Properties of Solutions

Classification of Matter Solutions Solutions are homogeneous mixtures

Solute A solute is the dissolved substance in a solution. A solvent is the dissolving medium in a solution. Solvent Salt in salt water Sugar in soda drinks Carbon dioxide in soda drinks Water in salt waterWater in soda

“Like Dissolves Like” Fats Fats Benzene Benzene Steroids Steroids Hexane Hexane Waxes Waxes Toluene Toluene Inorganic Salts Water Water Sugars Sugars Small alcohols Small alcohols Acetic acid Acetic acid Polar and ionic solutes dissolve best in polar solvents Nonpolar solutes dissolve best in nonpolar solvents

Solubility Trends  The solubility of MOST solids increases with temperature.  The rate at which solids dissolve increases with increasing surface area of the solid.  The solubility of gases decreases with increases in temperature.  The solubility of gases increases with the pressure above the solution.

Therefore… Solids tend to dissolve best when: o Heated o Stirred o Ground into small particles Gases tend to dissolve best when: o The solution is cold o Pressure is high

An electrolyte is: A substance whose aqueous solution conducts an electric current. A nonelectrolyte is: A substance whose aqueous solution does not conduct an electric current. Definition of Electrolytes and Nonelectrolytes

The ammeter measures the flow of electrons (current) through the circuit. If the ammeter measures a current, and the bulb glows, then the solution conducts. If the ammeter fails to measure a current, and the bulb does not glow, the solution is non-conducting. Electrolytes vs. Nonelectrolytes

1.Pure water 2.Tap water 3.Sugar solution 4.Sodium chloride solution 5.Pure sodium chloride 1.Pure water 2.Tap water 3.Sugar solution 4.Sodium chloride solution 5.Pure sodium chloride Try to classify the following substances as electrolytes or nonelectrolytes…

ELECTROLYTES: NONELECTROLYTES: Tap water (weak) NaCl solution Pure water Sugar solution Pure NaCl Answers to Electrolytes

Suspensions and Colloids Suspensions and colloids are NOT solutions. Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred. Colloids: The particle is intermediate in size between those of a suspension and those of a solution.

The Tyndall Effect Colloids scatter light, making a beam visible. Solutions do not scatter light. Which glass contains a colloid? solution colloid

Making solutions In order to dissolve - the solvent molecules must come in contact with the solute. Stirring moves fresh solvent next to the solute. The solvent touches the surface of the solute. Smaller pieces increase the amount of surface of the solute.

O 2- H+H+ H+H+ H2OH2O  ++ ++ Water Molecule Water is a POLAR molecule

Water Molecule O 2- H+H+ H+H+ Water is a POLAR molecule H2OH2O  ++ ++ Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 8

Dissolving of solid NaCl

Polar water molecules interact with positive and negative ions Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 468 Animation

Solvation Solvation – Solvation – the process of dissolving solute particles are separated and pulled into solution solute particles are surrounded by solvent particles

Dissolving of NaCl Timberlake, Chemistry 7 th Edition, page 287 HH O Na Cl hydrated ions

Dissociation Reactions Write dissociation reactions for the following ionic compounds when dissolved in water – CaBr 2  – Mg(NO 2 ) 2  – Na 3 PO 4  – Ba 3 P 2 

Solutions -- Definitions Saturated – a solution that contains the maximum amount of solute that will dissolve. Unsaturated – a solution that contains less than the maximum amount of solute that will dissolved Supersaturated – a solution that contains more solute than will dissolve

Solubility Chart