Heating Curve Worksheet | PDF - Free Printable

Let's analyze the heating curve provided in the worksheet and answer each question step by step.

---

🔍 Understanding the Heating Curve:

A heating curve shows how the temperature of a substance changes as energy (heat) is added. The graph has temperature on the y-axis and energy added on the x-axis.

Key features:
- Sloped lines: Temperature is increasing → kinetic energy is increasing.
- Flat (horizontal) lines: Phase change is occurring → temperature remains constant; energy is used to break intermolecular forces.

---

📊 Breakdown of the Graph:

- Point a: Solid being heated from -5°C to 5°C.
- Segment b: Flat line at 5°C → melting (solid to liquid).
- Segment c: Liquid being heated from 5°C to 15°C.
- Segment d: Flat line at 15°C → boiling (liquid to gas).
- Segment e: Gas being heated above 15°C.

---

Now, let’s answer each question:

---

1. What is the freezing point of the above substance?

- Freezing point = temperature at which liquid turns to solid.
- This occurs at the same temperature as melting point but in reverse.
- Melting happens at 5°C, so freezing point is also 5°C.

✔ Answer: 5°C

---

2. What is the melting point of the above substance?

- Melting occurs during segment b, where the temperature stays at 5°C while the solid turns to liquid.

✔ Answer: 5°C

---

3. What is the boiling point of the above substance?

- Boiling occurs during segment d, where the temperature stays at 15°C while liquid turns to gas.

✔ Answer: 15°C

---

4. What letter represents the temperature range where the solid is being heated?

- Before melting, the solid is being warmed up.
- This is segment a, from -5°C to 5°C.

✔ Answer: a

---

5. What letter represents the temperature range where the liquid is being heated?

- After melting and before boiling, the liquid is being heated.
- This is segment c, from 5°C to 15°C.

✔ Answer: c

---

6. What letter represents the temperature range where the gas is being heated?

- After boiling, the gas is being heated.
- This is segment e, after 15°C.

✔ Answer: e

---

7. What letter represents the melting of the solid?

- Melting occurs at constant temperature (phase change), shown by segment b.

✔ Answer: b

---

8. What letter(s) show a change in kinetic energy?

- Kinetic energy increases when temperature increases (because molecules move faster).
- This happens during sloped segments where temperature rises:
- a (solid heating)
- c (liquid heating)
- e (gas heating)

- In flat segments (b and d), energy goes into breaking bonds (potential energy), not increasing motion.

✔ Answer: a, c, e

---

9. What letter represents condensation?

- Condensation is the reverse of boiling — gas turning into liquid.
- But this heating curve shows heating, so it only goes forward (solid → liquid → gas).
- Condensation does not occur in this graph because no cooling is shown.

⚠️ However, if we consider what would be the reverse process, then d is boiling, so condensation would be the reverse of d.

But since the graph shows heating, condensation is not represented.

✔ Answer: None (or "Not shown")

> ⚠️ Note: Since the graph is a heating curve, it only shows warming and phase changes in the direction of increasing energy. Condensation is a cooling process and is not present here.

---

✔ Final Answers:

1. 5°C
2. 5°C
3. 15°C
4. a
5. c
6. e
7. b
8. a, c, e
9. None / Not shown

---

Let me know if you'd like this explained with a diagram or further details!