Wavelength is the distance between two identical adjacent points in a wave. This means that it is the distance between two adjacent compressions or two adjacent rarefactions.
Wavelengths are inversely related to frequency because the longer the wavelength, the less the number of wave cycles per second.
The isopropanol evaporated while the water did not because the molecules don't stick together as strongly as the molecules in the water do. The water would need more energy transferred in, in order to evaporate.
