Second Semester Review

Heating Curve

Heating Curve q (heat energy) = mcT q=mHv Gas Liquid q=mHf solid q (heat energy) = mcT Where is potential energy increasing? Where is kinetic energy increasing?

Phase Diagram

Vapor Pressure Diagram Intersection of curved lines and standard pressure (bold line at 1 atm) is the normal boiling point

Intermolecular Forces Inter- means “between” or “among” Intermolecular forces hold two molecules together Ex: Water in a drop, carbon and cellulose (aka. pencil lead & paper) Weak intermolecular forces Low boiling points Most likely in gaseous state Strong intermolecular forces High boiling points Most likely in solid state

Intermolecular Forces

Boiling Point Boiling occurs throughout the liquid Boiling point occurs when Vapor Pressure=Atmospheric Pressure Higher altitudes have lower atmospheric pressure. Would the boiling point increase or decrease? Would it take a longer or shorter time to cook food?

Gas Laws Combined Gas Law If you do not have a change in one of the variables replace it with a one or omit it! Temperature must be in Kelvin! (TC + 273 = TK) Only need ONE FORMULA!!!!!!

Gas Stoichiometry Gas stoichiometry can be done using the coefficients of the balanced chemical equation and ratios

Solutions & Solubility Soluble (miscible): like dissolves like Polar or Ionic solutes dissolve in polar solvents Areas of charge are attracted to one another Ex: water, alcohol, sugar, salt Non-polar solutes dissolve in non-polar solvents No charges so there is no attraction Ex: oils, gasoline, diatomic molecules (H O F Br I N Cl) Insoluble (immiscible): do not dissolve in each other Polar and non-polar Ex: oil and water

Solubility Curve Above the curve would be supersaturated if completely dissolved (in solution) The curve itself is at saturation Below the curve indicates unsaturated solutions Negative (downward) slope indicates a gas

Concentration Molarity (M): # mol solute dissolved in 1 L of solution

Heat Energy (Enthalpy) Heat, which is represented by the symbol q, is energy that is in the process of flowing from a warmer object to a cooler object. When the warmer object loses heat, its temperature decreases. When the cooler object absorbs heat, its temperature rises. H : Tells us if a reaction is endothermic or exothermic (measure of change in energy)

Exothermic Reaction Energy flows from system to surroundings

Endothermic Reaction Energy Flows from Surroundings to System

Factors that Effect Reaction Rate Concentration of Reactants The more particles, the more collisions As concentration increases, rate increases

Factors that Effect Reaction Rate Temperature of Reactants As temperature increases, particles move faster; there are more high-energy collisions

Factors that Effect Reaction Rate Particle Size (surface area) For solids, breaking up big pieces increases surface area, increasing rate by having more places for the molecules to interact

Factors that Effect Reaction Rate Pressure – Gases only! As pressure increases the concentration increases, so you will have more collisions

Factors that Effect Reaction Rate Catalysts – compounds added to speed up reaction but not used in the reaction. Lowers activation energy but does not change ΔH Examples: enzymes in your body, catalytic converters (Pt, Rh, or Pd plates that convert NO → N2 + O2 and CO → CO2)

Factors that Effect Reaction Rate Inhibitors Compounds added to a reaction that slow it down Examples: Lead in diesel, preservatives in food.