Phase Change Worksheet | Exercises Chemistry | Docsity - Free Printable
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Show Answer Key & Explanations
Step-by-step solution for: Phase Change Worksheet | Exercises Chemistry | Docsity
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Show Answer Key & Explanations
Step-by-step solution for: Phase Change Worksheet | Exercises Chemistry | Docsity
Let’s solve this step-by-step using the Phase Change Diagram provided.
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This is a heating curve — temperature vs. time — for a substance being heated at a constant rate.
Key features:
- Sloped lines: Temperature is rising → substance is in one phase (solid, liquid, or gas), absorbing heat to increase kinetic energy.
- Flat plateaus (horizontal lines): Phase change occurring → temperature stays constant while energy is used to break intermolecular forces (melting or boiling).
From the graph:
- AB segment: Solid heating up
- BC plateau: Melting (solid → liquid)
- CD segment: Liquid heating up
- DE plateau: Boiling (liquid → gas)
- Beyond E: Gas heating up
Now let’s fill in the blanks from Question 1–22:
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> At point A, the beginning of observations, the substance exists in a solid state. Material in this phase has definite volume and definite shape. With each passing minute, heat/energy is added to the substance. This causes the molecules of the substance to vibrate more rapidly which we detect by a temperature rise in the substance.
> At point B, the temperature of the substance is 70 °C. The solid begins to melt.
> At point C, the substance is completely liquid or in a liquid state. Material in this phase has definite volume and indefinite shape.
> The energy put to the substance between minutes 5 and 9 was used to convert the substance from a solid to a liquid.
> Between 9 and 13 minutes, the added energy increases the temperature of the substance.
> During the time from point D to point E, the liquid is boiling.
> By point E, the substance is completely in the gas phase. Material in this phase has indefinite volume and indefinite shape.
> The energy put to the substance between minutes 13 and 18 converted the substance from a liquid to a gas state.
> Beyond point E, the substance is still in the gas phase, but the molecules are moving faster as indicated by the increasing temperature.
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We need to match the melting point and boiling point from the graph to the table.
From the graph:
- Melting point = temperature during BC plateau → 70°C
- Boiling point = temperature during DE plateau → 140°C
Check the table:
| Substance | Melting point | Boiling point |
|---------------|---------------|---------------|
| Bolognium | 20°C | 100°C |
| Unobtainium | 40°C | 140°C |
| Foosium | 70°C | 140°C |
✔ Foosium matches both melting point (70°C) and boiling point (140°C).
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23. Foosium
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- Solid: definite shape & volume; molecules vibrate in place.
- Melting: occurs at melting point; temperature constant until all solid becomes liquid.
- Liquid: definite volume, indefinite shape; molecules slide past each other.
- Boiling: occurs at boiling point; temperature constant until all liquid becomes gas.
- Gas: indefinite volume & shape; molecules move freely and rapidly.
- Energy added during phase changes breaks bonds (not increases temp).
- Energy added during sloped segments increases molecular motion → increases temperature.
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✔ You’re all set! Let me know if you’d like a diagram explanation or printable version.
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🔍 Understanding the Graph:
This is a heating curve — temperature vs. time — for a substance being heated at a constant rate.
Key features:
- Sloped lines: Temperature is rising → substance is in one phase (solid, liquid, or gas), absorbing heat to increase kinetic energy.
- Flat plateaus (horizontal lines): Phase change occurring → temperature stays constant while energy is used to break intermolecular forces (melting or boiling).
From the graph:
- AB segment: Solid heating up
- BC plateau: Melting (solid → liquid)
- CD segment: Liquid heating up
- DE plateau: Boiling (liquid → gas)
- Beyond E: Gas heating up
Now let’s fill in the blanks from Question 1–22:
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✔ Answers to Questions 1–22:
> At point A, the beginning of observations, the substance exists in a solid state. Material in this phase has definite volume and definite shape. With each passing minute, heat/energy is added to the substance. This causes the molecules of the substance to vibrate more rapidly which we detect by a temperature rise in the substance.
> At point B, the temperature of the substance is 70 °C. The solid begins to melt.
> At point C, the substance is completely liquid or in a liquid state. Material in this phase has definite volume and indefinite shape.
> The energy put to the substance between minutes 5 and 9 was used to convert the substance from a solid to a liquid.
> Between 9 and 13 minutes, the added energy increases the temperature of the substance.
> During the time from point D to point E, the liquid is boiling.
> By point E, the substance is completely in the gas phase. Material in this phase has indefinite volume and indefinite shape.
> The energy put to the substance between minutes 13 and 18 converted the substance from a liquid to a gas state.
> Beyond point E, the substance is still in the gas phase, but the molecules are moving faster as indicated by the increasing temperature.
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🧪 Question 23: Which substance was likely used?
We need to match the melting point and boiling point from the graph to the table.
From the graph:
- Melting point = temperature during BC plateau → 70°C
- Boiling point = temperature during DE plateau → 140°C
Check the table:
| Substance | Melting point | Boiling point |
|---------------|---------------|---------------|
| Bolognium | 20°C | 100°C |
| Unobtainium | 40°C | 140°C |
| Foosium | 70°C | 140°C |
✔ Foosium matches both melting point (70°C) and boiling point (140°C).
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✔ Final Answer:
23. Foosium
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📝 Summary of Key Concepts:
- Solid: definite shape & volume; molecules vibrate in place.
- Melting: occurs at melting point; temperature constant until all solid becomes liquid.
- Liquid: definite volume, indefinite shape; molecules slide past each other.
- Boiling: occurs at boiling point; temperature constant until all liquid becomes gas.
- Gas: indefinite volume & shape; molecules move freely and rapidly.
- Energy added during phase changes breaks bonds (not increases temp).
- Energy added during sloped segments increases molecular motion → increases temperature.
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✔ You’re all set! Let me know if you’d like a diagram explanation or printable version.
Parent Tip: Review the logic above to help your child master the concept of phase change graph worksheet.
