Properties of Solutions

Do Now: Get out your memory game from yesterday and play with your group for 10 minutes—there will be a memory challenge tomorrow!

Notes Today: Write down what you believe is most important—you will have one minute per slide just for writing before I explain the content! These are the first notes of the 9 weeks!

Classification of Matter Solutions are homogeneous mixtures

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

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

Go here… http://www.dhmo.org/facts.html Read several sections of information You have five minutes…

Stop n’ Jot Tell me all that you know about dihydrogen monoxide! We know…

Water’s Solvent Interactions The oxygen (slightly negative) end of the water molecule is attracted to the positive ion of a salt.

Water’s Solvent Interactions The hydrogen (slightly positive) end of the water molecule is attracted to the negative ion of a salt.

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

Solubility Chart

Definition of Electrolytes and Nonelectrolytes 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.

Electrolytes vs. 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.

Try to classify the following substances as electrolytes or nonelectrolytes… Pure water Tap water Sugar solution Sodium chloride solution Hydrochloric acid solution Lactic acid solution Ethyl alcohol solution Pure sodium chloride

Answers to Electrolytes NONELECTROLYTES: Tap water (weak) NaCl solution HCl solution Lactate solution (weak) Pure water Sugar solution Ethanol solution Pure NaCl

Colligative Properties Colligative properties are those that depend on the concentration of particles in a solution, not upon the identity of those particles. Boiling Point Elevation Freezing Point Depression Osmotic Pressure

Freezing Point Depression Each mole of solute particles lowers the freezing point of 1 kilogram of water by 1.86 degrees Celsius. Boiling Point Elevation Each mole of nonvolatile solute particles raises the boiling point of 1 kilogram of water by 0.51 degrees Celsius.

Calculations of Solution Concentration

Ga Standards Students know the definitions of solute and solvent. Students know how to calculate the concentration of a solute in terms of molarity, prepare a properly labeled solution, and how to apply the concept of molality.

Calculations of Solution Concentration: Molarity Molarity is the ratio of moles of solute to liters of solution

A Simplifying Assumption 1 ml of water = 1 gram of water 1000 ml of water = 1 liter = 1000 grams Assume that solutions with water as the solvent have the density of pure water (1 mL = 1 gram) It’s not true, but it’s close enough 