II III I C. Johannesson The Nature of Solutions Solutions

C. Johannesson Mixtures  Can be divided into two categories: Heterogeneous (different throughout) –Suspensions –Colloids Homogeneous (same throughout) –Solutions

C. Johannesson Mixtures  Can also be classified according to the size of their solute. Solution < 1nm Colloid nm Suspension >1000nm FYI: 1nm = 1 x m = m (in other words…really small!)

C. Johannesson Types of Mixtures  Solutions, Colloids, and Suspensions  (based on size of solute)

C. Johannesson Suspensions  Particles in a suspension settle out.  Examples: oil and water, paint, mud in water, flour in water

C. Johannesson Colloids  Particles in a colloid scatter light, but are usually not visible to the human eye.  Examples: Milk, fog, mayonaise, shaving cream, jelly, blood

C. Johannesson Solution  Particles in a solution are never visible, and do not scatter light.  Example: sugar and water

C. Johannesson Tyndall Effect  Scattering of light by colloidal particles Used to distinguish a colloid from a solution

C. Johannesson Definitions  Solution -  Solution - homogeneous mixture made by dissolving one substance (solute) into another substance (solvent). Solvent Solvent – substance that dissolves the solute Solute Solute - substance being dissolved

C. Johannesson Solutions  The solute dissolves in the solvent!

C. Johannesson Solutions Solute + Solvent = Solution This makes a solution!

C. Johannesson Solubility  Solubility is the measure of how “dissolvable” a substance is. (maximum grams of solute that will dissolve in 100 g of solvent at a given temperature)  Some substance will not dissolve  insoluble  Some will dissolve  Soluble

C. Johannesson Factors that Affect Solubility  Temperature solids, liquids  increased temperature leads to an increase in solubility gases  increase in temperature leads to a decrease in solubility  What does this mean? Solids dissolve better at higher temperatures while gases dissolve better at lower temperatures!

C. Johannesson Solubility Curve  shows the dependence of solubility on temperature  As temperature increases, the solubility of most solids increases and the solubility of gases decreases.

C. Johannesson Factors that Affect Solubility  Pressure Affects the solubility of gases in liquids *Gases dissolve better at higher pressures!

C. Johannesson Factors that Affect Solubility  Nature of the Solute Water is called the universal solvent because it is a polar molecule (making it easy to dissolve most things). Polar solutes dissolve in polar solvents. Non-polar solutes dissolve in non-polar solvents. “Like dissolves Like”

C. Johannesson Factors that Affect Solubility NONPOLAR POLAR “Like Dissolves Like”

C. Johannesson Types of Solutions  When you dissolve one substance into another, a limited amount of solute can be dissolved in a given amount of solvent.  Three types of Solutions can be made: Unsaturated Saturated Supersaturated

C. Johannesson Types of Solutions SATURATED SOLUTION no more solute dissolves UNSATURATED SOLUTION more solute dissolves SUPERSATURATED SOLUTION becomes unstable, crystals form concentration

C. Johannesson Solubility Curve  Where they are on a solubility curve

C. Johannesson Factors affecting the RATE of dissolving  Temperature  Heat it!  Surface Area  Crush it!  Agitation  Stir it!

C. Johannesson Electrolytes Strong Electrolyte Non- Electrolyte All of it Ionizes Bright Light - + salt - + sugar None of it ionizes No Light - + acetic acid Weak Electrolyte Some of it ionizes Weak Light

C. Johannesson Units of Concentration: 1. Percent by Mass % = mass of solute x 100 mass of solute + solvent

C. Johannesson Example: A solution of NaCl is prepared by dissolving 5.0g of salt in 550.5g of water. What is the percent by mass concentration of this solution?

C. Johannesson Example: A solution of sugar water is prepared by dissolving grams of glucose in 1775 grams of water. What is the percent by mass concentration of this solution?

C. Johannesson Units of Concentration: 2. Molarity M = moles solute Liters of solution

C. Johannesson Example - What is the molarity of a solution composed of 5.85g KI dissolved in 0.125L of solution?

C. Johannesson Example How many moles of solute are present in 10.2 liters of a 3.5 Molar solution?

C. Johannesson Units of Concentration: 3. Molality m = moles solute kg of solvent

C. Johannesson Example - What is the molality of a solution composed of 2.55g of acetone (CH 3 ) 2 CO, dissolved in 200.0g water?

C. Johannesson Example: If a 6.0 molal solution contains 7.19 moles of solute, what is the mass, in kg, of solvent?