Lesson Plan Justification Acid-Base Titration Experiment Michael Scott Martin Wednesday, 10 March 2004

Acids and bases are among the most common chemicals that students will encounter in

daily life. Though they may not realize it, students will encounter acid-base reactions every day.

The purpose of this lesson is to help student to become more familiar with acids and bases and

the way they react.

Students will use a spreadsheet program and a digital pH meter to track the progress of an

acid-base titration. Both of these tools make it easier for students to see how an acid-base

reaction proceeds.

One way to demonstrate the progress of an acid-base reaction is to show the acidity, or

pH, of the reaction solution at various points in the reaction. Many people are probably familiar

with litmus paper. It is a chemical indicator that shows the pH of a solution by changing color.

Other chemical indicators, like phenolphthalein, show by a color change when a solution reaches

a specific pH. Chemical indicators are of limited usefulness in tracking the progress of a

reaction over a wide pH range, however. Phenolphthalein, for example, only shows whether a

solution is above or below a specific pH. On the other hand, universal litmus paper shows

various pH values, not only to within 2-3 pH.

A better tool for tracking the pH during the course of an entire reaction is a digital pH

meter. This tool shows the pH of a solution to two decimal places or more. Furthermore, it is

effective over the full range of pH values from 0 to 14. Using the digital pH meter, it is therefore

possible to detect very small changes in pH at all stages of the reaction. This helps the students

to see that the change in pH is small at some points in the reaction and large at other points. This

gives the students a better idea how an acid-base reaction proceeds in different stages.

Once students have collected pH data for a reaction, they can easily use a spreadsheet

program like Excel to display their information graphically. While such a graph can be

constructed manually with a pencil and graph paper, the resulting graph can often be messy and

the plotted points can be inaccurate. The spreadsheet allows the student to produce a more

accurate, higher quality graph that they can then use to estimate the progress of future reactions.

By producing a visual record of the progress of the reaction, the spreadsheet can help students

predict how acids and bases will behave in other reactions.

The intent of using technology in this lesson is to help students more easily see and

process numerical data related to a chemical reaction. The digital pH meter gives students a look

into the small-scale changes of a chemical reaction that are not visible to the eye. The

spreadsheet allows students to display and interpret the results of their experiment more clearly.

Both tools are geared toward improving productivity.