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Factors affecting Solubility Get out your lab to complete it Solutions are Mixtures The Solution Process Factors Affecting the Rate of Dissolving 1) Crushing/Grinding It reduces the particle size and increases the surface area of the solute exposed to the solvent 2) Agitation (stirring) - Brings “fresh” solvent into contact with the solute. (more collisions) 3) Heating the solvent- Increases the kinetic energy (moving faster) of the solvent molecules causing more frequent collisions between the solvent and solute. Solubility and Factors affecting solubility Solubility- the amount of a substance required to form a saturated solution with a specific amount of solvent at a specific temp. ex: the solubility of sugar in water is 204 g/100 ml of water at 20oC. The Solution Process Consider a sugar solute with a solubility (s) of 204 g per 100ml water. The volume in the diagram is 50 mL. 80g/50ml 102 g/50ml 120g/50ml The Solution Process 1) Saturated solution- a solution that contains the maximum amount of dissolved solute (solubility=204g/100ml) 80g/50ml 102 g/50ml 120g/50ml The Solution Process 2) Unsaturated solution- a solution that contains less solute than a saturated solution (solubility=204g/100ml) 80g/50ml 102 g/50ml 120g/50ml The Solution Process 3) Supersaturated solutiona solution that contains more solute than a saturated solution at the same conditions (solubility=204g/100ml) 80g/50ml 102 g/50ml 120g/50ml Miscibilty The Solution Process Different solvents have the ability to dissolve different amounts of solute. The key is the nature of the solute and the nature of the solvent. The Solution Process C. “Like dissolves like”- solubility of a substance is related to the nature of the solvent. NATURE OF THE SOLUTE POLAR WILL DISSOLVE: Polar substances Ionic compounds NONPOLAR WILL DISSOLVE: Nonpolar molecules covalent compounds Alcohols The Solution Process 1) “like dissolves like”- like refers to the polarity of the solute and solvent a) ex: water will dissolve salt because salt is ionic and water is polar The Solution Process b) ex: oil will not dissolve in water because oil is nonpolar and water is polar The Solution Process miscible (soluble)- Alcohols are miscible in water (dissolves in all proportions) because they are both polar The Solution Process Immiscible (not soluble)- oil is immiscible in water. Solvation: Process that occurs when a solute dissolved. Ions or molecules become completely surrounded by solvent molecules Solubility Curve A graph that indicates how likely a solute is to dissolve in a solvent at any given temperature. (g solute/100 g solvent) Solubility of solids The Solution Process (Temperature) Solubility of a substance is related to temperature of the solution Temperature affects solids and gases differently. Solids increase in solubility Gases decrease in solubility The Solution Process (Pressure) Solubility of a gas is related to pressure being exerted on the solvent Pressure only affects the solubility of gases. Solubility of liquids and solids is not changed by changes in pressure. a) Reason for sodas “bubbling up” when the top of a soda bottle is open. When the bottle is opened, there is a rapid decrease in the pressure and the solubility of carbon dioxide gas in the water is greatly reduced causing the familiar bubbling and foaming. b) This rapid escape of a gas from a liquid is called effervescence. E. Solubility of a substance is related to temperature of the solvent. 1) Gases will always have greater solubility in cold solvents. Types of Mixtures: Solutions Ionic solutions- solutions composed of ions that are free to move throughout the solution a) Electrolyte- Can conduct an electric current; acids, bases & salts Ex: NaCl in water Ex: Tap water Solutions in which the solute is composed of neutral molecules Non-electrolyte- cannot conduct electric currents; covalent compounds (except acids) Ex: Sugar in pure water The Solution Process Water molecules are in continuous motion. When a solute is added the water molecules will collide with it. The Solution Process The water molecules attract the solute particles and the particles will break away. The Solution Process Solvation: The process that occurs when a solute dissolves – ions or molecules become solvated or surrounded by solvent molecules