MnSTEP Teaching Activity Collection > MnSTEP Activities > Analyzing pH: Comparing Citrus Fruits, Stain Removers and a Green Product

Analyzing pH: Comparing Citrus Fruits, Stain Removers and a Green Product

Carol Hultman, Central Middle School, White Bear Lake, Minnesota 55110
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Summary

The students will analyze the pH of four citrus fruits: lime, lemon, orange, and a grapefruit, and then they will analyze the pH of four different types of stain removers:
Shout Advanced, Spray 'n Wash Max, Oxi Clean Laundry, and Clorox Oxi Magic. Using their learned information, they will predict and then analyze the pH of a final cleaning solution Bathroom Lime & Scale Remover, which is a Green product.

Students will use two methods of determining the pH for comparison. This will be done utilizing pH litmus paper and creating a cabbage indicator solution.

Students will also read labels, list the first few ingredients, and identify sales tactics used for their products such as eye-catching phrases. (Language Arts)

Finally, students will discuss and share their results as a class. Students need to answer what do citrus fruits have to do with cleaning? What product is most effective? Students need to support their answer with data from their experiment.

Learning Goals

  • Students will develop skills in measuring tools.
  • Students will develop lab techniques in analyzing the pH of substances.
  • Students will analyze lab results and other resources before presenting their conclusion. Students will learn that the Green cleaning product consists of natural citrus products.
Concepts:
  • The student will understand the scientific method is a systematic way to test their investigative questions.
  • The students will understand pH of solutions is measured on a scale of acid to base in varying intensities.
Vocabulary:
  • pH
  • acid
  • base
  • Green products
  • surfactants

Context for Use

This lab is intended for sixth grade students or higher. It can be used with a large class divided into small lab groups of 2 to 4 students. It would be best done in a classroom with available water. This lesson could easily be divided into two to three days of activities. This activity can be done at tables. Students should have some knowledge of the periodic table and that elements combine to make matter.

Subject: Chemistry:General Chemistry:Acids & Bases,
Resource Type: ActivitiesLab Activity, Classroom Activity
Grade Level: Middle (6-8)

Description and Teaching Materials

Activity #1 - Setting the Stage

LEAD THE CLASS IN A DISCUSSION ABOUT: Students should carefully look at the solutions and observe - color, thickness of solution, odor, can it make bubbles by blowing a pipette in the container? Use this process to lead to further investigations:

O K W H L

(Language Arts) Develop an understanding of consumer awareness to marketing techniques. Make a matching activity for catch phrases used on these products to attract consumers. Take a class survey: number in order of which product best matches your needs.

Shout - Set In Stains - Advanced
Spray 'n Wash - MAX Resolve Power
Oxi-Clean - Fast Acting
Clorox Oxi-Clean - Multi Purpose Stain Remover

Develop a habit of reading labels. Make a matching activity to focus on the labels:

Look for ingredients and match: (I used only the first two or three ingredients)

Shout - Surfactants
Spray 'n Wash - Hydrogen peroxide and Surfactants
Oxi-Clean - Surfactants and Hydrogen peroxide
Clorox Oxi-Clean - Hydrogen peroxide, Isopropyl alcohol, and Surfactants

Activity #2 - pH Testing

Explain the lab technique of pH testing. Tell the students that they will be using a chemically treated paper (litmus paper) and a naturally made indicator (Red cabbage) to test the pH of these products and natural citrus fruits.

Find the pH of each solution and juice of each citrus fruit using litmus paper and then the cabbage indicator. Rank in order of color from a red to yellow and then blue to violet/purple. Take a picture of these results to use as a chart later for comparison to the mystery product.


Activity #3- Analyzing the Mystery Product

Now give the students the mystery product. Read the label and the ingredients and predict what pH factor this product will have. This is the Green product: Bathroom Lime & Scale Remover. It is biodegradable and its main ingredient is citric acid.

Compare and contrast the pros and cons of all products. Ironically, the Green product cleaner is made from biodegradable elements (citric acid) and is earth friendly.

Teaching Notes and Tips

I tried this lab myself and was amazed at the pH indicator outcome. It also allows for other property identification as suggested in this lesson. I would caution the students of the chemicals used in the chemical products and use lab goggles. This will also help them realize how much safer it is in using the Green product. I begin reading labels when I introduce the periodic table with rice krispy bars. The web site for them is great. You can download the DVD, music and lyrics. Also learn Snap, Crackle, and Pop in seven languages. The bars are made from three ingredients in the home recipe. We focus on the marshmallow made from sugar. Then we discuss the chemical formula for sugar: C, H, and O. This lesson builds on how to read those ingredients on product labels.

Assessment

  • Students will create a pH photo from their lab testing. Take a photo.
  • Students will match product with catchy consumer phrases and first few ingredients.
  • Students will apply knowledge to a mystery product and analyze and write a comparison/summary of their findings. Collect outcomes.

Standards

MN Academic Standard:
6.A.1.2. - Scientific World View
6.I.B.1.2.3.4. - Scientific Inquiry

References and Resources