1. Solutions Unit

2. Mixtures
A mixture is: a combination of 2+ pure substances (elements and/or compounds) that can be separated by PHYSICAL means.
Mixtures can be categorized into one of two groups:

3. Types of Mixtures
HETEROGENEOUS MIXTURE: mixture of 2 or more pure substances in different physical states; VARYING COMPOSITION (not uniform throughout)
Suspension: heterogeneous mixture that clearly separates
eventually separates upon standing
solid does not visibly dissolve in the liquid (or break down)
separate by filtration (using a filter)
relatively large particle size
Examples: sand in water , Italian dressing

4. Types of Mixtures (Continued)
Colloid: heterogeneous mixture that does not clearly separated
Cloudy (appear homeogenous, but are NOT)
do not settle (naturally; on their own) through time
can be separated by a centrifuge (forced gravity)
Medium to Small particle size
properties in between a suspension and a solution
Examples: Blood and Milk

5. Types of Mixtures (continued)
2. HOMOGENEOUS MIXTURE (AKA Solution): mixture of 2 or more pure substances in the Same Physical State;
CONSTANT COMPOSITION (uniform throughout)

6. Types of Mixtures (Continued)
Solutions
looks like clear, colored or colorless water
Extremely small particle size (you can’t see them)
may exist in any phase (liquid phase most common)
Examples: Saltwater, Kool-Aid, Club Soda

7. Types of Mixtures (Continued)
Alloy: solution where at least one of the materials is a metal (although most times it is a mixture of 2+ metals)
Metals arrange in an alternating pattern with a sea of mobile electrons gluing them together
Examples: Brass (zinc + copper), Steel (iron + carbon)
Now, we will focus on SOLUTIONS only…

8. Characteristics of Solutions
Homogeneous mixtures
Clear (as opposed to cloudy) and do not disperse light
Can have color or be colorless
Do not settle upon standing (after any amount of time)
Cannot be separated by filtration

9. Parts of a Solutions SOLUTIONS ARE MADE UP OF 2 PARTS:
SOLUTE: substance or substances that are dissolved in a solution (example: the salt in saltwater); solute is usually a solid and is the lesser quantity of the two (versus the solvent)
SOLVENT: the substance that is dissolving the solute (example: the water in salt water); solvent is usually a liquid and is the greater quantity of the two (versus the solute)

10. Solutions
AQUEOUS = a solution in which water is the solvent (aq) Example: NaCl (aq) is otherwise known as saltwater, is actually Na+ (aq) + Cl- (aq)

11. Solutions Metallic Alloy Ethyl Alcohol and Water
Table salt and water
Ethyl Alcohol and Water
CO2 and Water (club soda)
Air

12. Different Types of Solutions:
UNSATURATED: a soln in which more solute could be dissolved in a given volume of solvent
SATURATED: a soln containing the maximum amount of solute that will dissolve in a given volume of solvent
Saturated = solution equilibrium

13. Different Types of Solutions:
SUPERSATURATED: a soln that contains more solute than would normally dissolve in a given volume of solvent; usually requires an increase in temperature or pressure initially (VERY unstable)

14. Situation:
If you have an UNSATURATED solution and you add crystals, what will you observe? Crystals dissolve / disappear
The rate of dissolving is greater than the rate of precipitation
If you have a SUPERSATURATED solution and you add crystals, what will you observe? Crystals do not dissolve and more precipitate out
The rate of dissolving is less than the rate of precipitation
If you have a SATURATED solution and you add crystals, what will you observe? *crystals sink to the bottom 
The rate of dissolving is equal to the rate of precipitation

15. SOLUBILITY CURVES - USING TABLE G (of the Reference Tables):
HOW TO USE TABLE G:
Table G shows the number of grams of a substance that can be dissolved in 100 grams of H2O at temperatures between 1°C and 100°C. Each curve represents the maximum amount of a substance that can be dissolved at a given temperature. All lines that show an increase in solubility as temperature increases represent solids. The lines for gases slope downward.

16. ***If the intersection of GRAMS OF SOLUTE vs. TEMPERATURE falls:
On the curve, solution is Saturated
Under the curve, solution is unsaturated
Above the curve, solution is supersaturated
Try the Practice questions on the next page!!

17. Practice Table G Questions

18. SOLUBILITY FACTORS (Why do some things dissolve and others do not?)
Factor 1 – Nature of Solute & Solvent
Remember “Like Dissolves Like”
soluble
Insoluble
Insoluble
soluble
Insoluble
soluble

19. SOLUBILITY FACTORS (Why do some things dissolve and others do not?)
Factor 2 – Temperature
For solids, as Temperature increase, solubility Increases
Remember: Table G is there to help you!
Gases slope  solids slope.
For MOST gases, as temp. increases, solubility decreases
Example: heat soda  carbonation is LOST!(warm)

20. SOLUBILITY FACTORS (Why do some things dissolve and others do not?)
Factor 3 – Pressure
For solid or liquid solutes  No Effect
For gases dissolved in liquids  As pressure increases, Volume decreases, Solubility increases
Recall: We can change the volume of gases!
Reason: Gas is forced into less space per liquid, so it
DISSOLVES more!
Ex: can of soda
When packaged, soda is pressurized (so CO2 dissolves in the liquid). When you open the can, pressure is let out (pressure decreases in the can). So the gas particles are released and you get CARBONATION!

