Phase Change Worksheet | Exercises Chemistry | Docsity - Free Printable

Let’s work through this step by step.

We are given a Phase Change Diagram (temperature vs. time) and a table of three substances with their melting and boiling points.

The question (23) asks:
> Which of these three substances was likely used in this phase change experiment?

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Step 1: Understand what the graph shows

The graph plots Temperature (°C) on the y-axis and Time (minutes) on the x-axis.

There are flat parts (plateaus) where temperature doesn’t rise even though heat is being added — those are phase changes:

- First plateau: from about minute 5 to minute 9 → melting (solid to liquid)
- Second plateau: from about minute 14 to minute 18 → boiling (liquid to gas)

During plateaus, the substance is changing phase, so temperature stays constant at the melting point or boiling point.

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Step 2: Read the temperatures from the graph

Look at the first plateau (melting):

- It starts around minute 5 and ends around minute 9.
- The temperature during this plateau is 70°C → that’s the melting point.

Now look at the second plateau (boiling):

- Starts around minute 14, ends around minute 18.
- Temperature is 140°C → that’s the boiling point.

So, the substance in the experiment has:
- Melting point = 70°C
- Boiling point = 140°C

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Step 3: Compare with the table

Here’s 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 ✔

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Final Answer:

Foosium