and explanations

Five part activity summary

This lab includes: preparation, pH art, neutralization activity, student designed predictive experiment, and supplementary balancing of equations. The lab demonstrate basic concepts associated with the measurement of pH. The use of cabbage juice as a universal indicator is instrumental to completion of the activities. Print and distribute instructions and lesson plan, student handout, and print/post applicable SDS sheets along with safety review with students.

pH art overview

Below, find videos describing the use of a “Universal Indicator” for pH (the natural dye from red cabbage) to identify relative acidity in solutions. Dye, then dry, white coffee filters with cabbage juice. Use Q-tips® – or similar cotton swabs – to apply various household acids and bases to the dyed coffee filters. (CAUTION: some household products are equally as dangerous as chemicals in a lab. Use appropriate care and caution with all chemicals). Allow students to “paint” their coffee filters and make art.

Lab Instructions (Lesson Plan)
Topic Introduction Material (Day 1)
The Lab Activity (Day 2)

For the Lab, provide each student with a cabbage juice dyed coffee filter, Q-tips, lemon juice, baking soda, hydrogen peroxide, dish soap, and other similar household products. Allow students to “paint” their coffee filter by using household acids and bases. Use and enforce appropriate lab behaviors.


3:02 Teach science with art.

3:10 What is the pH scale | Chemistry for All | FuseSchool

4:34 Make your OWN pH Indicator from Red Cabbage!

2:16 Watercolor Painting Tips – Dabbing with the Brush

1:51 DIY watercolor painting with cotton swabs


Compare Contrast and Debate

Kick-Off Debate Background: Chemistry instructors often have a choice to either use (A) commercial-grade chemistry supplies, or (B) household products. While both approaches can demonstrate chemistry concepts – there are pros and cons with using each approach.

  • Position A: Commercial-grade supplies should be used. They are consistent, proven, and more professional.
  • Position B: Household-type of supplies and products should be used. They are less expensive and more meaningful to students.

Special Notes and Notices

Applicable SDS Sheets

Instructor Emphasis:

  • Lab Emphasis: Devise experiments – use trial/error for colors
  • Science & Engineering PracticePlan and conduct investigations
  • Cross-Cutting Concept: Cause and Effect: Cause and Effect: Mechanisms and explanations
  • Lab procedures
  • Use of equipment
  • Data gathering
  • Data measurement
  • Interpret results