Chem 151 Lecture Notes - Chapter 1

Introduction

• Professor: Dr. Feiler
• Course Material: Slides from "Introductory Chemistry" by Nivaldo Tro.
• Resources: Free text available online and slides on Canvas.

Definition of Chemistry

• Study of matter by understanding what it is made of: atoms and molecules.
• Everything (e.g., humans, tables) is made of atoms.
• Atoms are found in the periodic table.

Elements and Origin

• Periodic Table: ~100 elements (e.g., Carbon, Nitrogen, Oxygen).
• Big Bang Theory: Universe began ~13.8 billion years ago.
  • Initial state: Primarily hydrogen atoms.
  • Gravity led to formation of stars from hydrogen.
  • Nuclear Fusion in Stars: Hydrogen atoms fuse to form heavier elements like helium, carbon, oxygen, etc.
  • Supernova: Star explodes, spreading heavier elements into space.
• Planet Formation: Elements form planets such as Earth.

Composition of Earth, Universe, and Human Body

• Earth Composition:
  • Most abundant elements: Iron (34.6%), Silicon, Oxygen, Magnesium.
  • Rocks contain Silicon Dioxide (SiO₂).
• Universe Composition:
  • 74% Hydrogen, 24% Helium.
• Human Body Composition:
  • Major elements: Oxygen, Hydrogen, Carbon (18%), Nitrogen, Calcium, Phosphorus.

Atoms and Molecules

• Atoms: Very small, require sensitive instruments to observe.
• Molecules: Two or more atoms bonded together.
  • Water Molecule: H₂O (Oxygen and Hydrogen).
  • Carbon Dioxide: CO₂ (Carbon and Oxygen).

Examples of Molecules in Everyday Items

• Coca-Cola: Contains water, carbon dioxide, sugar, caffeine.
• Graphite: Carbon atoms used in pencils.
• DNA: Composed of Carbon, Nitrogen, Oxygen, Hydrogen, Phosphorus.

Scientific Method

• Key Concepts:
  • Observations: Recordings of measurements.
  • Hypothesis: Tentative interpretation of observations.
  • Law: Hypothesis proven true after repeated experiments.
  • Theory: Explanation of why a law is true.
• Example - Zeroth Law of Thermodynamics:
  • Heat transfers from hot to cold objects.
  • Experiment: Measure temperature changes.
  • Observation: Heat moves from hotter to cooler objects.
  • Theory: Atoms move more at higher temperatures, transferring energy when in contact.

Conclusion

• Importance of understanding atoms and molecules in chemistry.
• Introduction to the scientific method and how it helps explain natural phenomena.
• Reminder to read and review chapter materials independently.