[Raffy03]

We did an experiment in class re: the solubility of the isomers of Butanol in water. I've already done my research and basically it said that depending on the molecular structure (shape) of the isomers, the hydrophobic region (carbon chain) can hinder the solubility of the isomer. Branching therefore, increases solubility; as the larger the surface area of the hydrophobic region makes it harder for the isomer to be dissolved in water.

But what I don't understand, no matter how hard I try and do research, why does adding more water to the isomers of Butanol, make it soluble? Attached is a picture of the results from the experiment. I=Insoluble, S=Soluble.

https://imgur.com/a/vMrUcPv

[Borek]

Seems like you are confusing solubility with amount of substance dissolved.

Adding more water doesn't make something soluble. Solubility (typically expressed in units like g/100g of solvent, or equivalent) is an intensive property, doesn't depend on the amount of substance.

However, assuming you take the same amount of several substances (say, 1g of each), the less soluble substance is, the more water you need to dissolve the substance completely. It doesn't mean it got more soluble, amount of substance dissolved is an extensive property, it depends on the amount of solvent.

[Aldebaran]

@OP
Wikipedia has a useful article relevant to this question. Look up ‘solvation ’.