Monday, May 18, 2009 8:50 AM

The pH Scale --September 9, 2009

TEK 3(F) The student will collect data individually or collaboratively, make measurements with precision and accuracy, record values using appropriate units, and calculate statistically relevant quantities to describe data, including mean, median, and range.

TEK 3(G) The student will demonstrate the use of course apparatuses, equipment, techniques, and procedures.

Time Span: Three 45 Minute Periods to complete this assignment

Introduction:  In this lab, students will be given an opportunity to use a Digital pH Meter and Hydronium pH paper to collect pH readings on the substances listed below.  They will record the values with precision and accuracy using the appropriate unit of pH.  Once the student records the pH on a table and the pH Scale, then the student will describe what each value means in terms of Hydrogen Plus One Ions,  Hydronium Plus One Ions, and Hydroxide Negative One Ions.

Materials Needed:  The materials listed here are for a class lab group of 24 students. 

(6) pH Digital Meters, (6) Rolls of Hydronium Paper, (6) 25 mililiters of Tide or Gain, (6) 25 mililiters of Black Coffee, (6) 25 mililiters of distilled water, (6) 25 mililiters of Lemon Juice, (6) 25 mililiters of Ammonia, (6) 25 mililiters of Vinegar, (6) 25 mililiters of Coca Cola, (6) 25 mililiters of Dr. Pepper, (6) 25 mililiters of Pepsi, and (6) 25 mililiters of Drano.

Assignment: Using a Digital pH Meter and Hydronium Paper, take pH readings of the following substances:

A. Detergent

B. Black Coffee

C. Pure Water

D. Lemon Juice

E. Ammonia

F. Vinegar

G. Coca Cola

H. Dr. Pepper

I. Pepsi

J. Drano

The following substances and their pH readings are on the pH Scale that is listed underneath.

Define the following terms:

1. pH Scale

2. Acid

3. Base

4. Anion

5. Cation

6. Ion

7. Hydrogen Ion

8. Hydronium Ion

9. Hydroxide Ion

10. Neutral

Using the above terms have students take pH readings and use the above vocabulary to engage them in analytical reasoning.

Record all pH and Hydronium readings on a Table and on a pH Scale like the one listed below. 

Describe how there are differences in precision and accuracy between the Digital Readings and the Hydronium Paper Readings. 

Students should complete the following essay question:

Describe how the following substances that have been tested impact the environment and especially the health of an individual over a long period of time.  The time span is 10 years or longer.