Matter and Its Properties – General Chemistry 1

Chemistry & Scientific Method

• Chemistry: study of matter and the changes it undergoes.
• Scientific method stages:
  • Observation: qualitative (descriptive) & quantitative (numerical).
  • Hypothesis: tentative explanation.
  • Law: constant relationship stated concisely.
  • Theory: well-substantiated unifying principle.

States of Matter

• Solid: tightly packed particles, fixed shape/volume, very low kinetic energy.
• Liquid: close particles, indefinite shape, nearly incompressible, moderate kinetic energy.
• Gas: widely spaced particles, no fixed shape/volume, highly compressible, high kinetic energy.
• Plasma: ionized, extremely high kinetic energy, dominant state in universe.

Composition of Matter

• Substance: constant composition & distinct properties.
  • Element: cannot be chemically broken down.
  • Compound: atoms of ≥2 elements in fixed proportions.
• Mixture: physical combination retaining individual identities.
  • Homogeneous (solution): uniform composition.
  • Heterogeneous: non-uniform; includes suspensions (settle) & colloids (dispersed phase + medium).

Separation Techniques (Core Principles)

• Filtration: separates suspension solid (residue) from liquid (filtrate).
• Sieving: separates solids by particle size.
• Separatory funnel: separates immiscible liquids (density difference).
• Decantation: pours off supernatant after settling.
• Centrifugation: accelerates settling using centrifugal force.
• Magnetic separation: removes magnetic metals.
• Sublimation: solid → gas directly; isolates sublimable solids.
• Distillation: separates miscible liquids by different boiling points.
• Chromatography: separates components via differential affinity.
  • Paper modes: descending, ascending, circular.
  • Retention factor Rf = \frac{\text{distance solute}}{\text{distance solvent}} (0–1 scale; higher Rf ⇒ greater solubility/lower stationary-phase attraction).

Adsorption vs Absorption

• Adsorption: surface adhesion of particles (e.g., activated carbon).
• Absorption: uptake into bulk phase (e.g., water into paper towel).

Properties of Matter

• Physical properties: observed without altering composition.
  • Intrinsic (intensive): independent of amount (e.g., density).
  • Extrinsic (extensive): depend on amount (e.g., mass).
• Chemical properties: describe ability to undergo chemical change.

Changes of Matter

• Physical change: form/state alters; composition unchanged.
• Chemical change: new substance formed; indicators include energy exchange, gas, precipitate, odor, temperature, or color change.