Mathematics/Physics

Introductory Lesson on How pH Levels are Determined

Objective(s):

1) To introduce the student to pH levels using household materials.

2) To make students aware of the importance of pH levels in their day to day lives.

Materials Needed:

Provide as many household items as possible: lemon juice, lime juice, white vinegar, tomato juice, seltzer water, tonic water, boric acid, distilled water, pineapple juice, shampoo, facial cleansers, bleach, hair relaxing solution (testing for the absence of lye), borax, washing detergent, alcohol, peroxide, soda pop, baking soda, Maalox, Liquid Plumber - (any other products you can think of). For station three you will need wet soil, pH tester, litmus paper (blue and pink), small Dixie cups, rubber gloves, plastic spoons, Hydrated Lime, Aluminum Sulfate, pH chart, coffee cups to test soil in, small starter planters, rubber gloves, droppers, test tubes, teacher-generated worksheets, goggles (optional).

Strategy:

Because this is an observation lesson the classroom should be made as festive as possible to make the presentation inviting and exciting. Prior to this lesson students will have been introduced to the concepts of acids and bases. Students must have an understanding of a pH scale. The class should be divided into 3 to 4 groups in which each will test a different item and record their pH findings, determining if the material is neutral, basic, or acidic.

Station #1:

At station #1 each student will be given one pink and one blue litmus strip and asked the question: "What do you see happening?" (This will prepare the minds of the pupils to form hypotheses at station #2.) At station #1 have 10 products (or enough products that will accommodate the number of students in each group). Each participant in each group will be able to test a different product and compare it to the pH chart and determine if it is acidic, basic, or neutral. The teacher should continually ask the question: "What do you see happening?" reinforcing their observation skills. Students will chart their findings on a form provided by their teacher. A pH chart should be at each table.

Station #2:

At station number #2, the question will be posed, "What do you think will happen?" At this station there will be a number of products. Each student will be given litmus paper to test the pH levels of each item. Students should be able to form this hypothesis based on what they have learned and experienced at station #1. Students will chart their findings on a form provided by their teacher.

Station #3:

At this station the question will be posed, "What do you know will happen?" Teacher will guide students through the steps to successfully perform an experiment, using the scientific method. At this station, students will take a cup of wet soil, first testing the soil with the pH meter to determine if the soil is acid or alkaline. Students will then determine how they could make the soil become acid or alkaline (basic), by adding hydrated lime or aluminum sulfate to the soil to get the desired results.

Performance Assessment:

The final culminating assessment activity will be for the students to find a plant and determine what the best soil conditions would be for this plant. Students will be paired into groups of two. One student will create the perfect soil conditions for the plant which they choose. The other student will take the same plant but will not add anything to the soil. Each student will be responsible for charting the development of their plant for 4 weeks. Then, each group will be responsible for outlining and reporting their findings. The whole class will be assessed using this method.

References:

Science Junction

Beakmans’ World

http://www.beakman.com/acid/acid.html