Phase Change Worksheet and KEY 1 - Phase Changes Worksheet Name ... - Free Printable

To solve the problem and explain the solution, let's analyze the given phase change diagram step by step. The diagram illustrates the changes in a substance as it transitions between different phases (solid, liquid, gas) with increasing heat energy.

Key Elements of the Diagram:

1. Horizontal Lines (Phase Changes):
- These represent phase changes where the temperature remains constant while heat is added.
- Each horizontal line corresponds to a specific phase change:
- A → B: Solid → Liquid (Melting)
- C → D: Liquid → Gas (Boiling/Vaporization)
- E → F: Solid → Gas (Sublimation)

2. Sloped Lines (Energy Absorption Without Phase Change):
- These represent the heating of the substance within a single phase (solid, liquid, or gas).
- Heat is absorbed, causing the temperature to increase.

3. Labels:
- A, B, C, D, E, F: Points on the graph representing specific states or transitions.
- Heat Energy: The x-axis represents the amount of heat energy added.
- Temperature: The y-axis represents the temperature of the substance.

Step-by-Step Analysis:

#### 1. Segment A → B:
- This segment represents the melting process (solid → liquid).
- During this phase, heat is added, but the temperature remains constant at the melting point.
- Explanation: The energy supplied during this phase is used to break intermolecular bonds, allowing the solid to transition into a liquid state without an increase in temperature.

#### 2. Segment B → C:
- This segment represents the heating of the liquid phase.
- As heat is added, the temperature of the liquid increases.
- Explanation: The energy supplied raises the kinetic energy of the liquid molecules, causing the temperature to rise.

#### 3. Segment C → D:
- This segment represents the boiling/vaporization process (liquid → gas).
- During this phase, heat is added, but the temperature remains constant at the boiling point.
- Explanation: The energy supplied during this phase is used to overcome the intermolecular forces, allowing the liquid to transition into a gaseous state without an increase in temperature.

#### 4. Segment D → E:
- This segment represents the heating of the gas phase.
- As heat is added, the temperature of the gas increases.
- Explanation: The energy supplied raises the kinetic energy of the gas molecules, causing the temperature to rise.

#### 5. Segment E → F:
- This segment represents the sublimation process (solid → gas).
- During this phase, heat is added, but the temperature remains constant.
- Explanation: The energy supplied during this phase is used to directly convert the solid into a gas without passing through the liquid phase.

Identifying Key Points:

- Point A: Starting point (solid phase at low temperature).
- Point B: End of melting (liquid phase at melting point temperature).
- Point C: Start of boiling (liquid phase at boiling point temperature).
- Point D: End of boiling (gas phase at boiling point temperature).
- Point E: Start of sublimation (solid phase at sublimation temperature).
- Point F: End of sublimation (gas phase after sublimation).

Solution Summary:

The phase change diagram shows the following transitions:
1. Solid → Liquid (Melting): Occurs at constant temperature (A → B).
2. Liquid → Gas (Boiling/Vaporization): Occurs at constant temperature (C → D).
3. Solid → Gas (Sublimation): Occurs at constant temperature (E → F).
4. Heating Within Phases: Temperature increases when heat is added without a phase change (B → C and D → E).

Final Answer:

The diagram illustrates the phase changes of a substance as it transitions from solid to liquid to gas, with distinct regions for melting, boiling, and sublimation. The key points are:
- Melting: A → B
- Boiling: C → D
- Sublimation: E → F

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\boxed{\text{The diagram shows the phase changes of a substance, including melting, boiling, and sublimation.}}
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