Chem 101 Week1

Matter Classification

• Matter splits into Pure Substances and Mixtures.
• Pure Substances: definite composition; either an Element or a Compound.
• Mixtures: two or more substances not chemically bonded; can be Homogeneous or Heterogeneous.
• Examples: Gold (Element), Water (Compound), Air (Mixture), Salad (Mixture), Neon (Element), Sugar (Compound), Gasoline (Mixture), Mud (Mixture).

Mixtures

• Mixture: two or more substances not chemically combined.
• Homogeneous: same proportions of components throughout the sample (e.g., sugar water).
• Heterogeneous: not uniform composition throughout (e.g., sand and water).

Pure Substances

• Pure substances: definite composition and distinct chemical properties.
• Compound: substance formed from two or more elements bonded together.
• Element: substance that cannot be decomposed into simpler substances by ordinary chemical means; examples: O_2, Na+, Ca\^2+; includes diatomic molecules.

Physical vs Chemical Changes

• Physical change: chemical composition remains the same before and after (e.g., boiling water).
• Chemical change: chemical composition changes during the reaction (e.g., combustion of methane).

Significant Figures

• Determining significant figures:
  1) All non-zero numbers are significant
  2) Trailing zeros are significant only if a decimal is involved
  3) Leading zeros are never significant
• Multiplication/Division: round to the least number of significant figures among inputs.
• Addition/Subtraction: round to the fewest decimal places among inputs.

SI Prefixes and Metric Units

• Prefix meanings (order of magnitude):
  • Giga (G): $10^9$
  • Mega (M): $10^6$
  • Kilo (k): $10^3$
  • Hecto (h): $10^2$
  • Deca (da): $10^1$
  • Base: $10^0$
  • Deci (d): $10^{-1}$
  • Centi (c): $10^{-2}$
  • Milli (m): $10^{-3}$
  • Micro (\mu): $10^{-6}$
  • Nano (n): $10^{-9}$
  • Pico (p): $10^{-12}$
• Length units: km, hm, dam, m, dm, cm, mm
• Volume units: kL, hL, daL, L, dL, cL, m