Endothermic and Exothermic Processes - AP Chemistry

1. Identify an endothermic process in everyday life.

   Photosynthesis is an endothermic process. Light energy is absorbed to drive the reaction.

2. Identify whether the evaporation of alcohol is endothermic or exothermic.

   Evaporation of alcohol is endothermic. Phase change requires energy input.

3. Identify whether freezing water is endothermic or exothermic.

   Freezing water is an exothermic process. Energy is released as molecules form ordered structure.

4. State the relationship between $\triangle H$ and reaction spontaneity.

   $\triangle H$ alone does not determine spontaneity. Gibbs free energy determines spontaneity.

5. State the unit commonly used for enthalpy change.

   The unit is kilojoules per mole (kJ/mol). Standard unit for measuring enthalpy changes.

6. What is the heat of reaction?

   The heat absorbed or released during a chemical reaction. Energy change when reactants become products.

7. What does a positive $\triangle H$ indicate about heat flow?

   Heat is absorbed by the system. System gains energy from surroundings.

8. What is a non-spontaneous process?

   A process that requires continuous external energy input. Thermodynamically unfavorable without energy input.

9. Identify the sign of $\triangle H$ for exothermic reactions.

   $\triangle H$ is negative for exothermic reactions. Energy is released, so enthalpy decreases.

10. Identify whether lighting a match is endothermic or exothermic.

    Lighting a match is exothermic. Combustion of match head releases energy.

11. What does a negative $\triangle H$ indicate about heat flow?

    Heat is released by the system. System loses energy to surroundings.

12. What is the standard state condition for enthalpy changes?

    1 atm pressure and 298 K temperature. Reference conditions for thermodynamic measurements.

13. State the First Law of Thermodynamics.

    Energy cannot be created or destroyed, only transformed. Conservation of energy principle in thermodynamics.

14. What does a positive $\triangle H$ indicate about heat flow?

    Heat is absorbed by the system. System gains energy from surroundings.

15. What is the standard state condition for enthalpy changes?

    1 atm pressure and 298 K temperature. Reference conditions for thermodynamic measurements.

16. Which phase change is endothermic: melting or freezing?

    Melting is endothermic. Energy is needed to break intermolecular forces.

17. Identify whether the rusting of iron is endothermic or exothermic.

    Rusting of iron is exothermic. Oxidation reactions release energy.

18. Differentiate between system and surroundings in thermodynamics.

    The system is the part of the universe being studied; surroundings are everything else. Defines boundaries for energy transfer analysis.

19. Identify an exothermic process in everyday life.

    Burning wood is an exothermic process. Combustion releases energy as heat and light.

20. Identify the sign of $\triangle H$ for endothermic reactions.

    $\triangle H$ is positive for endothermic reactions. Energy is absorbed, so enthalpy increases.

21. Differentiate between system and surroundings in thermodynamics.

    The system is the part of the universe being studied; surroundings are everything else. Defines boundaries for energy transfer analysis.

22. What is the sign of $\triangle H$ for a reaction that absorbs heat?

    The sign of $\triangle H$ is positive. Heat absorption means positive enthalpy change.

23. What is a non-spontaneous process?

    A process that requires continuous external energy input. Thermodynamically unfavorable without energy input.

24. Is dissolving ammonium nitrate in water endothermic or exothermic?

    It is an endothermic process. Dissolution breaks ionic bonds, absorbing energy.

25. Identify whether freezing water is endothermic or exothermic.

    Freezing water is an exothermic process. Energy is released as molecules form ordered structure.

26. Identify an exothermic process in everyday life.

    Burning wood is an exothermic process. Combustion releases energy as heat and light.

27. What is meant by a spontaneous process?

    A process that occurs without external energy input. Thermodynamically favorable under given conditions.

28. Which type of reaction is combustion?

    Combustion is an exothermic reaction. Burning reactions always release energy.

29. Calculate $\triangle H$: Reactants = 100 kJ, Products = 180 kJ.

    $\triangle H = 180 - 100 = 80$ kJ. Products have higher energy than reactants.

30. Identify an exothermic process in everyday life.

    Burning wood is an exothermic process. Combustion releases energy as heat and light.

31. What is a non-spontaneous process?

    A process that requires continuous external energy input. Thermodynamically unfavorable without energy input.

32. Identify whether baking bread is endothermic or exothermic.

    Baking bread is an endothermic process. Chemical reactions in baking require energy input.

33. State the First Law of Thermodynamics.

    Energy cannot be created or destroyed, only transformed. Conservation of energy principle in thermodynamics.

34. What is an exothermic process?

    A process that releases heat to its surroundings. Heat flows out of the system to the environment.

35. What does a calorimeter measure?

    A calorimeter measures the heat of chemical reactions. Device that quantifies energy changes in reactions.

36. What is the sign of $\triangle H$ for a reaction that releases heat?

    The sign of $\triangle H$ is negative. Heat release means negative enthalpy change.

37. Which type of reaction is combustion?

    Combustion is an exothermic reaction. Burning reactions always release energy.

38. Identify whether the rusting of iron is endothermic or exothermic.

    Rusting of iron is exothermic. Oxidation reactions release energy.

39. Calculate $\triangle H$: Reactants = 200 kJ, Products = 150 kJ.

    $\triangle H = 150 - 200 = -50$ kJ. Products have lower energy than reactants.

40. Identify whether freezing water is endothermic or exothermic.

    Freezing water is an exothermic process. Energy is released as molecules form ordered structure.

