SOLUTI

ONS

SOLUTIONS

• Type of homogenous mixture

• Has the same composition, color and density throughout

• Composed of:

Solute – substance that is being dissolved

Solvent- substance that is doing the dissolving

• Most common solution – solid in liquid

• Solutions can also occur between:

solid- solid

gas - liquid

SOLID IN LIQUID SOLUTIONS

Solute- solid

Solvent – liquid

usually water- universal solvent

Examples: fruit drinks

sports drinks

Dissolution occurs are the surface of the solid

1) water molecules (polar) surround the solid molecules with their

negative ends attracted to the positive ends of the solid

2) water molecules then pull the solid into solution

3) solid molecule and water molecules mix evenly

OTHER SOLUTIONS

Gas-Gas Solutions

ex: air

Liquid – liquid Solutions

Ex: lemonade; mango juice

liquids are more freely moving and thus can mix together

Solid-Solid Solutions (alloys)

Ex: Bronze ( Copper and tin)

Sterling Silver

Brass

Solids must first be melted and then mixed together because of the crystalline shape of solids

RATE OF DISSOLVING

Techniques to speed up the rate of dissolution

1) Stirring – this brings more fresh solvent into contact with solute

polarity of both solute and solvent makes solute dissolve faster

2) Crystal size- make large crystals smaller

this makes the surface area larger—because dissolution occurs at surface area of the solid increasing surface area allows more solvent to come into contact with solute

3) Temperature- increasing temperature increases molecular movement of solvent

Controlling the Process- Combination of two of the above techniques increases dissolution even more

SOLUBILITY

• Maximum amount of a solute that can be dissolved in a given amount of solvent at a given temperature

• Concentrated solutions- large amount of solute is dissolved in the solvent

• Diluted solutions - small amount of solute is dissolved in the solvent

• Solubility of common substance in 100 g of water at 20°C:

salt 35.9

baking soda 9.6

sugar 203.9

hydrogen 0.00017

carbon dioxide 0.16

TYPES OF SOLUTIONS

Saturated Solutions:

Solution that contains all the solute a solvent can hold at a given temperature

Unsaturated Solutions:

Solution that dissolve more solute at a given temperature

Supersaturated Solutions:

Solution that contains more solute than a saturated solution

This solution is very unstable---- energy is given off

SOLUBILITY CURVE

Rule of Thumb for reading the solubility curve:

Unsaturated – below the curveSaturated - is the curveSupersaturated – above the curve

SOLUBILITY OF GASES

Increasing Solubility:

1) Pressure - Increasing pressure increases the amount of gas

dissolved in liquids

reason why soda fizzes when popped

2) Temperature - cooling the solvent increases the amount of gas

that dissolves

reason why soda gets warm when top is popped- more CO2

has escaped

PARTICLES IN SOLUTION

Electrolytes – compounds that produce solutions of ions that conduct

electricity

Ex: NaCl – stong electrolyte

conducts strong current

exist completely as ions in solutions

Acetic Acid – weak electrolyte

conducts weak current

exist as molecules in solutions

Nonelectrolytes – compounds that do not produce solutions of ions

Ex: sucrose and ethyl alcohol

PARTICLES IN SOLUTION

Two Ways to produce ionic compounds

1) Ionization – production of charged particles (ions)

ex: HCl

2) Dissociation – separation of positive and negative particles from ionic

crystals

ex: NaCl

-- NaCl crystals will break apart under the influence of water

-- Na and Cl pull apart (dissociate) and move freely in solution

-- Na and Cl ions can now produce an electric current

SOLUTE EFFECT ON SOLVENT

• Lowers the freezing point of the solvent

- solute interferes with the formation of particle arrangement

ex: antifreeze

• Raises the boiling point of the solvent

- solute interferes with the evaporation of solvent particles

- more energy is needed for solvent particles to change phase from

liquid to gas

ex: car radiators

NONPOLAR SOLUTES• Many solutes do not dissolve in water

- there is no distinct dissociation of ions

Ex: Vinegar and Oil

• Polar and Nonpolar Solutes

- polar end dissolves polar molecules; nonpolar end dissolves nonpolar molecules

Ex: Ethanol

- dissolves iodine (nonpolar0

- dissolves water (polar)

Useful Nonpolar Molecules: Disadvantages of Nonpolar Molecules:

Mineral Oil 1) flammable

turpentine 2) toxic

dry cleaner solutions

SOAPS

• Salts of fatty acids

• Hydrocarbons with carboxyl end (-COOH)

• Contain both polar and nonpolar properties

The making of soaps:

H of the acid group is removed leaving a negative charge

K or Na ion left with positive charge

• The ionic nature of the acid dissolves in water

• The hydrocarbon end dissolves in oils

VITAMINS

Vitamin A – nonpolar molecule that dissolves in fats

Vitamin B – polar molecule that dissolves in water

Vitamin C – polar molecule that dissolves in water

Nonpolar molecules can accumulate in the body and become toxic

Polar molecules do not accumulate in the body—excess is removed in urine