Heating Curves Worksheet 2 | PDF - Free Printable

Let's solve the Heating Curves Worksheet step by step, using the provided graph of the heating curve for Substance X.

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🔍 Understanding the Heating Curve

The graph shows temperature (°C) on the y-axis and time (minutes) on the x-axis. The substance is being heated at a constant rate.

There are five segments labeled I to V:

- I: Temperature increases from -15°C to 0°C → Solid warming
- II: Horizontal line at 0°C → Phase change: solid to liquid (melting)
- III: Temperature increases from 0°C to 55°C → Liquid warming
- IV: Horizontal line at 55°C → Phase change: liquid to vapor (boiling)
- V: Temperature increases above 55°C → Vapor warming

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✔ Now, answer each question:

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#### 1. In what part of the curve would substance X have a definite shape and definite volume?

👉 This describes the solid phase.

- The solid phase occurs in Segment I (before melting).
- During Segment I, the substance is solid and warming up.
- Answer: I

> ✔ Answer: I

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#### 2. In what part of the curve would substance X have a definite volume but no definite shape?

👉 This describes the liquid phase.

- The liquid has fixed volume but takes the shape of its container.
- This happens during Segment III, when it's fully liquid and warming.
- Answer: III

> ✔ Answer: III

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#### 3. In what part of the curve would substance X have no definite shape or volume?

👉 This describes the gas/vapor phase.

- Gases expand to fill their container — no definite shape or volume.
- This occurs in Segment V, after boiling.
- Answer: V

> ✔ Answer: V

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#### 4. What part of the curve represents a mixed solid/liquid phase of substance X?

👉 This is during melting, where both solid and liquid coexist.

- That happens during Segment II, where temperature is constant at 0°C.
- Answer: II

> ✔ Answer: II

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#### 5. What part of the curve represents a mixed liquid/vapor phase of substance X?

👉 This is during boiling, where liquid and vapor coexist.

- Happens during Segment IV, at 55°C.
- Answer: IV

> ✔ Answer: IV

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#### 6. What is the melting temperature of substance X?

👉 Melting occurs at the temperature plateau during Segment II.

- From the graph, this plateau is at 0°C.
- Answer: 0°C

> ✔ Answer: 0°C

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#### 7. What is the boiling temperature of substance X?

👉 Boiling occurs at the temperature plateau during Segment IV.

- This plateau is at 55°C.
- Answer: 55°C

> ✔ Answer: 55°C

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🔄 Circle the correct cooling curve for water

We are given three cooling curves. We need to pick the one that matches water.

Water:
- Freezes at 0°C
- Boils at 100°C
- Cooling curve should show:
- A horizontal plateau at 100°C (condensation: gas → liquid)
- Then cooling of liquid
- Then a horizontal plateau at 0°C (freezing: liquid → solid)
- Then cooling of solid

So the correct cooling curve must have:
- Two plateaus: one at 100°C, then one at 0°C
- The order: high temp → condense at 100°C → cool → freeze at 0°C → cool further

Now examine the options:

1. First graph: Plateau at 100°C → then drops to -100°C → no plateau at 0°C ✘
2. Second graph: Plateau at 100°C → drops → plateau at 0°C → drops further ✔
3. Third graph: Drops quickly → plateau at 0°C → drops → no plateau at 100°C ✘

✔ The second graph has two plateaus: at 100°C and at 0°C — matching water’s behavior.

> ✔ Correct answer: Second graph (middle one)

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✔ Final Answers:

1. I
2. III
3. V
4. II
5. IV
6. 0°C
7. 55°C

And circle the middle cooling curve (the one with plateaus at 100°C and 0°C).

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Let me know if you'd like a visual explanation or sketch!