thermochem

hermochemistry

study of heat change that accompanies physical changes and chemical reactions

Heat

energy transfer between samples of matter

Heat of Fusion

amount of energy per gram needed to change from solid to liquid at its melting point

Temperature

average amount of kinetic energy in an object

Heat of Vaporization

amount of energy needed to change from liquid to gas at its boiling point

Joule

si unit for energy

Endothermic

reaction gains energy from surroundings

Specific Heat Capacity

amount of heat needed to raise 1 gram of a substance 1C

Hess’s Law

the overall enthalpy of a reaction is equal to the sum of every step reaction deltaH

Enthalpy

the amount of energy absorbed or lost by a reaction

Exothermic

reaction releases energy into surroundings

Hess’ law rules

1) compounds on both sides of the arrow evenly cancel each other out

2) if a step reaction has to be reversed to match the overall, the sign of delta H is reverse

3) in order to match coefficients of the overall equation, multiply every formula and deltah by the same number

phase change formula

e=mh

specific heat equation

e=cp(m)deltaT

physicalchange

heat is tranferred from the substance with higher temp to substance with lower temp

chemical change

heat change based on what reactants and products are in the reactions

system

all substances that are the current focus of measurement

surroundings

everything not included in the system

water cp

4.184

ice cp

2.06

water vapor cp

1.87

gold cp

.129

ethanol cp

2.44

iron cp

.449

mercury cp

.14

lead cp

.129

carbon cp

.647

aluminum cp

.897

exothermic

reaction lowers enthalpy by releasing heat into surroundings (product)

endothermic

reaction raises enthalpy by gaining heat energy from surroundings (reactant)

enthalpy

internal energy of a system (delta H)