Which of the following statements is/are incorrect?
I. Temperature does not change during the change of a state.
II. Dry ice gets converted directly into gaseous state at 1 atm pressure.
III. Lower boiling point of a liquid indicates weaker intermolecular forces.
IV. Latent heat of fusion is generally higher than the latent heat of vaporisation for a substance.

Options

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

Answer

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

### Step 1: Analyze Statement I
**Statement I:** "Temperature does not change during the change of a state."
- This statement is **true**. During a phase change (like melting or boiling), the temperature remains constant while the substance absorbs or releases heat to change its state.

**Hint:** Remember that during phase changes, energy is used to overcome intermolecular forces rather than increasing temperature.

### Step 2: Analyze Statement II
**Statement II:** "Dry ice gets converted directly into gaseous state at 1 atm pressure."
- This statement is **true**. Dry ice (solid carbon dioxide) sublimates directly into gas at atmospheric pressure (1 atm) and at a temperature of -78.5°C.

**Hint:** Recall that sublimation is the process where a solid turns directly into a gas without becoming a liquid.

### Step 3: Analyze Statement III
**Statement III:** "Lower boiling point of a liquid indicates weaker intermolecular forces."
- This statement is **true**. A lower boiling point suggests that less energy is required to overcome the intermolecular forces, indicating that these forces are weaker.

**Hint:** Consider how boiling points relate to the strength of intermolecular forces; weaker forces require less energy to break.

### Step 4: Analyze Statement IV
**Statement IV:** "Latent heat of fusion is generally higher than the latent heat of vaporization for a substance."
- This statement is **false**. The latent heat of vaporization (energy required to convert a liquid into gas) is generally higher than the latent heat of fusion (energy required to convert a solid into liquid). This is because breaking the intermolecular forces in a liquid to form a gas requires more energy than changing a solid to a liquid.

**Hint:** Think about the energy needed to change states; vaporization involves a larger change in energy compared to fusion.

### Conclusion
The only incorrect statement among the options provided is **Statement IV**.

### Final Answer
**Incorrect Statement:** IV. Latent heat of fusion is generally higher than the latent heat of vaporization for a substance.