Solutions Are homogeneous mixtures A physical combination of

Solutions • Are homogeneous mixtures • A physical combination of two or more substances, that appear to be only one

• The parts of a solution are referred to as the solute and the solvent. • The solute is the part that disappears into the solvent. (dissolves into the solvent) • The solvent is the part that does not disappear.

Types of Solutions • If you combine three states of matter in every possible way, you get 9 types.

Type of solution example solute solvent Solid in liquid Tincture sea water betadiene salt iodine water alcohol Solid in a solid alloys ( Brass) Solid in gas Gas in liquid or Or smoke Real fine dust blood soda zinc copper fine wood air CO 2 oxygen water blood serum Gas in gas air oxygen Gas in solid air freshener Gas mask odors tear gas baking soda charcoal alcohol water air mercury silver Liquid in liquid vodka Liquid in gas humid air Liquid in solid amalgam ( Tooth filling ) nitrogen

• Aqueous solutions are ones in which water is the solvent. • Tincture is a solution, in which alcohol is the solvent • Miscible – liquids that are mutually soluble in each other. Alcohol and water • Immiscible – liquids that do not dissolve in each other. Oil and water

Solubility • How much of a solute that can dissolve in a given amount of solvent. • Normally expressed as grams of solute per 100 grams of solvent. But can be others • a Saturated solution, Contains the maximum amount of solute possible. • Unsaturated does not

• Supersaturated contains more solute than a normal saturated solution. They are hard to make and very unstable. The extra solute precipitates out very easily

The Dissolving Mechanism • Three things have to happen in order for stuff to • • • dissolve. 1 The solvent must separate to allow the solute to enter. ( water moves aside when you jump in) that requires work, energy. 2 The solute must break apart. (dissociation) That also requires energy. 3 The solute and solvent must attract each other. That releases energy

• The combination of those 3 energies determines if the dissolving mechanism is endothermic or exothermic. • Endothermic heat must be added to get it to dissolve. • Exothermic will give off heat as it dissolves • Heat of Solution • demos would be good.

Factors affecting Solubility 1 Nature of the solute and solvent are they polar or nonpolar molecules? polarity is back , look over your old notes. likes dissolve likes polars dissolve other polars, nonpolar dissolve nonpolar

Solvation ( Hydration)

2 Temperature – an increase in temp will increase the solubility of substances that have endothermic dissolving mechanism. and decrease the solubility of the exothermic ones. increase in temp increases the solubility of most solids in a liquid you can dissolve more sugar in hot tea than cold tea.

• You have to be able to read this type of graph and apply the information.

An increase in temp decrease the solubility of most gases in a liquid. That why trout die in warm water, there is not enough oxygen in it. ( Explain in terms of gases dissolving and leaving solution )

3 Pressure only affects solutions in which the solute is a gas in liquid is most common, more pressure forces more gas into the solution That is what causes scuba divers to get the bends if they come up to fast. also big fish deep water?

More pressure on the top surface of the liquid causes more collisions on the top surface, which means more gas goes in than comes out.

Factors that affect the Rate of Solubility • Temperature • Surface area • Stirring • How and why? • demos

Expressing solution Concectration • Molarity • Molality • Percent by mass • Normality • Parts per million

Molarity = moles of solute liter of solution ( Demo use of volumetric flask and the difference between the two. ) Molality = moles of solute liters of solvent Pages 483 -484

Percent by mass = mass of solute X 100 mass of solution Or mass of solute / mass of solution times 100 Parts per million is the same as above except you multiply by 1, 000

Normality = gram equivalents liter of solution ( Explain what a gram equivalent is )

Colligative Properties of solution colligative properties are properties of a solvent that are affected by the presence of a solute. The properties are affected by the number of particles not their identity

We will talk about three colligative properties. Boiling point Freezing point Vapor pressure

The presence of salt in water, will raise the boiling point and lower the freezing point. It extends the liquid range in both directions before there is a phase change You may ask, how much ? For boiling - 1. 86°C per mole of solute per liter of solvent For freezing -. 51° C per mole of solute per liter of solvent

This is why we put salt on the roads and anti-freeze in our cars. How much do we need? There is math for that!

∆ T b = K bm ∆ (delta ) Tb is the change in boiling temp, Kb is the molal boiling point constant. 51 °C per mole/liter, and m is the molality of the solution.

∆ T f = K fm ∆ (delta ) Tf is the change in freezing temp, Kf is the molal freezing point constant 1. 86°C per mole/liter, and m is the molality of the solution. Every solvent has its own Kb and Kf value.

“That’s all folks”