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Solutions. CPS Chemistry. Definitions. Solutions A homogeneous mixture of two or more substances in a single phase Soluble Capable of being dissolved. Solvent Dissolving medium in a solution What is doing the dissolving Solute Substance dissolved in a solution What is dissolved - PowerPoint PPT Presentation
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SolutionsCPS Chemistry
Definitions Solutions
A homogeneous mixture of two or more substances in a single phase
Soluble Capable of being dissolved
Solvent Dissolving medium in a solution
What is doing the dissolving Solute
Substance dissolved in a solution What is dissolved
Example Sugar in tea –
tea is solvent, sugar solute
Types of Solutions
May exist as gasses, liquids or solids One component is designated as
solvent and one as solute Chart on pg. 396
Phase If there are two different types of
substances it is a phase change Water + salt; water and gas
Same phase Water and apple juice
This is an aqueous solution Means there is water involved
Alcohol and liquid Tincture solution Means there is alcohol involved
Mixtures 2 or more substances when each
retains its properties Homogeneous
Uniform distribution of particles 0.01-1nm size particles, can be atoms Can be physically separated Ex. Salt water, air Also called solution
Heterogeneous Distribution of particles is not uniform
Can be separated by physical means
Particle size 1-1000 nm (nanometer)
Suspensions When particles in a solvent are so
large that they settle out unless stirred constantly
Gravity pulls particles to bottom of container
Particles >1000nm in diameter, 1000 times as large as atoms
Ex. Italian salad dressing, muddy water
Can be separated by passing liquid through a filter
Colloids Has particles that are intermediate in
size and they remain dispersed in the solute
1-1000nm particle size Emulsion or foam are specific types Mayonnaise is an emulsion of egg and
oil
The Tyndall effect Is a sign that it may be a colloid The particles are not large enough to
be seen, but large enough to scatter light
Ex: headlights on a foggy night
Test tube
Light Beam
Test tube
Light Beam
Tyndall Effect, beam of light can be seen in suspensions and colloids
No Tyndall Effect, beam of light cannot be seen in solutions
Electrolytes vs. Nonelectrolytes Electrolyte
A substance that dissolves in water to give a solution the ability to conduct electricity
Nonelectrolyte A substance that when dissolved in water
to make a solution that does not conduct electricity
When ionic compounds dissolve, the positive and negative ions separate from each other and are surrounded by water molecules
When the ions are free to move, electricity moves easily
How to Make Solutions You need to know the:
Solubility –the maximum amount solute can dissolve in a solvent
Rate – how fast the solute dissolves
Factors that affect rate of dissolution Surface area of the solute
The larger the surface area, the more quickly it dissolves
Agitation of a solution When you stir or shake the solute
particles are dispersed throughout the solvent, and it increase the rate of dissolution
Saturated Solutions A solution that contains the maximum
amount of dissolved solute is saturated
The factors that determine saturation are mass of solvent, mass of solute and the temperature
When a solution contains less than the maximum saturation it is considered unsaturated
Supersaturate A solution that contains more
dissolved solute than a saturated solution contains under the same conditions
But will form crystals when disturbed or cooled
Like dissolves like The rule for predicting whether one
substance will dissolve in another is related to the type of bonding, the polarity of a molecule and the intermolecular forces between the solute and solvent
Things need to be similar for them to dissolve
Solvent Solute = Solution
Polar Polar = yesPolar non-polar= noNonpolar Polar = noNonpolar Nonpolar = yes
Reminder molecule polarity
More Vocab. Immiscible
Liquid solutes and solvents that are not soluble in each other Oil and water Oil and salt
Miscible Liquids that dissolve freely in one
another in any proportion Water and food coloring
Back to Temperature- Solubility Increase temp =increase KE=
increase in solubility + increase in rate Higher temps dissolve faster( Liquids)
BUT Gasses act differently
Increase temp = decrease solubility Because gasses will leave solution at high
temps
Pressure –solubility There is no difference to solids or
liquids, but with an increase in pressure it will increase the solubility of a gas For example CO2 dissolved in a solution
of sucrose and water (soda) will come out of solution when the pressure is decreased (opening the bottle, lets the soda bubble)
Size of the Particle – rate Because the dissolution occurs only at
the surface of the solute, when you crush a substance,
You get a larger surface, so you increase the rate at which it is dissolved
Stirring - rate When you agitate the solvent, you
increase the contact with the surface of the solute
You increase the rate
Amount of Solute -rate As you increase the amount of solute
you want to dissolve You decrease the solubility and rate
Concentration A measure of the amount of solute in
a given amount of solvent or soulution
MATH IS INVOLVED
Molarity The number of moles of solute in one
liter of solution Molar mass- as a reminder it is the
mass listed on the PTE.. If it is for a compound, you simly add the masses of the atoms of the emperical formula
Ex. H2O H=1.00 O=15.99 total molar mass is 1.00+1.00+15.99 =17.99g
Formula
Amount of solute (mol)Molarity ( M) = ______________________
Volume of solution (L)
Practice You have3.50 L of solution that
contains 90.0 g of sodium chloride, NaCl. What is the molarity of that soulution?
Mass of solute 90.0 Solution volume = 3.50 L Molar Mass if NaCl 58.44 g/mol
Molality Don’t confuse them… The concentration of a solution
expressed in moles of solute per kilogram of solvent
You measure the mass of the solvent…
Formulamoles of solute (mol)
Molality = ______________________ mass of solvent (Kg)
Practice A solution was prepared by dissolving
17.1 g of sucrose C12H22O11 in 125g of water. Find the molal concentration
Given Solute mass = 17.1g sucrose Solvent mass = 125 g H2O
Colligative Properties Boiling- point elevation Freezing-point depression Vapor-pressure lowering Osmotic pressure
These change in relation to the total number of solute particles present
They are a constant that can be used to calculate the changes in solvents that contain nonvolatile solutes
Electrolytes have greater affects on colligative properties