What is solubility? Explain the factors that affect solubility.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define in one line. Solubility is the number of grams of solute that dissolve in 100 g of solvent to form a saturated solution at a given temperature.
2 · Nature of solute and solvent. Like dissolves like: salt dissolves in polar water; grease dissolves in non-polar kerosene.
3 · Temperature.
Endothermic dissolving: solubility rises with temperature (KNO₃)
Exothermic dissolving: solubility falls with temperature (Ca(OH)₂)
Gases: solubility falls as temperature rises
4 · Pressure. Affects gases only: the higher the pressure above the liquid, the more gas dissolves.
5 · Real-life link. Soda bottles fizz when opened, and fish rise to the surface of warm ponds.
6 · Close in one line. Thus solubility depends on the substances, the temperature and, for gases, the pressure.
Scoring tip: Write '100 g of solvent' and 'at a given temperature' in the definition. Give one example for each factor.
