Energy in Chemical Reactions

Chapter 20

I.         Heat

            A.        Energy transfer that changes temperature

            B.        

            C.        Energy may be stored in bonds or released from bonds

                        1.         

                        2.          Must add 572J

            D.        Law of Conservation of Energy

II.        Exothermic Reactions

            A.        Energy released to environment

                        1.         Heat

                        2.         Light

                        3.         Sound

            B.        Temperature increases

            C.        Fig 20.1 in text           

III.       Endothermic Reactions

            A.        Energy absorbed from environment

            B.        Temperature decreases

            C.        Figure 20.1 in text

IV.      Activation Energy

            A.        Energy needed to start a reaction

            B.        Most continue with no need for extra energy

            C.        Increased KE increases motion which increases collisions

            D.        Fig 20.4 in text

            E.        Catalyst lowers activation energy

V.        What drives reactions: Energy Level

            A.        Lower energy more stable

            B.        Chemicals naturally go from high to low

            C.        Reaction goes in direction to lower energy of chemicals

VI.      What drives reactions: Entropy

            A.        A measure of disorder

            B.        Natural systems move to increase

            C.        Not conserved

VII.     What Impacts Entropy

            A.        Number of molecules

            B.        Distribution of energy

            C.        Velocities

            D.        Positions

            E.        States of Matter

VIII.    Example 1

            A.        Entropy: more molecules

            B.        Energy: exothermic

IX.      Example 2

            A.        Entropy: more disordered states

            B.        Energy: exothermic

X.        Example 3 (nitroglycerine)

            A.        Entropy: ??????

            B.        Energy: ??????

            C.        Spontaneous: ????????

XI.      Calorimetry

            A.        Measures temperature change

            B.        Calculate energy change

            C.        

                        1.         Q: energy/heat

                        2.         m: mass

                        3.         T: temperature

                        4.         C: specific heat (unique to material)

            D.        Measure products and reactants mass

            E.        Measure temperature change

            F.        Look up C

XII.     Energy in Food

            A.        Kilocalories

                        1.         Energy needed to raise 1kg 1ºC

                        2.         Equal to 4.184J

            B.        Food in kcal (C)

            C.        Found by combustion

            D.        Energy release same as combustion but slow

XIII.    Economic Issues

            A.        Recycling

                        1.         Mining

                        2.         Refining

                        3.         Manufacturing

                        4.         ex. Al

            B.        Electricity

                        1.         Convert chemical to KE

                        2.         Convert KE to electrical

            C.        Entropy

                        1.         Waste heat

                        2.         Randomness

XIV.   Photosynthesis

            A.        Overall:

            B.        Light Reactions

            C.        Dark Reactions (Calvin Cycle)

XV.     Light Reactions

            A.        Light energizes chlorophyll, high energy e^- released

            B.        e^- gives energy to ADP and joins another chlorophyll

            C.        ADP forms ATP for Calvin cycle

            D.        Light energizes chlorophyll, high energy e^- released

            E.        e^- gives energy to NADP⁺ and H⁺

            F.        NADP⁺, H⁺, and e^- form NADPH for Calvin Cycle

            G.        H₂O decomposes to form H⁺, O₂, and e^-

            H.        e^- to chlorophyll, H⁺ to NADP, O₂ waste

XVI.   Dark Reactions

            A.        CO₂ plus H₂O plus C₅ form two C₃'s

            B.        ATP and NADPH convert C₃'s to PGAL

            C.        ATP converts PGAL to C₅

            D.        Every 6 cycles 1 glucose output

XVII.  Decrease in Entropy ??

            A.        Lower in organism

            B.        Higher in environment

            C.        Overall increase