Unit 4 - States & Changes of Matter

Gases

  • Kinetic-Molecular Theory   * Gases are a large number of constantly and randomly moving particles   * Most of the volume of a gas is empty space   * There is no force of attraction/repulsion between particles   * All collisions are perfectly elastic     * No energy is gained/loss during collisions   * Kinetic Energy - The energy of movement [of particles]     * Average kinetic energy is directly proportional to temperature     * KE = (1/2)mv^2
  • Ideal Gas - A theoretical gas composed of randomly moving particles that don’t interact with each other   * Describes the behavior of most gases under common conditions   * Fits the description of the Kinetic-Molecular Theory   * Real gases deviating from this model under extreme conditions
  • Properties of Gases   * Compressibility     * Change in pressure → change in volume   * No fixed shape/volume     * Expands to fit container
  • Property Relationships   * Pressure & Volume have an inverse relationship   * Volume and Number of Atoms(# of moles) have a direct relationship   * Pressure and Temperature have a direct relationship     * Collision with container walls cause pressure     * More/harder collisions = more pressure     * Pressure = Force / Area   * Volume and Temperature have a direct relationship   * Pressure and Number of Atoms(# of moles) have a direct relationship
  • Diffusion - Movement of particles from high concentration to low concentration
  • Effusion - Movement of gas through a smaller opening into a larger volume   * Graham’s Law - Rate of effusion is inversely proportional to the square root of molar mass

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Liquids

  • Kinetic energy of individual particles is similar to that of the intermolecular attraction between them
  • Properties   * More dense than gases   * Have a fixed volume   * Particles aren’t fixed in place     * Can flow freely     * Viscosity - The thickness / resistance to flow of a liquid       * Directly related to intermolecular force       * Directly related to size of molecules       * Inversely related to temperature     * Takes the shape of their container   * Surface Tension - The tendency for a liquid to resist penetration     * Directly related to intermolecular force     * Surfactant - chemical compounds that can decrease surface tension   * Incompressible     * Can be used to transmit force, i.e hydraulics   * Dissolvability - When a solid, liquid, or gas becomes integrated into a host liquid     * Dissolved particles are dispersed evenly throughout the liquid     * Miscible Liquids - liquids that are able to dissolve into each other     * Immiscible Liquids - liquids that are not able to dissolve into each other
  • Intermolecular Forces   * Caused by uneven electron distribution   * Affects interactions between particles     * The stronger the force, the more kinetic energy particles need to move   * Condensation - Gas → Liquid     * Caused by intermolecular force > kinetic energy, meaning particles are pulled in towards each other   * Evaporation/boiling - Liquid → Gas     * *Evaporation is when small amounts of particles randomly gain enough energy, boiling is when the entire substance as a whole gains enough energy to change     * Caused by kinetic energy > intermolecular force, meaning particles are pulled away from each other     * Boiling point has a direct correlation w/ boiling points       * Higher intermolecular force → higher boiling point         * i.e ionic and polar covalent compounds have higher boiling points like non-polar covalent compounds   * Freezing - Liquid → Solid     * Caused by intermolecular force > kinetic energy   * Melting - Solid → Liquid     * Caused by kinetic energy > intermolecular force

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Solids and Plasmas

  • Solids   * Properties     * Low energy     * Rigid structure       * Molecules vibrates instead of move     * Fixed shape & volume   * Crystal - A solid whos components make up a highly ordered microscopic structure     * Long Range Order - A property of crystals where their atomic particles show a periodic (recurring) pattern or shape     * Lattice - A regular arrangement of atoms, molecules, etc       * Incompressible   * Amorphous Solids - Solids with particles arranged in non-uniform patterns     * Can be caused by rapid cooling such that particles do not have time to fully arrange into a crystalline structure     * Lack of long range order     * Compressible     * No definitive properties like boiling points due to changing pattern of molecules throughout     * Molecules can shift & move past each other over time
  • Plasmas   * Properties     * Composed of ionized (high-energy) particles     * EXTREMELY HOT (high temperature)     * Conducts electricity     * Compressible     * No definite volume/shape   * Examples: Lightning, Stars, Auroras, Fluorescent Lights, Ion Thrusters, Arc Welders, Plasma Displays (plasma TVs), Plasma Balls, etc   * Thermal Equilibrium - Temperature is equal to its surroundings     * Plasma can be “cold“ when:       * Their electrons break off from their nucleuses and move extremely quickly, dissipating the energy quickly       * The energy in the electrons gets converted to light       * Only a small percentage of the overall substance is ionized into a plasma
  • Comparisons   * Conduct Electricity - Plasmas always conduct electricity, only some solids do   * Density - Plasmas have low density, solids have high density   * Shape & Volume - Solids have fixed shape and volume, plasmas don’t   * Kinetic Energy - Plasmas have high kinetic energy, solids have low kinetic energy   * Composition - Plasmas are made of electrons and cations, solids are made of neutral particles or cation/anion pairs

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Phase Changes

  • Most of the phase changes are covered previously, so the only information here is going to be non-covered vocab and concepts
  • Vapor Pressure - The pressure exerted by the gas in equilibrium with a liquid   * Changes based on altitude; higher pressure → harder to boil   * Higher vapor pressure → more likely to evaporate

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Properties of Water

  • Water = H2O   * Has a total of 8 valence electrons; stable   * There are single bonds between the oxygen and each hydrogen, and two pairs of non-bonded electrons on the other side of the oxygen atom   * “Tetrahedral“ electron-domain geometry     * “bent“ molecular geometry   * Bond Angle of 104.5*
  • Properties   * Oxygen --- Hydrogen bonds are highly polar → water is a polar molecule     * Oxygen is partial negative, hydrogens are partial positive     * Allows for hydrogen bonds     * Strong solvent       * Like dissolves like → Water mostly dissolves ionic and polar covalent compounds         * Process of dissolving           * Dissociation - Water breaks an ionic compound into cations and anions           * Hydration - Water surrounds “broken apart“ substances     * Adhesion/Cohesion - Intermolecular forces; polar “stick“ to polar       * Adhesion is with other molecules, cohesion is with itself     * Strong surface tension     * High specific heat capacity
  • Uses

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