- 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
+
+## Molarity
+- special concentration unit in mol / L (abbbreviation M)
+$$c={n \over v}$$
+
+$$c_1v_2=c_2v_2=n\quad\leftarrow(\operatorname{constant})$$
+
+| Quantity | Symbol | Unit |
+| ---------------------- | ------- | ------------- |
+| molar mass | $M$ | g / mol |
+| molar concentration | $c$ | mol / L ($M$) |
+| specific heat capacity | $c$ | J / g / K |
+
+## Precipitation reactions
+Ions in solution combine to form a new compound.
+Occurs when concentration exceeds solubility.
+Precipitation reactions happen when water cannot dissociate ionic lattice structure.
+Precipitate (product):
+
+- generally insoluble in water
+- forms as solid particles that settle
+- forms from compounds insoluble in water
+
+All group 1 ions are soluble.
+
+**Ions swap between reactants**
+
+## Ionic equations
+
+Used when a salt (ionic) dissolves into constituent ions.
+"Spectator" ions - ions that do not dissolve or precipitate in reaction. **Not** included in equations.