Describe how waters molecular structure gives it the properties of expansion and high solubility.

Due to polarity and ability to form hydrogen bonds, water is an excellent solvent and it can dissolve many different kind of molecules. Water is good at dissolving polar molecules and ions but poor at dissolving non-polar molecules.

Water molecules are polar, with partially positive charge on the hydrogen, a partially negative charge on the oxygen and a bent overall structure. Because of polarity water can form electrostatic interactions with other polar molecules and ions and these interaction lead to formation of hydration shell around the solute particles.

Now what is a hydration shell? let us understand this with an example of NaCl. If you stir table salt into water, the crystal lattice of Nacl will begin to dissociate into Na+ and Cl- ions. Water molecules will form hydration shell by surrounding Na+ with partially negative charged ion Oxygen and surrounding Cl-  by partially positive ion Hydrogen. As the process continues all the table salt crystals are surrounded by hydration shells and dispersed in solution.

Non polar molecules like Fat and oil do not interact with water or form hydration shell.