1. Energy in Chemical Reactions

2. What is Energy? The ability to do work or produce heat.
Potential Energy – stored energy.
Kinetic Energy – energy of motion.

3. What is Enthalpy (∆H)?
The quantity that measures changes in energy in systems.
It has the same of units as energy (kilojoules, joules, calories)

4. System – the participating members of a reaction or change.
Surroundings – everything outside the system. This is where we measure energy changes. Whether the surroundings gain or lose energy.

5. Endothermic – heat energy absorbed
Exothermic – heat energy given off

6. What is a Calorimeter?
An insulated device that measures heat changes in a chemical reaction.

7. Heat: the total amount of energy transferred
Heat: the total amount of energy transferred. Heat transfers from hot to cold. Cold is the absence of heat, or energy.
What is Temperature?: average kinetic energy (random motion) of all the particles in a system. The faster they move, the hotter they are.

8. Specific Heat Capacity (c) or (cp)
Measure how well a substance absorbs or loses heat. The amount of heat energy it takes to raise the temperature of 1 gram of a substance, 1˚C.
UNITS: Units in (J/g˚C) or (cal/g˚C)
Low specific heat capacity – temperature changes easily, ex: metals
High specific heat capacity – temp. changes slowly, substance retains its heat energy and will absorb it slowly. Ex: water

9. Chemical Reactions are occurring everywhere
Chemical Reactions are occurring everywhere. From the ignition of your car, to the burning of fuel, and the rusting of the gas tank, interacting particles will always combine, break apart, and reorganize in order to achieve lower energy & stability

10. Reaction Diagram
Products
Potential
Energy
Reactants
Reaction

11. Activation Energy (Ea) - the minimum energy necessary to start a chemical reaction. This energy comes from the surroundings Ea
Potential
Energy
Reaction

12. ∆H is the Change in Enthalpy ∆H = Energy of Products – Energy of Reactants
Potential
Energy ∆H
Reaction

13. Within the “system”
Exothermic Reactions: energy is given off from the reaction. This will result in a negative enthalpy (-ΔH). E N R G Y Ea
-ΔH
Reaction

14. Within the “system”
Endothermic Reactions: energy is absorbed from the reaction. This will result in a positive enthalpy (+ΔH). E N R G Y Ea
+ΔH
Reaction

15. What is a catalyst?
A catalyst is a substance which increases the rate of a reaction without being consumed itself.
Effect of a Catalyst: a catalyst will lower the activation energy of a reaction. This will speed up the rate of the reaction.

16. Reaction Diagram WS!

17. Pg. 581 #6