Which of the following statements are correct ?
I. Temperature changes during the change of a state.
II. Dry ice gets converted directly into gaseous state under normal atmospheric conditions.
III. Higher boiling point of liquid indicates weaker intermolecular forces.
IV. Latent heat of vaporisation is generally higher than the latent heat of fusion for a substance.

Options

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

Explanation

To determine which of the statements are correct, let's analyze each one step by step:

### Step 1: Analyze Statement I
**Statement I:** Temperature changes during the change of a state.

- **Explanation:** When a substance changes its state (e.g., from solid to liquid or from liquid to gas), the temperature remains constant during the phase change. The energy supplied is used to break the intermolecular forces rather than increase the temperature.
- **Conclusion:** This statement is **incorrect**.

### Step 2: Analyze Statement II
**Statement II:** Dry ice gets converted directly into gaseous state under normal atmospheric conditions.

- **Explanation:** Dry ice is solid carbon dioxide (CO2) and it sublimates directly into gas at normal atmospheric pressure without passing through the liquid state. This occurs at temperatures below -78.5 °C.
- **Conclusion:** This statement is **correct**.

### Step 3: Analyze Statement III
**Statement III:** Higher boiling point of liquid indicates weaker intermolecular forces.

- **Explanation:** A higher boiling point indicates that stronger intermolecular forces are present in the liquid. Stronger forces require more energy (higher temperature) to break, leading to a higher boiling point.
- **Conclusion:** This statement is **incorrect**.

### Step 4: Analyze Statement IV
**Statement IV:** Latent heat of vaporization is generally higher than the latent heat of fusion for a substance.

- **Explanation:** The latent heat of vaporization (energy required to convert a liquid into gas) is typically higher than the latent heat of fusion (energy required to convert a solid into liquid). This is because the molecules in the gas state are much farther apart and require more energy to overcome the intermolecular forces.
- **Conclusion:** This statement is **correct**.

### Final Conclusion
The correct statements from the options provided are **Statement II and Statement IV**.

### Summary of Correct Statements:
- **Correct Statements:** II and IV
- **Incorrect Statements:** I and III

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