1.†††††††† Energy is the capacity to do work.

 

2.†††††††† ultraviolet light; visible light

 

3.†††††††† From page 5 #3, Ek = 0.5mv2 = 0.005(1000)2 = 2500 J. With sig figs= 3 X 103 J

 

4.†††††††† Potential energy is energy that is due to position or composition. Kinetic energy is energy due to movement. At the top of a roller coaster, when the cart is not moving, its energy is strictly potential. At the bottom all of the energy of the moving cart is kinetic. Since molecules are always moving and since they have bonds, they always have both types of energy, but one form can be converted into another. For example, during an explosion a lot of potential energy is converted into kinetic energy during the sudden increase in pressure.

 

5.†††††††† (1)††††††† Water on top of a hill (potential energy due to position)

††††††††††† (2)††††††† The potential energy stored inside a sugar molecule.

††††††††††† (3)††††††† Potential energy as a result of H bonding

 

6.†††††††† Conservation of mass.

 

7.†††††††† a.†††††††† electricity

††††††††††† b.†††††††† heat and mechanical energy

 

8.†††††††† a.†††††††† rotation, vibration and translation

††††††††††† b.†††††††† they gain kinetic energy as they move faster

††††††††††† c.†††††††† they lose kinetic energy as they move slower

 

9.†††††††† a.†††††††† They have potential energy because of bonds.

††††††††††† b.†††††††† Intermolecular bonds exist between molecules.

††††††††††††††††††††††† Intramolecular bonds exist within molecules (between its atoms)

 

10.†††††† It either increases or decreases/

 

11.†††††† Enthalpy is the total heat content of molecules or the sum of potential and kinetic energies of molecules.

 

12.†††††† An endothermic reactions steals heat from its environment; an exothermic reaction releases heat.

 

13.†††††† For operations that have only subtraction and addition, we donít count the number of sig figs. For more details, see p7 of lab manual.

H of reactants (kJ)

H of products (kJ)

Enthalpy Change, DH (kJ)

Exo or Endo?

44

73

29

endo

288

88

-200

exo

44

41

-3

exo

555

500

-55

exo

222

444

222

endo

33

288

255

endo

310

222

-88

exo

17

55

38

endo

 

14.†††††† see profiles in notes

 

15.†††††† NH4Cl††††††††††††† endo ( temperature decreased)

††††††††††† NaOH††††††††††††† exo

††††††††††† NaCl††††††††††††††† neither ( in reality, it's just slightly endothermic)

††††††††††† Drano†††††††††††††† mucho exo

 

16.†††††† (1)††††††† exo

††††††††††† (2)††††††† exo

††††††††††† (3)††††††† endo

††††††††††† (4)††††††† endo

††††††††††† (5)††††††† exo

 

17.†††††† 1.†††††††† none of the above

††††††††††† 2.†††††††† c

††††††††††† 3.†††††††† b

††††††††††† 4.†††††††† a

††††††††††† 5.†††††††† d

 

18.†††††† a, d, f