MCAT General Chemistry - Introduction

Overview

• Instructor: Iman
• YouTube Channel: n/a
• Lecture: Chapter Zero - Background Information & Refresher
• Purpose: Provide essential background and important terms/concepts in chemistry for future success in the course.

Topics Covered

1. Units of Measurement
2. Temperature
3. Classification of Matter
4. Subatomic Particles
5. Atomic Mass vs. Atomic Weight

Units of Measurement

• Chemistry involves experimentation and measurement with appropriate units.
• SI System: The agreed-upon system based on the metric system.
  • 7 Base Units in the SI System:
    • Mass: Kilogram (kg)
    • Length: Meter (m)
    • Time: Second (s)
    • Temperature: Kelvin (K)
    • Electric Current: Ampere (A)
    • Amount of Substance: Mole (mol)
    • Luminous Intensity: Candela (cd)
  • Derived Units: Obtained by combining SI base units (e.g., volume, density, electric charge).
  • Volume: Derived unit for volume is cubic meter (m³).

Metric Prefixes

• Modify units for practical size representation.
  • Important Prefixes:
    • Kilo: 10^3
    • Milli: 10^-3
    • Micro: 10^-6
    • Nano: 10^-9
• Example: Easier to express human cell size in micrometers (μm) rather than meters.

Temperature

• Critical in thermodynamics and thermochemistry.
• Temperature: Average kinetic energy of particles.
  • Heat flow: From higher to lower temperature.
  • Scales:
    • Celsius: 0°C (freezing) to 100°C (boiling).
    • Fahrenheit: 32°F (freezing) to 212°F (boiling).
    • Kelvin: Absolute zero reference point, 273K (freezing).
  • Conversions:
    • Fahrenheit to Celsius: 5/9 (°F - 32)
    • Celsius to Fahrenheit: 9/5 (°C) + 32
    • Celsius to Kelvin: °C + 273

Classification of Matter

• Anything that occupies space and has mass.
• States of Matter: Solid, liquid, gas (and plasma).
  • Solids: Tightly packed particles, fixed structure.
  • Liquids: Closely packed particles, flow/change shape.
  • Gases: Widely spaced particles, move freely.
• Mixtures: Physical combinations of substances.
  • Heterogeneous: Different components visible.
  • Homogeneous (Solutions): Consistent composition.
• Pure Substances: Uniform and definite composition.
  • Elements: One type of atom (e.g., hydrogen, oxygen).
  • Compounds: Chemically bonded elements in fixed ratios (e.g., H2O).

Subatomic Particles

• Atoms: Smallest unit retaining element properties.
  • Comprised of nucleus (protons & neutrons) and electrons.
  • Protons: Positively charged, found in nucleus, ~1 amu.
  • Neutrons: Neutral, found in nucleus, ~1 amu.
  • Electrons: Negatively charged, orbit nucleus, very small mass (~1/2000 of a proton).
  • Force: Electrostatic force > gravitational force between particles.

Historical Models of Atomic Structure

• John Dalton (1803): Atoms are indivisible billiard balls.
• JJ Thompson (1898): Discovery of electrons using cathode ray tubes.
• Ernest Rutherford (1911): Nucleus is dense and positively charged (gold foil experiment).
• Niels Bohr: Electrons orbit nucleus - quantum mechanical model describes electron density probability, not exact positions.

Atomic Structure

• Atomic Number (Z): Number of protons in nucleus.
• Mass Number (A): Total protons + neutrons.
• Atomic Weight: Weighted average of all naturally occurring isotopes.
  • Isotopes: Atoms with same proton number but different neutron number.
  • Example calculation provided.
  • Atomic Mass Unit (amu): 1/12th mass of a carbon-12 atom.
  • Mole & Avogadro's Number: 1 mole = 6.022 x 10^23 entities (atoms, molecules, ions).
  • Molar Mass: Mass of 1 mole in g/mol. Example conversions demonstrated.

Ions

• Cations: Positively charged (lost electrons).
• Anions: Negatively charged (gained electrons).
  • Example problem on determining protons, neutrons, and electrons in Ni-58 and Ni-60.

Summary

• Covered crucial background concepts.
• Ready to tackle future chapters with these fundamental concepts and problem-solving strategies.

Good luck with your studies!