- since electrons are attracted to O, the other side of H atoms are free from -ve charge
- +ve side of H atoms are attracted to -ve side of O atoms in other molecules
- causes higher melting and boiling points, expansion when frozen (hexagonal structure), high latent heat, specific heat capacity, solvent properties
+- hydroxyls (OH) dissolve easily in H2O due to H-bonding
## Solubility
- "like dissolves like" - polar/non-polar substances
- polar gases dissolve easily as well e.g. CO2 enables submarine photosynthesis
- solubility is useful for living organisms (blood etc)
- surfactants - polar + non-polar ends, dissolve in both oil + water
+- solubility depends on polar / non-polar proportion
## Measuring solubility
- heterogeneous (mixtures) or homogeneous (solutions)
- more soluble at higher temperatures
- solubility measured in g / 100g H2O
+## Heating and cooling
+- solubility $\propto$ temperature, so when substance is cooled, the solute is precipitated out into crystals
+
## Crystallisation
- used to isolate substances based on $\Delta$ solubility in substances
- can cause saturated or supersaturated solutions (unstable)
## Concentration
- amount of solute per volume of solvent - e.g. g / L
- relative terms - "concentrated" or "dilute"
+- mg / L = ppm = $\mu$g / g