Education Technology

Sour Chemistry: The Exponential pH Change

Published on 07/02/2009

Activity Overview

In this activity, students' will use a pH sensor to record pH versus time data as an antacid tablet neutralizes acid in lemon juice. They will model the pH data with a modified exponential function.

Before the Activity

  • Connect the pH probe to Channel 1 on the CBL 2™ or Vernier LabPro®
  • Connect the CBL 2 or LabPro to the calculator using the Unit-to-Unit cable
  • See the attached PDF file for detailed instructions for this activity
  • Print pages 199 - 205 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to your class.

    Follow the Activity procedures:

  • Place about 125 ml of distilled water in a very clean cup
  • Place the pH sensor in the water
  • Add drops of lemon juice to the water and stir gently
  • Drop the effervescent tablet into the water and measure pH every 0/5 seconds for 50 seconds
  • Plot the pH versus time graph
  • Use a modified exponential equation to model the data
  • After the Activity

    Students will analyze data and complete the Data Collection and Analysis Sheet. They will also answer questions listed in it.

    Review student results

  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary