STATES OF MATTER Chemistry CP
Energy Potential Energy: Stored Energy If you heat a substance, that substance will store some of that energy in its particles Kinetic Energy: Energy of Motion
Kinetic Energy: Increases in kinetic energy result in increases in temperature Heat added to a system that is not stored as potential energy will be absorbed by the particles which will increase the particles’ kinetic energy Absolute Zero (0 K): The temperature at which the motion of particles theoretically ceases and the particles have no kinetic energy
Directly proportional to the kinetic energy of the particles Kelvin Scale: Reflects the relationship between temperature and average kinetic energy Directly proportional to the kinetic energy of the particles K = C + 273
All matter consists of tiny particles that are in constant motion Kinetic Theory All matter consists of tiny particles that are in constant motion
Intermolecular Forces Hydrogen Bonding: The large partial charge resulting in an extremely strong dipole-dipole force between hydrogen of on molecule (+) and the F, O or N of another molecule (-) One of the strongest intermolecular forces Dipole-Dipole Forces: Attractions between opposite charges of neighboring permanent dipoles Happens between polar molecules Dispersion Forces: A force of attraction between induced dipoles Induced dipoles occur when a temporary dipole occurs (the e- move to one side of an atom simply through their natural movement) Can happen between nonpolar molecules Strength
SOLID LIQUID GAS Ionic, Metallic or Molecular Bonds (Strong Bonds between atoms) Atoms, ions or molecules are packed tightly together Particles vibrate around fixed points Crystalline or Amorphous Solids Do not flow Condensed state of matter (pressure has little effect on a solid) Only slightly compressible High density Extremely slow diffusion (only occurs at surface) Definite volume Definite shape Molecules or Atoms Intermolecular forces keep the particles in a liquid close together Intermolecular forces reduce the amount of space between the particles Condensed state of matter (pressure has little effect on a liquid) Can flow (a fluid) Does not expand to fill the container Assumes the shape of the container Slow diffusion No definite shape Particles are small, hard spheres with insignificant volume Particles are far apart with empty space between them No attractive or repulsive forces between particles Motion of one particle is independent of the rest Motion of particles is rapid, constant and in straight line paths until they collide Perfectly elastic collisions (kinetic energy remains constant) Can be compressed Low density Fills container completely Assumes shape of container Rapid Diffusion No definite volume nor shape
Vacuum: An empty space with no particles and no pressure Gas Pressure: The force exerted by a gas per unit surface area of an object Caused by the collisions of the moving gas particles with an object Barometer: Device that is used to measure atmospheric pressure Atmospheric Pressure: Results from the collisions of atoms and molecules in air with objects Gasses
Units of Pressure 1 atm = 760 mm Hg = 101.3 kPa Pascal (Pa): SI unit of pressure atmosphere: Pressure required to support 760 mm Hg in a mercury barometer at 25C mm Hg: Unit on a barometer Standard Temperature & Pressure (STP): Temperature of 0C and 1 atm
LIQUIDS Vapor Pressure: A measure of the force exerted by a gas above a liquid At equilibrium: The rate of evaporation of the liquid equals the rate of condensation of the vapor
MANOMETER: Measures the vapor pressure of a contained liquid
Affect of Temperature on Vapor Pressure An increase in temperature of a contained liquid will increase the vapor pressure because the kinetic energy will increase resulting in more particles escaping the surface of the liquid.
VISCOSITY A liquids resistance to motion Liquids with stronger intermolecular forces will have higher viscosities Water’s viscosity is relatively high due to its hydrogen bonding Lower temperatures = higher viscosity
Greater in liquids with strong intermolecular forces SURFACE TENSION Imbalance of attractive forces at the surface of a liquid that causes the surface to behave as if it had a thin film across it Greater in liquids with strong intermolecular forces
SOLIDS Crystals: The particles are arranged in an orderly, repeating, 3-dimensional pattern called a crystal lattice The shape of the crystal reflects the arrangement of the particles within the solid Unit Cell: The smallest group of particles within a crystal that retains the geometric shape of the crystal
SOLIDS Amorphous Solids: Lacks an ordered internal structure Plastic, rubber, glass, asphalt
Change of State Conversion of a substance from one of three physical states of matter to another. A.k.a: Phase Change Always involves: A change in energy
Energy & State Changes Gases have the most potential energy, solids the least
VAPORIZATION: The change of state from a liquid to a gas Evaporation: Molecules at the surface of a liquid escape and enter the gas phase Boiling: When the vapor pressure of the liquid is equal to the atmospheric pressure, bubbles of gas form and escape the liquid. Evaporation rates increases with increases in temperature because the increase in energy allows more molecules to escape the surface of the liquid The molecules remaining behind in the liquid are lower in energy Boiling Point: The temperature at which the vapor pressure of the liquid becomes equal to the atmospheric pressure Normal Boiling Point: The boiling point of a liquid at a pressure of 101.3 kPa (normal atmospheric pressure)
If atmospheric pressure increases, the temperature needed to reach the boiling point will also increase. If atmospheric pressure decreases, the temperature needed to reach the boiling point will also decrease.
CONDENSATION The change of state from a gas to a liquid
FREEZING The change of state from a liquid to a solid. Freezing Point: The temperature at which the solid and liquid forms of a substance exist in equilibrium
MELTING The change of state from a solid to a liquid Melting Point: The temperature at which a solid changes into a liquid Equals: The freezing point
Sublimation: The change of state from a solid to a gas Deposition: The change of state from a gas to a solid Typically occurs with molecular solids with weak intermolecular forces.
HEATING CURVE During a state change, the temperature remains constant while the potential energy increases/decreases. This will occur until the state is completely changed and then kinetic energy will begin to increase/decrease again.
Phase Diagram Relates the state of a substance to its temperature and pressure. Triple Point: The only set of conditions at which all three phases can exist in equilibrium with one another For water, the triple point is 0.016C and 0.61 kPa/0.0060 atm