Let’s solve this step by step.
We are given a phase change diagram (temperature vs. time) and asked to fill in blanks based on what happens during heating of a substance. We also need to identify which substance from the table matches the data.
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Step 1: Understand the graph
The graph shows temperature rising over time as heat is added at a constant rate.
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Point A: Start — solid state, temp ~30°C
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A to B: Solid warming up
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B to C: Flat line → melting (solid turning to liquid). Temp stays at 70°C → so melting point = 70°C
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C to D: Liquid warming up
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D to E: Flat line again → boiling (liquid turning to gas). Temp stays at 140°C → so boiling point = 140°C
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Beyond E: Gas warming up
So:
- Melting point = 70°C
- Boiling point = 140°C
Now look at the table:
| Substance | Melting point | Boiling point |
|---------------|---------------|---------------|
| Bolognium | 20 °C | 100 °C |
| Unobtainium | 40 °C | 140 °C |
| Foosium | 70 °C | 140 °C |
Only
Foosium has both melting point 70°C and boiling point 140°C → that must be the substance used.
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Step 2: Fill in the blanks for question 1–22
We’ll go sentence by sentence using science facts about phases and the graph.
> At point A, the beginning of observations, the substance exists in a solid state. Material in this phase has
definite volume and
definite shape.
Solids have fixed shape and volume.
> With each passing minute,
heat energy is added to the substance. This causes the molecules of the substance to
move more rapidly which we detect by a
temperature rise in the substance.
Adding heat makes molecules move faster → temperature rises.
> At point B, the temperature of the substance is
70°C. The solid begins to
melt.
From graph, flat part starts at 70°C → melting begins.
> At point C, the substance is completely
liquid or in a
liquid state. Material in this phase has
definite volume and
indefinite shape.
Liquids have fixed volume but take shape of container.
> The energy put to the substance between minutes 5 and 9 was used to convert the substance from a
solid to a
liquid.
That’s the melting plateau (B to C), from min 5 to 9.
> Between 9 and 13 minutes, the added energy increases the
temperature of the substance.
Graph shows temp rising from C to D → liquid heating up.
> During the time from point D to point E, the liquid is
boiling.
Flat line at 140°C → boiling.
> By point E, the substance is completely in the
gas phase. Material in this phase has
indefinite volume and
indefinite 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.
That’s the boiling plateau (D to E).
> Beyond point E, the substance is still in the
gas phase, but the molecules are moving
faster as indicated by the increasing temperature.
Temp rising again → molecules speeding up.
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Step 3: Answer question 23
Which substance? As determined earlier —
Foosium, because its melting point (70°C) and boiling point (140°C) match the plateaus on the graph.
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Final Answer:
Foosium
Parent Tip: Review the logic above to help your child master the concept of phase change diagram worksheets.
