Solubility is defined as… the ability of a solute to dissolve in a solvent.

Solutions Vocabulary Polar compound – a covalent compound in which electrons are not equally shared (Ex. Water) This happens when the electronegativity of the elements are unequal Non-polar compound – a covalent compound in which electrons are equally shared between atoms (Ex. chlorine gas)

Solubility Rules We’ve already talked about solubility rules in terms of ionic compounds (see reference materials) Note: ionic compounds only dissolve in polar solvents – they won’t dissolve in non-polar substances For covalent compounds, we follow the rule “like dissolves like” – i.e. polar substances dissolve polar substances, and nonpolar substances dissolve nonpolar substances – that’s why oil won’t dissolve in water!

Electrolytes Electrolyte – a substance that when dissolved in water will dissociate into ions, which can conduct electricity In order for a substance to be considered an electrolyte, it must contain ions Strong ElectrolytesWeak ElectrolytesNonelectrolytes Ionic Compounds Salt water Strong Acids & Bases Hydrochloric acid Potassium hydroxide Tap Water Weak Acids & Bases Acetic acid Citric acid Distilled water Non-polar compounds Gasoline Aqueous sugar solutions Sweet Tea PhET

Factors Affecting Solubility Rate of Dissolution – speed of the solute dissolving (Solids only) 1.Agitation/ Stirring – will help the solute dissolve faster. Increases the rate. 2.Particle size – crushing or grinding the solute will help it dissolve faster. Increases the rate. 3.Heat – will help the solute dissolve faster. Increases the rate.

Factors Affecting Solubility Amount of Dissolution- how much solute can dissolve 1.Amount of solvent 2.Temperature For solids: High temp = higher solubility For gases: high temp = lower solubility 3.Pressure (gases only) Higher pressure = higher solubility

Types of Solutions 1.Saturated solution- a solution where a solvent can dissolve no more solute and additional amounts of it will appear as a solid. Full capacity dissolved.

Types of Solutions 2. Unsaturated solution – a solution that is capable of dissolving more solute.

Types of Solutions 3. Supersaturated solution – solvent holds more solute than is normally possible at that temperature. These solutions are usually unstable and can crystallization can occur by adding a seed crystal.

Solubility Curves Any amount of solute below the curved line indicates solution is unsaturated at that temperature (more solute can be dissolved) Any amount of solute on the curved line indicates solution is saturated (full capacity of solute that can dissolve) Any amount of solute above the curved line in which all the solute is dissolved shows the solution is supersaturated (more than the full capacity of solute has dissolved due to heating)

Questions to think about 1.How do you make a supersaturated solution? What can you do to the solution to tell if it is supersaturated? 2.What is the difference between the gas curve and the solid curve?

1)If you added 70g of KNO 3 to100g of water at 44 O C, what type of solution would you produce? 2)If you added 50g of KNO 3 to 100g of water at 50 O C, what type of solution would you produce? 3)If you add 50 g of KCl to 100g of water at 50°C, what type of solution would you produce?