What are polar and non-polar molecules?
→ A polar molecule is a molecule which contains both negative and positive charges in one moleucle, although they're not that strong. You might say they're haf positive and half negative (but not neutral).
→ A non-polar molecule is a molecule which is either sharing an equivalent amount of electrons between the atoms inside it, or because it has a symmetrical, linear geometry. In these molecules, there is also no dipole.
How does that affect the water's properties?
So, just a tiny atomic-sized change can influence on how the water interacts with their environment. No matter how small the change is, if it changes a basis of the waters properties, it'll affect the properties itself, of course.
Moving on to the changes. What are some noticable changes?
We can see in the 2 explanations above, that, there is a difference between bonding and atom aranging in non-polar and polar molecules. This can affect things such as surface tension, and the hydrogen bonds.
We also see there is a difference in the charge of atoms, and therefore the charge of the molecule, which can affect conductivity and the interaction of water with other molecules specially ions.
→ There will also be more physical changes, rather than only chemical ones, but the 2 above are the most noticable and probably important ones.
Hope it helped,
BioTeacher101