Lecture Notes: Chapter 3 - Water and pH

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• Complete your lab at your scheduled time in Univ Virtual.
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  • Cancelled classes from 2 PM onward.
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• "Realize It" chemistry module open until September 3; free access ends August 31.

General Information

• Labs are accessible early this week due to the upcoming holiday.
• For lab access or technical issues, contact Professor Michelle Urain.
• Campus internet issues may affect lab access.

Exam and Course Material

• Exam 1 covers Chapters 2, 3, and 4.
• Focus currently on Chapter 3 - Water and pH.

Properties of Water

1. Polarity and Hydrogen Bonding

   • Water molecules are polar and form hydrogen bonds.
   • Responsible for properties like cohesion, adhesion, and surface tension.

2. Specific Heat

   • Water resists temperature changes due to hydrogen bonds.

3. Heat of Vaporization

   • Water has a high heat of vaporization, requiring significant energy to change from liquid to gas.

4. Density and Freezing

   • Ice is less dense than liquid water due to air trapped in ice crystals.

5. Solvent Properties

   • Water dissolves polar substances due to its polarity.

Acids, Bases, and pH

• Definitions

  • Acid: Increases hydrogen ions (H+) in solution.
  • Base: Absorbs hydrogen ions or donates hydroxide ions (OH-).

• Logarithmic pH Scale

  • Scale ranges from 0 (strong acid) to 14 (strong base); 7 is neutral.
  • Each unit change corresponds to a tenfold change in H+ concentration.

• Equations

  • pH = -log[H+]
  • pOH = -log[OH-]
  • pH + pOH = 14

Buffers

• Substances that moderate pH changes in solutions.
• Blood pH is maintained between 7.35 and 7.45.
• Proteins act as buffers via functional groups.

Important Concepts and Examples

• Hydrophilic vs. Hydrophobic

  • Hydrophilic substances dissolve in water; hydrophobic do not.

• Examples of pH in Substances

  • Stomach acid: pH 1-2
  • Soda: Approx. pH 3
  • Seawater: Slightly basic, around pH 8.

Next Class Preview

• Continued discussion on solving pH-related problems.
• Review of logarithmic calculations for pH and concentration.