This completed phase change worksheet helps students master the transitions between solid, liquid, and gas states through practical question-and-answer exercises.

You’ve uploaded a worksheet titled “Phase Change Questions” that tests understanding of the six main phase changes between solid, liquid, and gas states of matter.

Let’s solve and explain each question step by step.

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## 🔹 PART 1: Multiple Choice / Fill-in-the-Blank

> Instructions: Use the choices in the word bank below to answer the following.
> Word Bank: Melting, Freezing, Boiling, Condensation, Sublimation

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1) The phase change from a solid to a liquid is called ___.

✔ Answer: Melting
🔹 *Explanation:* When a solid gains enough thermal energy, its particles vibrate more and break free from their fixed positions, turning into a liquid. Example: Ice melting into water.

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2) When a liquid changes to a solid it is called ___.

✔ Answer: Freezing
🔹 *Explanation:* Loss of thermal energy causes liquid particles to slow down and form a rigid structure — a solid. Example: Water freezing into ice.

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3) When a cup of liquid water is heated and turned into a gas, it is called ___.

✔ Answer: Boiling
🔹 *Explanation:* Boiling is the rapid vaporization of a liquid when it reaches its boiling point. It’s a type of vaporization, but specifically when bubbles form throughout the liquid. (Note: “Evaporation” also turns liquid to gas, but slowly at the surface; “boiling” is the term used here for heating a cup of water until it turns to steam.)

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4) The phase change where a solid directly turns into a gas is called ___. This is called ___.

✔ Answer: Sublimation
🔹 *Explanation:* Some solids skip the liquid phase entirely when heated. Example: Dry ice (solid CO₂) turns directly into carbon dioxide gas.

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5) The phase change where gas turns to liquid is called ___.

✔ Answer: Condensation
🔹 *Explanation:* When gas loses energy, its particles slow down and come closer together to form a liquid. Example: Water vapor condensing into droplets on a cold glass.

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6) If you *slow down* the particles in a liquid, what phase change occurs?

✔ Answer: Freezing
🔹 *Explanation:* Slowing down particles = removing heat/energy → particles form a solid structure → freezing.

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7) If you *speed up* the particles in a liquid, what phase change occurs?

✔ Answer: Boiling
🔹 *Explanation:* Speeding up particles = adding heat/energy → particles escape as gas → boiling (or evaporation).

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8) In which two phase changes does energy decrease?

✔ Answer: Freezing, Condensation
🔹 *Explanation:* Both involve losing thermal energy:
- Freezing: liquid → solid
- Condensation: gas → liquid
In both, particles slow down and release energy to surroundings.

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9) Which two phase changes occur when you increase the heat?

✔ Answer: Melting, Boiling
🔹 *Explanation:* Adding heat increases particle motion:
- Melting: solid → liquid
- Boiling: liquid → gas

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10) Gas in the clouds is turned into a solid (snow), and forms to liquid. This change is ___.

✔ Answer: Condensation *(and then freezing — but the question likely refers to the first step)*
⚠️ *Clarification:* The question says “gas in the clouds is turned into a solid (snow)” — technically, this involves two steps:
1. Gas → Liquid: Condensation (water vapor → cloud droplets)
2. Liquid → Solid: Freezing (droplets → snow/ice crystals)

But since the question says “this change is ___”, and lists only one blank, it’s likely referring to the initial phase change from gas to liquid (condensation) before freezing. However, if snow forms directly from vapor, that’s deposition (gas → solid). But deposition isn’t in the word bank.

➡️ Since “deposition” isn’t an option, and “condensation” is, and the question mentions “forms to liquid” too, the best fit is Condensation — assuming it's describing the formation of liquid droplets first.

*(Note: If the worksheet intended direct gas→solid, they should have included “deposition”. Given the word bank, “Condensation” is the safest choice.)*

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11) Energy is slowly removed from a liquid. What phase change occurs?

✔ Answer: Freezing
🔹 *Explanation:* Removing energy slows particles → they form a solid → freezing.

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## 🔹 PART 2: Diagram Matching

> Instructions: For each arrow, write the appropriate phase change represented.

The diagram shows a cycle:

```
Melting
Solid ---------> Liquid
^ |
| | Boiling
| Freezing v
| Gas <-------- Condensation
| ^
| Sublimation |
+---------------+ Deposition (not labeled)
```

*(Note: The diagram actually shows arrows for:*

- Solid → Liquid = Melting
- Liquid → Gas = Boiling
- Gas → Liquid = Condensation
- Liquid → Solid = Freezing
- Solid → Gas = Sublimation
- Gas → Solid = Deposition — though not labeled in your image, it’s implied by the reverse of sublimation.

But based on your image description and typical worksheets, here are the correct labels for each arrow:

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✔ Arrow from Solid to Liquid → Melting
✔ Arrow from Liquid to Gas → Boiling
✔ Arrow from Gas to Liquid → Condensation
✔ Arrow from Liquid to Solid → Freezing
✔ Arrow from Solid to Gas → Sublimation

*(Note: Your image may not show “Gas to Solid”, but if it did, it would be “Deposition” — which isn't in the word bank. So we stick to the 5 listed.)*

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## ✔ FINAL ANSWERS SUMMARY:

Part 1:

1. Melting
2. Freezing
3. Boiling
4. Sublimation
5. Condensation
6. Freezing
7. Boiling
8. Freezing, Condensation
9. Melting, Boiling
10. Condensation *(best fit given word bank)*
11. Freezing

Part 2 (Diagram Arrows):

- Solid → Liquid: Melting
- Liquid → Gas: Boiling
- Gas → Liquid: Condensation
- Liquid → Solid: Freezing
- Solid → Gas: Sublimation

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## 🧠 BONUS TIP: Mnemonic!

To remember the phase changes:

> MELT = Solid → Liquid
> FREEZE = Liquid → Solid
> BOIL = Liquid → Gas
> CONDENSE = Gas → Liquid
> SUBLIME = Solid → Gas
> DEPOSIT = Gas → Solid *(not in word bank)*

Energy added → Melting, Boiling, Sublimation
Energy removed → Freezing, Condensation, Deposition

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Let me know if you’d like a printable version or flashcards for these! 😊