Enzymes as Catalysts

Lesson Plan

State Standards:



Essential Question:

What is the relationship between the pH of a substance and whether it is biological or non-biological?

Lesson Question:

How do acidity/alkalinity relate to the origin of a substance?


In this lesson, you will review the mathematical relationship between pH and H+ content. You will prepare solutions of biological and non-biological substances. (If needed, use a morrtar and pestle to crush the biological samples.) You will use computer-based probes to find the pH of each prepared solution. Finally, you will compare the pH of each substance to its origin (biological or non-biological.)


You will see how pH relates to H+ ion content. You will prepare solutions of biological and non-biological substance and use a computer-based system to find the pH of each solution. Then, you will compare the pH values between the substances and look for patterns.



A common misconception with pH is that students believe that high pH is related to high H+ concentration, when just the opposite is true. This will be addressed by having students compare H+ levels to OH- levels.

Lesson Experiences:

After the students have completed the lab, students may find the image below helpful.

Ph and H+.  Image from


This lesson serves as an introduction to pH. It will connect student's previous exposure to pH in physical science classes to the materials they investigated in the previous year's biology class.


Lesson Rubric:

Lesson Rubric

Printable version of rubric.


  1. Vernier (or similar) pH probes + software
  2. test tubes
  3. pipets
  4. scooper
  5. mortar/pestle
  6. water
  7. biological substances:
    • lettuce
    • onion
    • tomato
    • ground beef
    • yeast solution
  8. non-biological substances:
    • vinegar
    • soap/surfactant
    • sodium chloride
    • ammonia
    • bleach
    • ammonium nitrate
    • calcium chloride

Online resources:

  1. Introduction to Vernier LabPro
  2. Introductory quiz