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ENERGY CHANGES IN REACTIONS. HEAT. DEFINITION: ENERGY THE ABILITY TO DO WORK. TYPES OF ENERGY. RADIANT ENERGY : DEF: LIGHT (LIGHT USUALLY ISN’T REFERRED TO AS “HEAT” BUT IT SHOULD BE INCLUDED IN THIS DISCUSSION) DIFFERENT COLORS HAVE DIFFERENT ENERGIES - PowerPoint PPT Presentation
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ENERGY CHANGES IN REACTIONS
HEAT
DEFINITION: ENERGY THE ABILITY TO DO WORK
TYPES OF ENERGY
RADIANT ENERGY:DEF: LIGHT(LIGHT USUALLY ISN’T REFERRED TO AS “HEAT” BUT IT SHOULD BE INCLUDED IN THIS DISCUSSION)DIFFERENT COLORS HAVE
DIFFERENT ENERGIESINFRARED < RED < PURPLE < ULTRAVIOLET
TYPES OF ENERGY
KINETIC ENERGY:DEF: ENERGY BECAUSE OF MOTIONTHIS IS THE ENERGY YOU FEEL WHEN THE WEATHER IS “HOT”HIGHER TEMPERATURE MEANS
THE PARTICLES ARE MOVING FASTER
(THERE IS NO SUCH THING AS “COLD”… COLD IS JUST THE ABSENCE OF HEAT)
TYPES OF ENERGY
POTENTIAL ENERGY:DEF: ENERGY BECAUSE OF POSITION
(OF THE ATOMS IN A COMPOUND)THIS IS THE ENERGY STORED IN A CHEMICAL IE. DYNAMITE & GASOLINE HAS A
LOT OF ENERGY BUT DON’T FEEL HOT
(Name a food that has a lot of energy/calories but is COLD.)
POTENTIAL ENERGY
POTENTIAL ENERGY IS FREQUENTLY SHOWN ON A GRAPH LIKE THIS…
HIGH ENERGY
LOW ENERGY
CELERY
YOGURTCELERY
CANDY
ICE CREAM
WATER
PASTA
ENERGY CHANGES IN REACTIONS
REACTIONS USUALLY INCLUDE A CHANGE IN THE ENERGY OF THE “SYSTEM”
IE. The potential energy of the reactants is NOT the same as the potential energy of the products
IE. CH4 + O2 → H2O + CO2 high energy → low energy
ENERGY CHANGES IN REACTIONS
REACTIONH
EA
T
ENDOTHERMICDEF: A REACTION THAT ABSORBS ENERGY
FACT: THE REACTION ABSORBS HEAT FROM THE SURROUNDINGS AND THEREFORE USUALLY FEELS COOLERIE. Evaporating water
HEAT HEAT
ENERGY CHANGES IN REACTIONS
THE POTENTIAL ENERGY DIAGRAM OF AN ENDOTHERMIC REACTION WOULD LOOK LIKE THIS:
REACTANTS(START OF RXN)
PRODUCTS(END OF RXN)
PROGRES
S
OF RXN
ENERGY CHANGES IN REACTIONS
REACTIONH
EA
T
EXOTHERMICDEF: A REACTION THAT RELEASES ENERGY
FACT: THE REACTION RELEASES HEAT TO THE SURROUNDINGS AND THEREFORE USUALLY FEELS WARMERIE. Burning a fuel
HEAT HEAT
ENERGY CHANGES IN REACTIONS
THE POTENTIAL ENERGY DIAGRAM OF AN EXOTHERMIC REACTION WOULD LOOK LIKE THIS:
REACTANTS(START OF RXN)
PRODUCTS(END OF RXN)
PROGRESS
OF RXN
ENERGY CHANGES IN REACTIONS
SOME RXNS REQUIRE ENERGY TO BE ADDED TO START THE RXN…
BUT AFTER IT STARTS YOU DON’T HAVE TO KEEP ADDING ENERGY.ACTIVATION ENERGYDEF: THE ENERGY REQUIRED TO START A REACTIONIE. Lighting a match
ENERGY CHANGES IN REACTIONS
THE POTENTIAL ENERGY DIAGRAM OF AN EXOTHERMIC REACTION WITH AN ACTIVATION ENERGY WOULD LOOK LIKE THIS:
PRODUCTS(END OF RXN)
PROGRESS OF
RXN
ACT.
ENER
GY
ACTIVATED
REACTANTS(START OF RXN)
