MCAT General Chemistry - Chapter 0: Background Information

Introduction

Presenter: Iman
Platform: YouTube channel
Content: New MCAT General Chemistry Playlist
Focus of Chapter 0: Background information and key concepts.
- Units of measurement
- Temperature
- Classification of matter
- Subatomic particles
- Atomic mass vs. atomic weight
- Introduction to stoichiometry

Importance: Chemistry involves measurements; units are crucial for communication.
System Used: SI (International System of Units) based on the metric system.
SI Base Units: 7 base units
- 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).
Metric Prefixes: Modify units to express different scales (e.g., kilo (10^3), milli (10^-3), micro (10^-6), nano (10^-9)).

Definition: Correlates with average kinetic energy of particles.
Scales Used: Fahrenheit, Celsius, Kelvin.
- Celsius: Freezing = 0°C, Boiling = 100°C
- Fahrenheit: Freezing = 32°F, Boiling = 212°F
- Kelvin: Absolute zero = 0K, Freezing point of water = 273K
Conversions:
- °C = (5/9) * (°F - 32)
- °F = (9/5) * °C + 32
- K = °C + 273
Thermometers: Measure temperature by the expansion/contraction of liquids like mercury.

Definition: Anything that occupies space and has mass.
States: Solid, liquid, gas
Matter Types:
- Mixtures (Physical combinations)
  - Heterogeneous: Visible different components (e.g., sand and water)
  - Homogeneous (Solutions): Consistent composition (e.g., salt dissolved in water)
- Pure Substances:
  - Elements: Consist of one type of atom, cannot be decomposed (e.g., hydrogen, carbon).
  - Compounds: Formed from two or more elements in fixed ratios (e.g., water).

Atom: Smallest unit of an element, made of nucleus (protons, neutrons) and electrons.
- Protons: Positively charged, mass ≈ 1 amu, located in nucleus
- Neutrons: No charge, slightly larger mass than protons, located in nucleus
- Electrons: Negatively charged, move around nucleus, mass ≈ 1/2000 of a proton
Hierarchy of Matter: Mixtures → Pure substances → Elements and compounds → Atoms → Subatomic particles
Quarks: Fundamental particles making up protons and neutrons (Not needed for MCAT).

Key Numerical Descriptors:
- Atomic number (Z): Number of protons, defines the element.
- Mass number (A): Sum of protons and neutrons.
- Atomic weight: Weighted average mass of an element's isotopes.
Isotopes: Variants of elements with same number of protons but different neutrons.
Calculations: Atomic weight = Σ (Mass of isotope * Natural Abundance).

Atomic Mass Unit (AMU): Standard unit to quantify mass of atoms/molecules = 1/12 of C-12 atom.
Mole: Measures amount of substance; 1 mole = 6.022 * 10^23 entities (Avogadro's number).
Molar Mass: Mass of one mole of substance (element/compound) expressed in g/mol.
Conversions:
- Particles ↔ Moles: Divide/multiply by Avogadro's number
- Moles ↔ Mass: Multiply/divide by molar mass
- Particles ↔ Mass: Two steps (Divide by molar mass, multiply by Avogadro's number or vice versa)

Convert Particles to Mass: 3.11 * 10^23 particles of argon → Calculate mass.
- Steps: Divide by Avogadro's number, multiply by molar mass.
- Result: Mass = 19.75g
Determine Subatomic Particles in Atoms/Ions: Nickel-58 and Nickel-60^2+.
- Nickel-58 (neutral):
  - Protons = 28
  - Neutrons = 30 (mass number - atomic number)
  - Electrons = 28
- Nickel-60^2+ (cation):
  - Protons = 28
  - Neutrons = 32 (mass number - atomic number)
  - Electrons = 26 (28 protons - 2 electrons)

Summary: Covered fundamental concepts in General Chemistry to build foundation for future chapters.
Next Steps: Dive deeper in subsequent chapters into atoms, subatomic particles, and chemical behaviors.
Encouragement: Engage with content, ask questions, and stay motivated.