To address the given question, we need to analyze the provided data for compounds A and B, specifically focusing on their temperature change and type of intermolecular forces (IMF).
### Step-by-Step Solution:
1. Identify Temperature Changes:
- Compound A: Temperature change = -12.5°C
- Compound B: Temperature change = -9.2°C
2. Identify Intermolecular Forces (IMF):
- Both Compound A and Compound B are indicated to have Dispersion Forces (DF) as their type of IMF.
3. Compare Temperature Changes:
- For compound A, the temperature decrease is greater (-12.5°C) compared to compound B (-9.2°C).
4. Understand the Relationship Between Temperature Change and Evaporation:
- A greater temperature decrease generally indicates a faster rate of evaporation. This is because the loss of heat (temperature decrease) is associated with the energy required for molecules to transition from liquid to gas (evaporate).
5. Determine the Likely Cause of the Difference:
- Since both compounds have the same type of intermolecular forces (DF), the primary difference between them would be the amount or strength of these forces.
- The dispersion forces (DF) are weak intermolecular forces that depend on the size and shape of the molecules as well as the molecular mass. A larger molecule or one with a greater surface area can have stronger dispersion forces.
6. Conclusion:
- Since compound A evaporates faster (greater temperature change), it likely has weaker dispersion forces compared to compound B.
- Therefore, the most likely cause for the difference in the rate of evaporation is that "The molecules have different amounts of dispersion forces."
By following the logical steps above, we reach the conclusion that the difference in the rate of evaporation between compounds A and B is due to the molecules having different amounts of dispersion forces.
