Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

1. Matter and Measurements

Physical & Chemical Changes

GOB Chemistry

1. Matter and Measurements

Physical & Chemical Changes

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1:30 minutes

Problem 38

Textbook Question

Name two changes of state and describe what causes each to occur.

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Identify the first change of state: Melting. Melting occurs when a solid changes into a liquid. This happens when the solid absorbs heat energy, causing the particles to vibrate more vigorously until they overcome the forces holding them in a fixed position. The temperature at which this occurs is called the melting point.

Identify the second change of state: Condensation. Condensation occurs when a gas changes into a liquid. This happens when the gas loses heat energy, causing the particles to slow down and come closer together, forming intermolecular attractions. This typically occurs at the dew point or when the gas comes into contact with a cooler surface.

Explain the role of energy in these changes: In melting, energy is absorbed by the substance, which increases the kinetic energy of the particles. In condensation, energy is released by the substance, which decreases the kinetic energy of the particles.

Discuss the importance of temperature: For melting, the temperature must reach the melting point of the substance. For condensation, the temperature must drop to or below the dew point for the gas to transition into a liquid.

Summarize the processes: Melting is an endothermic process (absorbs heat), while condensation is an exothermic process (releases heat). Both involve changes in the energy and arrangement of particles, leading to a change in the state of matter.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Melting

Melting is the process where a solid turns into a liquid when it absorbs heat. This occurs because the added thermal energy increases the kinetic energy of the particles in the solid, causing them to vibrate more vigorously until they overcome the forces holding them in a fixed position, resulting in a liquid state.

Condensation

Condensation is the change of state from a gas to a liquid, typically occurring when the gas cools down. As the temperature drops, the kinetic energy of the gas particles decreases, allowing intermolecular forces to pull the particles closer together, forming liquid droplets, as seen in dew formation on grass.

Evaporation

Evaporation is the process by which a liquid turns into a gas, occurring at the surface of the liquid when molecules gain enough energy to break free from the liquid's surface. This can happen at any temperature, but is accelerated by factors such as increased temperature, surface area, and decreased atmospheric pressure.

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