Introduction to pH | Biology | Khan Academy

Introduction

This tutorial will introduce you to the concept of pH, its significance in biology and chemistry, and how it is used to measure acidity and basicity. Understanding pH is essential for various applications, including environmental science, medicine, and food science.

Step 1: Understand What pH Represents

• pH stands for "potential of hydrogen."
• It measures the concentration of hydrogen ions (H+) in a solution.
• The pH scale ranges from 0 to 14, where:
  • Values below 7 indicate acidity.
  • A value of 7 is neutral.
  • Values above 7 indicate basicity (alkalinity).

Step 2: Learn About Hydrogen Ions and Acidity

• Acidity is determined by the number of hydrogen ions in a solution.
• The more hydrogen ions present, the more acidic the solution is.
• Conversely, a lower concentration of hydrogen ions indicates a basic solution.

Step 3: Familiarize Yourself with the pH Scale

• The pH scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration.
  • For example, a solution with a pH of 3 is ten times more acidic than one with a pH of 4.

Step 4: Distinguish Between Acidic and Basic Substances

• Acidic substances have pH values less than 7.
• Basic substances have pH values greater than 7.
• Common examples include:
  • Acids: Vinegar (pH around 3), lemon juice (pH around 2).
  • Bases: Baking soda (pH around 9), bleach (pH around 12).

Step 5: Identify Everyday Examples of Acids and Bases

• Recognize common acids and bases in daily life:
  • Acids: Citric acid (in citrus fruits), hydrochloric acid (in stomach).
  • Bases: Soap, ammonia, and antacids.

Step 6: Be Aware of the Dangers of Strong Acids and Bases

• Strong acids and bases can be hazardous:
  • They can cause burns on contact with skin or eyes.
  • Always handle them with care and use appropriate safety equipment.

Step 7: Acknowledge Neutral Substances

• Neutral substances have a pH of 7.
• Examples include pure water and certain salt solutions.

Step 8: Understand the Importance of pH in Biology and Chemistry

• pH plays a crucial role in biological processes, including:
  • Enzyme activity: Most enzymes function optimally at specific pH levels.
  • Cellular processes: Many cellular functions are pH-dependent.

Conclusion

Understanding pH is vital for grasping concepts in biology and chemistry. By recognizing how pH affects acidity and basicity, you can better appreciate its role in various scientific fields. Next steps could include exploring how pH affects different biological systems or experimenting with pH measurement in your own projects.