WHY should a scientist modify an experiment, after initial data has been documented and analyzed?

I think  they would modify it because maybe they realized they messed some thing up or forgot to write down data.

Explanation:

clouds form

solid ice forms on leaves.

water droplets form on grass.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).