Thermal chemistry is study of the transfer of heat in chemical reactions and physical changes. The student will be able to; 1. compare, contrast, analyze Potential Energy diagrams 2. interpret numerical heat values written in chemical reactions

Some reactions are: exothermic = get hot = released heat endothermic = get colder = absorbed heat The energy of the chemical reaction is displayed on a potential energy diagram.

Energy may be consumed or produced (exothermic or endothermic) in a chemical reaction. Enthalpy: change in energy delta H j/mol delta E j/mol enthalpy heat of reaction Activation Energy: E a the energy needed to get the reaction started

How is the height of the curve related to the ease a reaction will occur? What would the potential energy graph look like for a rapid reaction? What would happen if amount <E a were supplied?

Heat expressed in reactions. l.E- released H is negative, E- absorbed H is positive. 2.If H is + and written with products then exothermic 3C + Fe 2 O 3 3CO + 2Fe kj 3.If H is + and written with reactants then endothermic 2H 2 0(l) kj2H 2 (g) + O 2 (g) 4.If H is – and written with products then endothermic 3C + Fe 2 O 3 3CO + 2Fe – kj

Reaction Rate: “How fast the reaction proceeds” Reaction Rate depends on : 1. number of molecule collisions 2. efficiency of the collisions 5 factors can effect the rate of reaction: l. Nature of reactants 2. surface area ( big chunk vs. powder ) 3. temperature ( hot or cold ) 4. concentration 5. catalyst ( only effects rate does not participate in reaction…can recover.)

Thermal chemistry is study of the transfer of heat in chemical reactions and physical changes. The student will be able to; 1. compare, contrast, analyze Potential Energy diagrams 2. interpret numerical heat values written in chemical reactions

Entropy The student will : have a conceptual understanding of entropy and its application toward reactions. be able to determine the direction of entropy when given a chemical reaction.

Entropy: a measure of degree of randomness of the molecules. Delta S j/mol*K or kj/mol*K “most reactions in nature are toward disorder” Organized disorganized Entropy increases as phase change occurs from solid to liquid to gas SLgSLg Increase in entropy + delta S …..more crazy random (favored) Decrease in entropy - delta S ……more organized You can tell entropy by looking at the phases of the reaction ws. 17.8

Entropy The student will : have a conceptual understanding of entropy and its application toward reactions. be able to determine the direction of entropy when given a chemical reaction.