During vapourisation
I. change of state from liquid to vapour state occurs.
II. temperature remains constant.
III. both liquid and vapour states coexist in equilibrium.
IV. specific heat of substance increases. Correct statements are

Options

A. I, II and IV
B. II, III and IV
C. I, III and IV
D. I , II and III

Answer

To solve the question regarding the correct statements during vaporization, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Understanding Vaporization**:
- Vaporization is the process in which a liquid changes into a vapor (gas) when heat is applied. This can occur through boiling or evaporation.

2. **Analyzing Statement I**:
- **Statement I**: "Change of state from liquid to vapor state occurs."
- **Analysis**: This statement is true because during vaporization, the liquid indeed changes its state to a vapor.

3. **Analyzing Statement II**:
- **Statement II**: "Temperature remains constant."
- **Analysis**: This statement is also true. During the phase change of vaporization, the temperature of the liquid remains constant until all the liquid has turned into vapor, despite the continuous addition of heat.

4. **Analyzing Statement III**:
- **Statement III**: "Both liquid and vapor states coexist in equilibrium."
- **Analysis**: This statement is true as well. During vaporization, especially at boiling point, both the liquid and vapor phases coexist in equilibrium until the entire liquid has vaporized.

5. **Analyzing Statement IV**:
- **Statement IV**: "Specific heat of substance increases."
- **Analysis**: This statement is false. The specific heat does not increase during vaporization; rather, it is a property of the substance that remains constant at a given temperature. The temperature remains constant during the phase change, so the specific heat cannot increase.

### Conclusion:
The correct statements during vaporization are:
- Statement I: True
- Statement II: True
- Statement III: True
- Statement IV: False

Thus, the correct statements are I, II, and III.

### Final Answer:
The correct statements are I, II, and III.

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