Properties of Solutions

CA StandardsStudents know the definitions of solute and solvent.

Students know how to describe the dissolving process at the molecular level by using the concept of random molecular motion.

Students know temperature, pressure, and surface area affect the dissolving process.

Classification of MatterSolutions are homogeneous mixtures

SoluteA 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 drinksCarbon dioxide in soda drinks

Water in salt water Water in soda

“Like Dissolves Like”

Fats Benzene Steroids Hexane Waxes Toluene

Polar and ionic solutes dissolve best in polar solvents

Nonpolar solutes dissolve best in nonpolar solvents

Inorganic Salts Water Sugars Small alcohols Acetic acid

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:

o Heatedo Stirredo Ground into small particles

Gases tend to dissolve best when:o The solution is cold

o Pressure is high

Solubility Chart

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 water2.Tap water3.Sugar solution4.Sodium chloride solution5.Hydrochloric acid solution6.Lactic acid solution7.Ethyl alcohol solution8.Pure sodium chloride

Try to classify the following substances as electrolytes or

nonelectrolytes…

ELECTROLYTES: NONELECTROLYTES:

Tap water (weak) NaCl solution HCl solution Lactate solution (weak)

Pure water Sugar solution Ethanol solution Pure NaCl

Answers to Electrolytes

Colligative PropertiesColligative 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 DepressionEach mole of solute particles lowers the freezing point of 1 kilogram of water by 1.86 degrees Celsius.

Each mole of nonvolatile solute particles raises the boiling point of 1 kilogram of water by 0.51 degrees Celsius.

Boiling Point Elevation