4.1 Energy changes in chemical reactions Flashcards
heat vs enthalpy, heat capacity, calorimetry
heat (q) is…
total energy absorbed or released DURING A REACTION
measured in Joules
enthalpy (H) is…
how much energy one particular chemical species contains
measured in kJ
heat (q) equation
q = mCΔT
enthalpy of reaction (ΔH) equation
ΔH = -q/n
heat capacity is…
amt. of heat energy required to change the substance temperature by one degree
Units are J g-1 K-1
1 megajoule (MJ) =
1,000 kJ
1 kJ =
1,000 J
indicators of chemical reactions (5)
permanent colour change, odour, gas product, formation of precipitate, release or absorption of energy
if ΔH < 0, reaction is…
exothermic
if ΔH > 0, reaction is…
endothermic
bond breaking…
REQUIRES energy
energy is transferred from particle to particle in collision
bond forming…
RELEASES energy
& increases kinetic energy of particles
what is calorimetry
measure of heat changes in systems
equipment for combustion calorimetry
retort stand, clamp, boss head
a spirit burner under a copper can with water in it
a thermometer sticking into the water
equipment for solution calorimetry
insulated cup and stopper
thermometer and stirrer in the solution