41. Which type of reaction is combustion?

    Combustion is an exothermic reaction. Burning reactions always release energy.

42. What does a calorimeter measure?

    A calorimeter measures the heat of chemical reactions. Device that quantifies energy changes in reactions.

43. What is meant by a spontaneous process?

    A process that occurs without external energy input. Thermodynamically favorable under given conditions.

44. What is the sign of $\triangle H$ for a reaction that releases heat?

    The sign of $\triangle H$ is negative. Heat release means negative enthalpy change.

45. What is the standard state condition for enthalpy changes?

    1 atm pressure and 298 K temperature. Reference conditions for thermodynamic measurements.

46. Identify whether lighting a match is endothermic or exothermic.

    Lighting a match is exothermic. Combustion of match head releases energy.

47. Calculate $\triangle H$: Reactants = 100 kJ, Products = 180 kJ.

    $\triangle H = 180 - 100 = 80$ kJ. Products have higher energy than reactants.

48. Identify whether the rusting of iron is endothermic or exothermic.

    Rusting of iron is exothermic. Oxidation reactions release energy.

49. State the enthalpy change for an exothermic reaction.

    $\triangle H$ is negative. Energy is released during the reaction.

50. Identify if dissolving NaCl in water is endothermic or exothermic.

    Dissolving NaCl in water is endothermic. Ion separation requires energy input.

51. What does a calorimeter measure?

    A calorimeter measures the heat of chemical reactions. Device that quantifies energy changes in reactions.

52. Identify whether lighting a match is endothermic or exothermic.

    Lighting a match is exothermic. Combustion of match head releases energy.

53. State the enthalpy change for an exothermic reaction.

    $\triangle H$ is negative. Energy is released during the reaction.

54. Identify whether boiling water is endothermic or exothermic.

    Boiling water is an endothermic process. Energy is required to overcome intermolecular forces.

55. Which phase change is exothermic: condensation or vaporization?

    Condensation is exothermic. Energy is released when gas molecules organize.

56. State the enthalpy change for an endothermic reaction.

    $\triangle H$ is positive. Energy is absorbed during the reaction.

57. State the First Law of Thermodynamics.

    Energy cannot be created or destroyed, only transformed. Conservation of energy principle in thermodynamics.

58. Identify whether the evaporation of alcohol is endothermic or exothermic.

    Evaporation of alcohol is endothermic. Phase change requires energy input.

59. What is meant by activation energy?

    The minimum energy required to initiate a reaction. Energy barrier that must be overcome.

60. What is the heat of reaction?

    The heat absorbed or released during a chemical reaction. Energy change when reactants become products.

61. What is an endothermic process?

    A process that absorbs heat from its surroundings. Heat flows into the system from the environment.

62. What does a positive $\triangle H$ indicate about heat flow?

    Heat is absorbed by the system. System gains energy from surroundings.

63. Calculate $\triangle H$: Reactants = 100 kJ, Products = 180 kJ.

    $\triangle H = 180 - 100 = 80$ kJ. Products have higher energy than reactants.

64. State Hess's Law.

    The total enthalpy change is the same no matter how the reaction is carried out. Enthalpy is path-independent, only depends on states.

65. State the enthalpy change for an endothermic reaction.

    $\triangle H$ is positive. Energy is absorbed during the reaction.

66. State the enthalpy change for an exothermic reaction.

    $\triangle H$ is negative. Energy is released during the reaction.

67. What is the sign of $\triangle H$ for a reaction that absorbs heat?

    The sign of $\triangle H$ is positive. Heat absorption means positive enthalpy change.

68. What is meant by activation energy?

    The minimum energy required to initiate a reaction. Energy barrier that must be overcome.

69. Identify whether the evaporation of alcohol is endothermic or exothermic.

    Evaporation of alcohol is endothermic. Phase change requires energy input.

70. Identify whether boiling water is endothermic or exothermic.

    Boiling water is an endothermic process. Energy is required to overcome intermolecular forces.

71. Identify whether boiling water is endothermic or exothermic.

    Boiling water is an endothermic process. Energy is required to overcome intermolecular forces.

72. What is the heat of reaction?

    The heat absorbed or released during a chemical reaction. Energy change when reactants become products.

73. What does $\triangle H$ represent in thermochemistry?

    $\triangle H$ represents the change in enthalpy. It measures energy changes in chemical reactions.

74. State Hess's Law.

    The total enthalpy change is the same no matter how the reaction is carried out. Enthalpy is path-independent, only depends on states.

75. Define enthalpy ($H$) in thermodynamics.

    Enthalpy is the total heat content of a system. It's a state function measuring internal energy.

76. What is the sign of $\triangle H$ for a reaction that absorbs heat?

    The sign of $\triangle H$ is positive. Heat absorption means positive enthalpy change.

77. What is meant by activation energy?

    The minimum energy required to initiate a reaction. Energy barrier that must be overcome.

78. Which phase change is exothermic: condensation or vaporization?

    Condensation is exothermic. Energy is released when gas molecules organize.

79. Differentiate between system and surroundings in thermodynamics.

    The system is the part of the universe being studied; surroundings are everything else. Defines boundaries for energy transfer analysis.

80. What is the heat of formation?

    The change in enthalpy when one mole of a compound is formed. Standard enthalpy for compound synthesis from elements.

81. What is meant by a spontaneous process?

    A process that occurs without external energy input. Thermodynamically favorable under given conditions.

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