Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

8. Thermochemistry

Endothermic & Exothermic Reactions

General Chemistry

8. Thermochemistry

Endothermic & Exothermic Reactions

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Multiple Choice

Which of the following exchanges of energy has a positive sign for heat (relative to the system)?

snow melts on a mountaintop (snow is the system)

water vapor condenses on a cold surface (water vapor is the system)

a rock tumbles from a mountain (the rock is the system)

both the first and second choices

both the first and third choices

both the second and third choices

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Verified step by step guidance

Understand the concept of heat exchange: In thermodynamics, heat exchange refers to the transfer of thermal energy between a system and its surroundings. A positive sign for heat indicates that the system is absorbing heat from the surroundings.

Analyze the first scenario: 'snow melts on a mountaintop (snow is the system)'. Melting is an endothermic process, meaning the system (snow) absorbs heat from the surroundings to change from solid to liquid.

Analyze the second scenario: 'water vapor condenses on a cold surface (water vapor is the system)'. Condensation is an exothermic process, meaning the system (water vapor) releases heat to the surroundings to change from gas to liquid.

Analyze the third scenario: 'a rock tumbles from a mountain (the rock is the system)'. This scenario involves mechanical energy rather than thermal energy, and typically does not involve heat exchange in the context of thermodynamics.

Determine which scenarios involve a positive sign for heat: Based on the analysis, the first scenario (snow melting) involves a positive sign for heat as the system absorbs heat. The second scenario involves a negative sign for heat as the system releases heat. The third scenario does not involve heat exchange.