Energy in Chemical & Physical Changes. Thermochemistry. Study of changes that accompany chemical reactions and phase changes The Universe is considered to be made of 2 parts: 1. System: part that contains the reaction or process 2. Surroundings: everything else. ENERGY.
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Energy in Chemical & Physical Changes
1. System: part that contains the reaction or process
2. Surroundings: everything else
2 types of energy
C8H18 + O2 H2O + CO2 + Energy
4Fe + 3 O2 2 Fe2O3 + 1625 kJ OR
4Fe + 3 O2 2 Fe2O3H = - 1625 kJ
27kJ + NH4NO3(s) NH4(aq)+1+NO3(aq)-1 OR
NH4NO3(s) NH4(aq)+1+ NO3(aq)-1H = + 27 kJ
1. amount of substance (mass)
2. Temperature change
3. type of material (specific heat)
1 cal= 4.184 J
1kcal = 1000 calories.
Greater Thermal Energy
Water has a specific heat of 4.184 J/gC.
Iron(Fe) has a specific heat of .449 J/gC.
Gold (Au) has a specific heat of .129 J/gC.
c= specific heat
q = heat in joules or galories
T = change in temperature = Tf – Ti
q = m x c x T
For water, Hfus = 334 J/g
q = Hfus x mass
For water, Hsolid = -334 J/g
q = Hsolid x mass
For water, Hvap= 2260 J/g
q = Hvap x mass
For water, Hcond = -2260 J/g
q = Hcond x mass