Basic Concepts of Chemistry

Matter

• Categories:
  • Pure Substances
    • Contain the same type of particles.
    • Examples: Iron sheet, Sodium chloride.
    • Exam Tip: Elements and compounds are pure substances because they are made of one type of particle.
  • Impure Substances
    • Contain different types of particles.
    • Examples: Salt solution, Salad.
    • Exam Tip: Mixtures are impure because they are made of different types of particles.
    • Common mixtures in MCQs: Air, Seawater, Solutions, Suspensions, Colloids, Alloys like steel.

Properties of Matter

• Physical Properties
  • Can be observed without changing the substance.
  • Trick: "Moving When Should Come Late"
    • M = Mass
    • V = Volume
    • S = Shape
    • C = Color
    • L = Length
  • Include changes like: Melting, Boiling, Evaporating, Sublimating, Condensing.
• Chemical Properties
  • Observed when a substance changes its state.
  • Trick: "Amir Bhai Will Come"
    • A = Acid
    • S = Air
    • B = Base
    • W = Water
    • C = Chemical

Physical Quantities

• Definition: Anything measurable.
• Categories:
  • Base Physical Quantities:
    • Fundamental quantities like Length, Time.
    • Trick: "Lisa Mem Turns To A Left Edge"
      • L = Length, M = Mass, T = Time, T = Temperature, S = Amount of Substance, L = Light Intensity, E = Electric Current.
  • Derived Physical Quantities:
    • Derived from base quantities, e.g., Speed = Length/Time.
  • International System of Units (SI):
    • Established in 1960 for 7 base quantities.
    • SI Units: Meter, Kilogram, Second, Kelvin, Mole, Candela, Ampere.
  • Mass vs Weight:
    • Mass: Amount of matter.
    • Weight: Force between Earth and object.
    • Units: Mass in kg, Weight in Newton.

Prefixes

• Mnemonics added to units for multiples/fractions.
• Positive Prefixes:
  • Trick: "Dad Has Kept My Great Trick"
    • D = Deca, H = Hecto, K = Kilo, M = Mega, G = Giga, T = Tera
• Negative Prefixes:
  • Trick: "That Can Make Me Nice Person"
    • D = Deci, C = Centi, M = Milli, M = Micro, N = Nano, P = Pico

Scientific Notations

• Used for writing very large or small numbers concisely.
  • Example: Earth's mass = (6 \times 10^{24}) kg

Significant Figures

• Important digits in measurements.
• Finding Significant Figures:
  • Non-decimal: Go from first non-zero to last non-zero digit.
  • Decimal: Go from first non-zero to last digit.

Accuracy and Precision

• Accuracy: Closeness to actual value.
  • Example: Accurate = measurement matches actual.
• Precision: How close measurements are to each other.
  • Example: High precision = measurements are close, even if not accurate.

Dimensional Analysis

• Converting units.
  • Example: 3045 m to km, 35°C to Kelvin.

Laws of Chemical Combination

• Law of Conservation of Mass: Mass is conserved in reactions.
• Law of Definite Proportion: Elements combine in fixed mass ratios.
• Law of Multiple Proportion: Elements combine in whole number ratios.
• Gay-Lussac's Law: Pressure is proportional to temperature.
• Avogadro's Law: Volume proportional to number of moles at constant T & P.

Mole and Avogadro's Number

• Mole Concept: A measure of substance amount; 1 mole = 6.023 x (10^{23}) particles.
• Molar Mass: Mass of one mole of a substance.

Molarity and Molality

• Molarity (M): Moles of solute per liter of solution.
• Molality (m): Moles of solute per kg of solvent.

---

These notes cover key concepts and personal tricks for understanding the basic principles of chemistry.