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 the Phase Change Worksheet step by step, using the provided graph and information.
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The graph shows temperature vs. time for a substance being heated at a constant rate. The horizontal (flat) segments indicate phase changes, where temperature remains constant as energy is used to change the state of matter.
Key features:
- A → B: Solid heating up.
- B → C: Melting (solid → liquid), temperature constant at ~70°C.
- C → D: Liquid heating up.
- D → E: Boiling (liquid → gas), temperature constant at ~140°C.
- E onward: Gas heating up.
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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/thermal 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.
✔ Explanation: In solids, particles are tightly packed with fixed positions, so they have definite shape and volume. Adding heat increases kinetic energy → faster vibrations → temperature rises.
> At point B, the temperature of the substance is 70°C. The solid begins to melt.
✔ From the graph: Temperature levels off at 70°C from ~5 to 9 minutes → melting point = 70°C.
> At point C, the substance is completely melted or in a liquid state. Material in this phase has definite volume and no definite shape.
✔ Liquids take the shape of their container but maintain volume.
> The energy put to the substance between minutes 5 and 9 was used to convert the substance from a solid to a liquid.
✔ This is the melting phase (B → C), where temperature is constant but energy is absorbed to break intermolecular bonds.
> Between 9 and 13 minutes, the added energy increases the temperature of the substance.
✔ After melting is complete (at point C), the liquid heats up → temperature rises again.
> During the time from point D to point E, the liquid is boiling.
✔ Flat line from 13 to 18 minutes at 140°C → boiling point reached.
> By point E, the substance is completely in the gas phase.
✔ After boiling finishes at E, only gas remains.
> Material in this phase has no definite volume and no definite shape.
✔ Gases expand to fill container — no fixed shape or volume.
> The energy put to the substance between minutes 13 and 18 converted the substance from a liquid to a gas state.
✔ This is the vaporization (boiling) phase.
> Beyond point E, the substance is still in the gas phase, but the molecules are moving faster as indicated by the increasing temperature.
✔ Temperature increases → increased kinetic energy → faster molecular motion.
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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/thermal 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 melted or in a liquid state. Material in this phase has definite volume and no definite 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 no definite volume and no definite 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 compare the melting point and boiling point observed on the graph:
- Melting point: 70°C (from B to C)
- Boiling point: 140°C (from D to E)
Now check the table:
| Substance | Melting Point | Boiling Point |
|---------------|----------------|----------------|
| Bolognium | 20°C | 100°C |
| Unobtainium | 40°C | 140°C |
| Foosium | 70°C | 140°C |
Only Foosium matches both:
- Melting point: 70°C
- Boiling point: 140°C
✔ So, the substance used is Foosium.
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Foosium
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- Melting point: 70°C → matches Foosium
- Boiling point: 140°C → matches Foosium
- Phase changes:
- Solid → liquid at 70°C
- Liquid → gas at 140°C
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23. Foosium was likely used in this phase change experiment.
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Understanding the Graph
The graph shows temperature vs. time for a substance being heated at a constant rate. The horizontal (flat) segments indicate phase changes, where temperature remains constant as energy is used to change the state of matter.
Key features:
- A → B: Solid heating up.
- B → C: Melting (solid → liquid), temperature constant at ~70°C.
- C → D: Liquid heating up.
- D → E: Boiling (liquid → gas), temperature constant at ~140°C.
- E onward: Gas heating up.
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Answering 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/thermal 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.
✔ Explanation: In solids, particles are tightly packed with fixed positions, so they have definite shape and volume. Adding heat increases kinetic energy → faster vibrations → temperature rises.
> At point B, the temperature of the substance is 70°C. The solid begins to melt.
✔ From the graph: Temperature levels off at 70°C from ~5 to 9 minutes → melting point = 70°C.
> At point C, the substance is completely melted or in a liquid state. Material in this phase has definite volume and no definite shape.
✔ Liquids take the shape of their container but maintain volume.
> The energy put to the substance between minutes 5 and 9 was used to convert the substance from a solid to a liquid.
✔ This is the melting phase (B → C), where temperature is constant but energy is absorbed to break intermolecular bonds.
> Between 9 and 13 minutes, the added energy increases the temperature of the substance.
✔ After melting is complete (at point C), the liquid heats up → temperature rises again.
> During the time from point D to point E, the liquid is boiling.
✔ Flat line from 13 to 18 minutes at 140°C → boiling point reached.
> By point E, the substance is completely in the gas phase.
✔ After boiling finishes at E, only gas remains.
> Material in this phase has no definite volume and no definite shape.
✔ Gases expand to fill container — no fixed shape or volume.
> The energy put to the substance between minutes 13 and 18 converted the substance from a liquid to a gas state.
✔ This is the vaporization (boiling) phase.
> Beyond point E, the substance is still in the gas phase, but the molecules are moving faster as indicated by the increasing temperature.
✔ Temperature increases → increased kinetic energy → faster molecular motion.
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✔ Final Answers (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/thermal 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 melted or in a liquid state. Material in this phase has definite volume and no definite 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 no definite volume and no definite 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 compare the melting point and boiling point observed on the graph:
- Melting point: 70°C (from B to C)
- Boiling point: 140°C (from D to E)
Now check the table:
| Substance | Melting Point | Boiling Point |
|---------------|----------------|----------------|
| Bolognium | 20°C | 100°C |
| Unobtainium | 40°C | 140°C |
| Foosium | 70°C | 140°C |
Only Foosium matches both:
- Melting point: 70°C
- Boiling point: 140°C
✔ So, the substance used is Foosium.
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✔ Final Answer to Question 23:
Foosium
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🟩 Summary
- Melting point: 70°C → matches Foosium
- Boiling point: 140°C → matches Foosium
- Phase changes:
- Solid → liquid at 70°C
- Liquid → gas at 140°C
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✔ Final Answer:
23. Foosium was likely used in this phase change experiment.
Parent Tip: Review the logic above to help your child master the concept of phase change worksheet with answers.
