ENERGY CHANGES IN REACTIONS

1. ENERGY CHANGES IN REACTIONS

2. HEAT DEFINITION: • ENERGY • THE ABILITY TO DO WORK

3. 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 INFRARED < RED < PURPLE < ULTRAVIOLET

4. TYPES OF ENERGY KINETIC ENERGY: • DEF: ENERGY BECAUSE OF MOTION THIS 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)

5. 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.)

6. POTENTIAL ENERGY • POTENTIAL ENERGY IS FREQUENTLY SHOWN ON A GRAPH LIKE THIS… HIGH ENERGY LOW ENERGY ICE CREAM CANDY PASTA YOGURT CELERY CELERY WATER

7. 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

8. ENERGY CHANGES IN REACTIONS • ENDOTHERMIC DEF: A REACTION THAT ABSORBS ENERGY FACT: THE REACTION ABSORBS HEAT FROM THE SURROUNDINGS AND THEREFORE USUALLY FEELS COOLER IE. Evaporating water REACTION HEAT HEAT HEAT

9. ENERGY CHANGES IN REACTIONS • THE POTENTIAL ENERGY DIAGRAM OF AN ENDOTHERMIC REACTION WOULD LOOK LIKE THIS: PRODUCTS (END OF RXN) PROGRESS OF RXN REACTANTS (START OF RXN)

10. ENERGY CHANGES IN REACTIONS • EXOTHERMIC DEF: A REACTION THAT RELEASES ENERGY FACT: THE REACTION RELEASES HEAT TO THE SURROUNDINGS AND THEREFORE USUALLY FEELS WARMER IE. Burning a fuel REACTION HEAT HEAT HEAT

11. ENERGY CHANGES IN REACTIONS • THE POTENTIAL ENERGY DIAGRAM OF AN EXOTHERMIC REACTION WOULD LOOK LIKE THIS: REACTANTS (START OF RXN) PROGRESS OF RXN PRODUCTS (END OF RXN)

12. 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 ENERGY DEF: THE ENERGY REQUIRED TO START A REACTION IE. Lighting a match

13. ENERGY CHANGES IN REACTIONS • THE POTENTIAL ENERGY DIAGRAM OF AN EXOTHERMIC REACTION WITH AN ACTIVATION ENERGY WOULD LOOK LIKE THIS: ACTIVATED ACT. ENERGY PROGRESS OF RXN REACTANTS (START OF RXN) PRODUCTS (END OF RXN)