100 g of ice at `-15^@C` was heated. The rise in temperature of ice was plotted against the heat given to ice. Which of the following graphs (Fig. 6.2) correctly depicts this behaviour?

Options

A.
B.
C.
D.

Answer

To solve the question regarding the heating of 100 g of ice at -15°C and the corresponding graph of rise in temperature against heat given, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Initial Conditions**:
- The initial temperature of the ice is -15°C.

2. **Heating the Ice**:
- When heat is applied to the ice, the first change will be the increase in temperature from -15°C to 0°C. This process involves heating the ice without changing its state.

3. **Phase Change at 0°C**:
- Once the temperature reaches 0°C, the ice begins to melt. During this phase change, the temperature remains constant at 0°C until all the ice has melted into water. This means that even though heat is being added, the temperature does not increase during this time.

4. **Heating the Water**:
- After all the ice has melted, the temperature of the water (which is now at 0°C) will start to rise as more heat is added. The temperature will continue to increase until it reaches the boiling point of water (100°C).

5. **Graph Representation**:
- The graph will show an initial linear increase in temperature as heat is added from -15°C to 0°C. At 0°C, the graph will flatten out (indicating a phase change) as the ice melts. After the phase change, the graph will again show a linear increase in temperature as the water is heated.

6. **Select the Correct Graph**:
- Based on the described behavior, the correct graph will depict a rise in temperature from -15°C to 0°C, followed by a flat line at 0°C during melting, and then a rise in temperature as the water is heated.

### Conclusion:
The correct graph that depicts this behavior is **Option 4**.