21. Solubility
*SOLUBILITY: a measure of how much SOLUTE will dissolve in a certain amt. of a given temp.
Soluble: Solute will dissolve; AKA miscible
*The more soluble something is, the more concentrated it can be in soln
Insoluble: solute will not dissolve
Concentration: Ratio of the amt. of solute per amount of solvent (solute/solvent)

22. Dilute vs. Concentrated
DILUTE: soln that has a relatively small amount of solute dissolved into a relatively large amount of solvent (weak solution)
(verb: to weaken the concentration of a soln)

23. Dilute vs. Concentrated
CONCENTRATED: Solution that has a relatively large amount of solute dissolved into a relatively small amount of solvent (strong solution)

24. Most vs. Least Concentrated (using table F)
Concentration is directly related to amt. of solute dissolved
Regents Question: Which solution is most/least concentrated?
Most concentrated = soluble compounds
Least concentrated = insoluble compounds
* If a compound doesn’t dissolve (insoluble) it doesn’t add to the concentration of the soln.

25. Rate of Solution (dissolving) Factors
Rate of soln = How Fast (speed) a solute dissolves
1. Size of the solute particles (surface area)
Increase surface or make particles smaller it will increase the rate at which your solute dissolves
The more surface area a solute has the more collisions it will have with the solvent and the faster it will dissolve
This can be done by crushing or grinding up the solute
Which dissolves faster sugar granules or sugar cubes?
*** Remember***
Large particles = small surface area
Small particles = large surface area
2. Agitation
Also knowing as stirring this will speed up dissolving because you will cause more solute and solvent collisions.
3. Temperature
for liquids and solids if you increase temperature the solute will dissolve faster
for gases it the opposite if you decrease the temperature the solute will dissolve faster

26. Concentration of Solution
The concentration of a solution is a measurement of the amount of solute dissolved in solution.
There are several ways of expressing the specific concentration of solute in a solution.
Percent by Mass
Percent by Volume
Parts per million
Molarity

27. Molarity Moles of Solute (mol) Liters of solution (L) Molarity (M) =
Molarity measures the concentration of a solution in terms of moles of solute in a given volume of solution.
The Molarity (M) of a solution is the number of moles of solute in 1L of solution.
When calculating the Molarity of a solution you may need to make conversions before you solve for and answer.
For example if you are given the mass of the solute you will need to convert to moles using the mole calculation equation on Table T.
You may also need to convert the volume of solution given if it is not in liters.
The units for molarity are mol./L or M for short
Moles of Solute (mol)
Liters of solution (L)
Molarity (M) =

28. Parts Per Million Mass of Solute Mass of Solution X 1,000,000
Parts per million (ppm) is similar to percent by mass because it compares masses. It represents the ratio between the mass of a solute and the total mass of a solution. Instead of multiply by 100 you multiply by 1,000,000.
ppm is often used to measure concentrations of solutes that are present in very small amounts. For example if you wanted to measure the concentration of chloride ions in tap water.
The units for parts per million are ppm
Mass of Solute
Mass of Solution
X 1,000,000
Parts Per Million =

29. Percent by Mass & Percent by Volume
Percent by mass is simply the mass of the solute divided by the total mass of the solution, expressed as a percentage (x100). Use a % sign as the unit.
Percent by volume is simply the volume of the solute divided by the total volume of the solution, expressed as a percentage (x100). Use a % sign as the unit.
Mass of Part (solute)
Mass of Whole (solution)
Percent by mass =
X 100
Volume of part (solute)
Volume of whole (solution)
Percent by volume =
X 100

30. Helpful Hint about Concentration Problems.
Remember that a solution is made up of the solute and solvent combined.
So if you are performing a concentration problem you may need to add the masses or volumes of your “solute” and “solvent” to solve for the mass or volume of the “solution”, which is what you need for all concentration equations.
If you are given the mass or volume of the “solution” then you do not need to worry about adding the solute and the solvent.
Solution = Solute + Solvent

31. Calculating [Concentration] - all these formulas can be found on Table T! Use the following methods/formulas to calculate the concentrations of the solutions below. SHOW YOUR WORK.

32. Work on Practice Problems !!!

33. Colligative Properties
Some properties (like boiling point and melting point) of substances change when non-volatile substances are added.
COLLIGATIVE PROPERTIES FOR ELECTROLYTES
(Based on the number of particles)
Electrolyte = A substance that produces ions when dissolved in a solution. Because the ions are FREE TO MOVE AROUND (mobile) in the solution, the solution is able to conduct electricity (salts).
Non-electrolytes = A substance that produces molecules when dissolved in solution. They do not break up into ions (i.e. sugar)
When a solute is dissolved in a solvent, solvent molecules surround the particles of the solute. This causes the boiling point and freezing point of the solution to change in a very specific and predictable way.

34. Boiling Point Elevation
= BP increases when a solute is dissolved.
Ex: Adding salt to water allows you to boil pasta at oC (cooks faster)

35. Freezing Point Depression
= FP decreases when a solute is dissolved
Example: Putting salt on roads causes ice to melt because it drops the FP below 0oC

36. IONIC VS MOLECULAR SOLUTES:
IONIC VS MOLECULAR SOLUTES: * Why do we salt the roads in the winter rather than sugar them?!?!?

37. Freezing Point Depressions comparison
NaCl CaCl2
-21oC oC
*CaCl2 i$ even better than NaCl, $o why don’t we u$e it to $alt our road$?
Becau$e __________________________

38. Compare the following:
Which will have the lowest freezing point?
Which will have the highest freezing point?
1 mole of MgCl2 in 500 g water
1 mole of C6H12O6 in 500 g water
Freezing point will always be lower than 0°C.

39. Compare the following:
Which will have the highest boiling point?
Which will have the lowest boiling point?
1 mole of MgCl2 in 500 g water
1 mole of C6H12O6 in 500 g water
Boiling point will always be higher than 100°C.