REACTIONS Energy in Reactions Some chemical reactions release heat to the surroundings These are called EXO THERMIC reactions Heat EXITS the reaction Some chemical reactions absorb ID: 575258
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Slide1
Exothermic & Endothermic REACTIONS
Energy in ReactionsSlide2
Some chemical reactions
release
heat to the surroundingsThese are called EXOTHERMIC reactionsHeat EXITS the reactionSome chemical reactions absorb heat from the surroundingsThese are called ENDOTHERMIC reactionsHeat ENTERS the reaction
Energy in ReactionsSlide3
All substances have a type of chemical potential
:
The total energy (J or kJ) contained in a system Chemical potential energy in a substanceThe symbol for enthalpy is HΔH = Hproducts – HreactantsEnergy in ReactionsSlide4
An
exothermic reaction
converts the enthalpy stored in a substance into HEAT which is released to the surroundingsN2 + 3H2 2 NH3+ heat Exothermic Reactions
Has
higher
enthalpy
Has
lower
enthalpySlide5
Exothermic Enthalpy Diagram
Products
Reactants
Enthalpy (H)
Reaction Proceeds
ΔH
is NegativeSlide6
1.
The “heat term” written on the
PRODUCTS sideN2 + 3H2 2 NH3 + 46.2 kJ2.
ΔH written beside the equation is
NEGATIVE
.
N
2
+ 3H
2 2 NH3
ΔH = - 46.2 kJExothermic ReactionsSlide7
Exothermic Reactions:
ΔH is
negativeProducts are lower than reactants on the enthalpy diagramHeat is released to the surroundingsIn Summary…Slide8
An endothermic reaction
absorbs
heat from the surroundings and converts into enthalpy2C + 2 H2 + heat C2H4 Endothermic Reactions
Has
higher
enthalpy
Has
lower
enthalpySlide9
Endothermic Enthalpy Diagram
ΔH is POSITIVE
Products
Reactants
Enthalpy (H)
Reaction ProceedsSlide10
1. The “heat term” written on the
REACTANTS
side.2 C + 2H2 + 52.3 kJ C2H42. ΔH written beside the equation is POSITIVE
.
2 C + 2 H
2
C
2
H4 ΔH = + 52.3 kJ
Endothermic ReactionsSlide11
Endothermic Reactions:
ΔH
is positiveProducts are higher than reactants on the enthalpy diagramHeat is absorbed from the surroundingsIn Summary…Slide12Slide13Slide14
In Class Work
Please collect the Endo/
Exo Worksheet from the front of the room, finish this worksheet by next classNext Class: Begin Stoich