CHEM 16

• Chemistry describes matter (its properties, the changes it undergoes, the energy that accompanies those changes)
• Matter


  Anything that has mass and occupies space
• Energy


  The capacity to do work or to transfer heat
• Potential energy


  Energy due to the position of the object or energy from a chemical reaction
• Kinetic energy


  Energy due to the motion of the object
• Potential and kinetic energy can be interconverted
• Properties of Matter

  • Physical property: exhibited by a substance by itself, without changing into or interacting with another substance
  • Chemical property: exhibited by a substance as it changes into or interacts with another substance
• Physical change

  When a substance alters its physical form, not its composition
• Chemical change


  When a substance is converted into a different substance
• States of Matter

  • Solid
  • Liquid
  • Gas
  • Plasma
  • Liquid-Crystal
  • Bose-Einstein Condensate
• Measurement of Matter

  • Accuracy: closeness of the obtained measurement to the true value
  • Precision: closeness of obtained measurements to each other
• Significant Figures

  • All non-zero numbers are significant
  • Leading zeros are never significant
  • Trailing zeroes may be significant
• Significant Figures

  • Non-zero numbers are significant
  • Leading zeros are never significant
  • Trailing zeroes may be significant
  • Embedded zeroes are always significant
• Examples of significant figures

  • 452.58 → 5 significant digits
  • 0.000012 → 2 significant digits
  • 120 apples → indeterminate number of significant digits
  • 6.245 × 10^5 → 4 significant digits
  • 703.20503 → 8 significant digits
• Significant Figures on Addition/Subtraction

  The number of decimal places in the sum/difference should be equal to the lowest number of decimal places (D.P.) in the addends/minuend and subtrahend
• Significant Figures on Multiplication/Division

  The number of significant figures in the product/quotient should be equal to the lowest number of significant figures (S.F.) in the factors/dividend and divisor
• Physical Properties

  • Length
  • Volume
  • Mass
  • Density
  • Percent Composition
  • Specific Gravity
  • Heat
  • Temperature
  • Conversion of Temperature
• Units of Measurement

  • Length - meter (m)
  • Mass - kilogram (kg)
  • Time - second (s)
  • Electric current - ampere (A)
  • Temperature - kelvin (K)
  • Luminous intensity - candela (cd)
  • Amount of substance - mole (mol)
• Composition of Matter

  • Pure Substances
  • Elements
  • Compounds
  • Mixtures
  • Homogeneous Mixtures
  • Heterogeneous Mixtures
• Antoine Lavoisier: 'Law of Conservation of Mass: the total amount of matter (mass) remains constant regardless of any chemical change; matter cannot be created nor destroyed'
• Joseph Louis Proust: 'Law of Definite Composition: pure samples of a compound will be composed of the same elements with constant mass fractions'
• John Dalton: 'Law of Multiple Proportions: when two elements, A and B, form more than one compound, the ratio of the masses of B that combine with a given mass of A in each compounds can be expressed as small whole numbers
• Regardless of any chemical change, matter cannot be created nor destroyed
• John Dalton: 'Law of Multiple Proportions: When two elements, A and B, form more than one compound, the ratio of the masses of B that combine with a given mass of A in each compound can be expressed as small whole numbers'
• Law of Conservation of Energy: 'Energy cannot be created or destroyed in a chemical reaction or in a physical change. It can only be converted from one form to another'
• Dalton's Atomic Theory: 'An element is composed of extremely small indivisible particles called atoms. Atoms cannot be created, destroyed, or transformed into atoms of another element. All atoms of a given element have identical properties (e.g. mass), which differ from those of other elements. Compounds are formed when atoms of different elements combine with each other in small whole number ratios. Relative numbers and kinds of atoms are constant in a given compound'
• Atomic Models

  • Democritus: Hard Sphere Model
  • J.J. Thompson: Plum-pudding model, Discovered electrons in 1897, Used cathode ray tubes
  • Neils Bohr: Planetary Model
  • Schrodinger: Electron Cloud Model
  • Rutherford: Gold Foil Experiment, Prior to his gold foil experiment, he first discovered α, β, and γ radiation, Discovered the nucleus and proton and proposed the existence of a nucleus
  • Millikan: Oil drop Experiment, Discovered the mass of an electron in 1909
• Atomic Symbol and Isotopes of the Elements


  • Isotopes: same Z, different A
  • Isobars: atoms of different elements having the same atomic mass but different atomic number
  • Isotones: elements having the same number of neutrons
  • Number of neutrons = A - Z
  • Number of electrons = Z - charge
  • Atomic weight (given % abundance of isotopes) = (%abundance of Isotope A)(Mass of Isotope A) + (%abundance of Isotope B)(Mass of Isotope B) + ...
• Atom


  Smallest particle of an element that maintains its chemical identity through all physical and chemical changes
• Molecule


  Smallest particle an element or compound that can have a stable independent existence
• Ions


  When an atom or molecule gains or loses multiple or single electrons, they gain extra charge that makes their properties entirely different from the original atom or molecules
• Fundamental Particles

  • Electrons (e-) = 0.00054858 amu
  • Protons (p+) = 1.0073 amu
  • Neutrons (no)= 1.0087 amu
  • 1 amu = 1.66054 x 10-24 g
• Basic Properties of Light

  Wave Nature of Light: Relationship between frequency, v (number of cycles per second) and wavelength, λ (distance traveled by wave per second): c = v * λ, where c = 3.00 •1O^ m/s, v = frequency or the number of crests or troughs that pass a given point per second, Frequency and wavelength are inversely proportional; the higher the frequency, the shorter the wavelength, Amplitude (height of the crest of each wave) describes the intensity of the light, Evidence: diffraction pattern produced when light is passed through slits
• gamma < x-ray
• Frequency and wavelength are inversely proportional; the higher the frequency, the shorter the wavelength
• Amplitude


  Describes the intensity of the light
• Evidence: diffraction pattern produced when light is passed through slits
• Visible region of light

  • ROYGBV
• The 3 Phenomena that the wave model can’t explain: 1. Emission of light from hot objects or black-body radiation 2. Emission of electrons from metal surfaces on which light shines or the photoelectric effect 3. Emission of light from electronically excited gas atoms to form emission spectra
• When solids are heated, they emit radiation (Black-Body Radiation)