solutions. type of homogenous mixture has the same composition, color and density throughout...
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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
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