Chem Unit 1

CHEM Module 1 — Lecture 2

Scientific Method

  • Observation → hypothesis → experiment → theory

  • Hypothesis = testable explanation

  • New evidence can cause theories to be changed

Matter & Properties

  • Matter = has mass + takes up space

  • Physical property = observed without changing substance

  • Chemical property = ability to react/form new substance

  • Intensive = does NOT depend on amount (density, temperature)

  • Extensive = DOES depend on amount (mass, volume)

  • Physical change = no bonds formed/broken

  • Chemical change = bonds formed/broken

SI Units

  • Length = m

  • Mass = kg

  • Time = s

  • Temperature = K

  • Amount = mol

Dimensional Analysis

  • Use conversion factors so unwanted units cancel

  • Final units should match what question asks

Moles

  • 1 mol = 6.0221×10236.0221×10^{23} particles

  • Avogadro's number = 6.0221×1023 mol−16.0221×10^{23}\ mol^{-1}

  • Molar mass (M) = mass of 1 mol in g/mol

Main Formulas

  • Moles: n=m/Mn=m/M

  • Particles: n=#particles/NAn=\#particles/N_A

  • Concentration: C=n/VC=n/V

  • Density: d=m/Vd=m/V

  • Gas: PV=nRTPV=nRT

STP

  • 273.15 K

  • 100.000 kPa

  • 1 mol gas = 22.711 L

BIG IDEA: Most chemistry conversions go given → moles → wanted quantity.