Thermochemistry

energy

ability to work or produce heat

potential energy

based on the composition or position of an object

kinetic energy

energy of motion

law of conservation of energy

states that in any chemical reaction or physical process, energy can be converted from one form to another, BUT neither CREATED NOR DESTROYED

chemical potential energy

energy stored within bonds

* sugar and fats have this

combustion reaction

breaking down of sugars and fats, much of the energy is released as heat

heat

energy in the process of flowing from a WARMER —> COOLER object

* q
* (delta)H : heat of reaction

joule (J)

SI unit of heat and energy

1 kJ

1000 j =

1 Cal (kilocalorie)

1000 calories =

4\.184 joules

1 cal =

specific heat of water

4\.184 j/g°C

specific heat

amount of heat required to raise the temperature of 1 gram of a substance by 1 °C

* c

q = mc(delta)T

formula to calculate heat released or absorbed

Tf-Ti

(delta)T

calorimeter

insulated device used for measuring amount of heat absorbed/released during a chemical of physical process

* can determine the specific heat of an unknown metal

thermochemistry

study of heat energy accompanying chemical reactions and phase changes

thermochemistry equation

balanced equation including energy change

* expressed as change of enthalpy

enthalpy (heat) of vaporization

heat required to vaporize (boil or condense) 1 mol of a liquid

enthalpy (heat) of fusion

heat require to melt or freeze 1 mol of a solid

heating/cooling curve

graph showing phase changes as temperature increases/decreases

rate

speed of a chemical change over an interval of time

collision theory

atoms, ions, and molecules must collide in order to react

* however, NOT ALL COLLISIONS FORM REACTIONS

Intermediate substance/activated complex/transition state

short lived period when once molecules collide, the energy is the highest

* highly unstable

activation energy

minimum energy required to form activated complex.

* directly influences rate or reaction

reactant nature (factor changing rate)

reactivity directly influences rate of reaction

concentration (factor affecting rate)

\# of particles in a given volume directly influences rate

Surface Area (factor affecting rate)

directly affects rate because of increased/decreased collision frequency

* particle SIZE and SA are opposite

temperature (factor affecting rate)

directly affects rate by increasing kinetic energy, both collision FREQUENCY and ENERGY are affected

* ONLY factor changing energy

catalyst

substance that increases reaction rate without being used up

* lowers activation energy = more successful collisions

intermolecular forces

when temperature is stagnant during a phase change, the energy is being used to break __

enthalpy of combustion

Complete burning of 1 mol of a substance

exothermic

products have LESS energy than reactants

(delta)E

Energy released

increases surface area

grinding a substance into a powder ____, which will increase the rate of reaction.