Educational worksheet on phase changes and states of matter with a diagram and multiple-choice questions.

Problem Analysis:

The image provided is a diagram showing the phase changes of matter as it is heated or cooled. The diagram includes three states of matter: solid, liquid, and gas, along with two line segments labeled A and B. These line segments represent transitions between phases.

- Line Segment A: Transition from solid to liquid (melting).
- Line Segment B: Transition from liquid to gas (vaporization).

The questions in the image are related to these phase changes and their associated thermal energy changes. Let's solve each question step by step.

---

Question 11: What is happening to the temperature and thermal energy at Line Segments A and B?

#### Solution:
- Line Segment A (Solid to Liquid):
- Temperature: Remains constant during this phase change because the added thermal energy is used to break intermolecular bonds, not to increase kinetic energy.
- Thermal Energy: Increases as heat is absorbed to melt the solid into a liquid.

- Line Segment B (Liquid to Gas):
- Temperature: Remains constant during this phase change because the added thermal energy is used to overcome intermolecular forces, not to increase kinetic energy.
- Thermal Energy: Increases as heat is absorbed to vaporize the liquid into a gas.

#### Answer:
At both Line Segments A and B, the temperature remains constant, but the thermal energy increases.

---

Question 12: If the substance is being heated toward Line A, a change of state is called...

#### Solution:
- Line A represents the transition from a solid to a liquid.
- The process of changing from a solid to a liquid is called melting.

#### Answer:
Melting

---

Question 13: If the substance is being cooled toward Line A, a change of state is called...

#### Solution:
- Line A represents the transition from a solid to a liquid.
- If the substance is being cooled toward Line A, it means it is transitioning from a liquid to a solid.
- The process of changing from a liquid to a solid is called freezing.

#### Answer:
Freezing

---

Question 14: If the substance is being heated toward Line B, a change of state is called...

#### Solution:
- Line B represents the transition from a liquid to a gas.
- The process of changing from a liquid to a gas is called vaporization.

#### Answer:
Vaporization

---

Question 15: If the substance is being cooled toward Line B, a change of state is called...

#### Solution:
- Line B represents the transition from a liquid to a gas.
- If the substance is being cooled toward Line B, it means it is transitioning from a gas to a liquid.
- The process of changing from a gas to a liquid is called condensation.

#### Answer:
Condensation

---

Question 16: If the thermal energy is decreasing, Line A could be called...

#### Solution:
- Line A represents the transition from a solid to a liquid when heated.
- When thermal energy is decreasing, the reverse process occurs: the liquid turns into a solid.
- This reverse process is called freezing.

#### Answer:
Freezing

---

Question 17: If the thermal energy is increasing, Line B could be called...

#### Solution:
- Line B represents the transition from a liquid to a gas when heated.
- When thermal energy is increasing, the liquid turns into a gas.
- This process is called vaporization.

#### Answer:
Vaporization

---

Multiple Choice Questions:

#### Question 18: Clouds, fog, and steam that you can see are all examples of which state of matter?
- Options: Solid, Liquid, Gas, Plasma

#### Solution:
- Clouds, fog, and steam are visible forms of water vapor, which is in the gas state.

#### Answer:
Gas

#### Question 19: An ice cube that gets smaller while resting on a table is an example of what?
- Options: Evaporation, Freezing, Condensation, Sublimation

#### Solution:
- An ice cube getting smaller indicates that it is turning directly from a solid (ice) into a gas (water vapor) without passing through the liquid state.
- This process is called sublimation.

#### Answer:
Sublimation

---

Final Answers:

1. Temperature remains constant; thermal energy increases.
2. Melting
3. Freezing
4. Vaporization
5. Condensation
6. Freezing
7. Vaporization
8. Gas
9. Sublimation

Boxed Final Answer:
\[
\boxed{\text{See detailed answers above.}}
\]