*Students will read about and be given instruction on the pH scale, how it relates to the concentration of hydrogen ions in solution, and how to use a formula to calculate pH and H+ concentration.

*Students, working in cooperative groups, will complete a set of practice problems on finding pH and H+ concentration. Allow one set of problems for each group. Click here for a practice worksheet.

Practice Problem Answers(Click on link)

Materials needed: classroom, text/background information, worksheet of practice problems, calculator.

Activity Two

Students will use EXCEL software to create a spreadsheet of pH data, calculate H+ concentration, and graph pH versus H+ concentration.
Time allotment: 1-2 class period/s

*Students will need a list of common substances and their pH values. This list can be obtained through a simple experiment (see Physical Science section, lab activity) or a list can be obtained by using this interactive tool. Teachers may also prepare a list and give it to students directly.

*Students will enter the pH data into a spreadsheet. The table should have three headings: Substance, pH, and H+ concentration.

*Students will need to enter an appropriate equation into the last column to obtain the H+ concentration from the pH values. Students should figure out the equation by themselves.
[This equation will be =10^(- cell no. of pH)] Do not enter the words “cell no. of pH” but enter the actual cell number of the pH value in the spreadsheet. (Click to see example)

*Students will create a graph (scatter plot) of the pH versus the H+ concentration. Hint: When the students first create the graph it may appear with loops or overlapping sections. This will happen if the students do not SORT their data. Students should get a nice exponential curve with no overlaps after they SORT the data in ascending order. See example(large graph).

*The graph will show a very large range of H+ values resulting in many points appearing to have a pH of 0 at the end of the curve. To help students see these values more clearly they will create a second graph (scatter plot) using the last four data values in the table only. (These will be the four values with the highest pH.) This smaller graph will show that these last points are not all the same. See example(small graph).

*Students will interpret the graph/s to determine the relationship between pH and H+ ion concentration and how this relationship is expressed in the pH equation.

Materials Needed:
Student Guide sheets, sample data of common substances and their pH values, computer, EXCEL spreadsheet program, Internet access (optional).

Click for a printable copy of the Student Guide for Activity Two.

Click here for a printable copy of the Answers to Activity Two.

Developed by

This project is supported, in part,
by the

National Science Foundation

Opinions expressed are those of the authors
and not necessarily those of the National Science Foundation.