A block of ice at `-10^@C` is slowly heated and converted to steam at `100^@C.` Which of the following curves represents the phenomenon qualitatively?

Options

A.
B.
C.
D.

Explanation

To solve the problem of heating a block of ice at -10°C to steam at 100°C, we will analyze the process step by step and represent it qualitatively on a graph.

### Step 1: Heating the Ice from -10°C to 0°C
- **Initial State**: The block of ice is at -10°C.
- **Process**: As we apply heat, the temperature of the ice increases until it reaches 0°C.
- **Graph Representation**: This part of the graph will show a linear increase in temperature with respect to heat added.

### Step 2: Melting the Ice at 0°C
- **State Change**: At 0°C, the ice begins to melt into water.
- **Process**: During this phase, the temperature remains constant at 0°C while the ice absorbs latent heat.
- **Graph Representation**: This will be a horizontal line on the graph, indicating that temperature does not change while heat is being absorbed.

### Step 3: Heating the Water from 0°C to 100°C
- **Process**: After all the ice has melted, the temperature of the water increases from 0°C to 100°C.
- **Graph Representation**: This part of the graph will again show a linear increase in temperature with respect to heat added.

### Step 4: Converting Water to Steam at 100°C
- **State Change**: At 100°C, the water begins to convert into steam.
- **Process**: During this phase, the temperature remains constant at 100°C while the water absorbs latent heat.
- **Graph Representation**: This will again be a horizontal line on the graph, indicating that temperature does not change while heat is being absorbed.

### Step 5: Final State
- **Final State**: After all the water has turned into steam, the process can continue if more heat is added, but for this question, we stop here.
- **Graph Representation**: The graph ends after the horizontal line at 100°C.

### Summary of the Graph
- The graph will consist of:
1. A sloped line from -10°C to 0°C (heating the ice).
2. A horizontal line at 0°C (melting the ice).
3. A sloped line from 0°C to 100°C (heating the water).
4. A horizontal line at 100°C (boiling the water to steam).

### Conclusion
Based on the above analysis, the correct qualitative representation of the phenomenon is option **A**.

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