1. Chapter 16 Homogeneous Mixtures Solutions & Colloids: Stuff Dissolved Together or evenly mixed Ex. (clear) Gatorade Heterogeneous Mixtures Suspensions Stuff Mixed together but they don’t dissolve evenly : Ex. Chocolate chip ice cream ()

2. Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred. EX. Chocolate in milk, OJ, Schuylkill water
Colloids: The particles are small in size between those of a suspension and those of a solution, they cloud the water and do NOT settle out.

3. Colloid? Suspension? or Solution?
Smog – A Gaseous Colloid

4. What is the main difference between solutions and colloids/suspensions?
DISSOLVING!
Solutions: when 2 or more substances dissolve together.
***Please note that this means one substance will seem to disappear between the others molecules.
Liquids!
Solids! (gold and nickel or copper and zinc)
Gases!

5. Solute Solvent Solutions have 2 parts:
A solute is the dissolved substance in a solution.(usually less) EX:
Sugar & Carbon dioxide
in soda drinks
Salt in salt water
Oxygen in air
Carbon in steel
Solvent
A solvent is the substance that does the dissolving in a solution. (usually more) EX:
Water in soda
Water in salt water
Nitrogen in air
Iron in steel

6. Well if the particles are small they both look like solutions %%$#@!!:
Which glass contains a colloid which a solution?
Use …
The Tyndall Effect:
When microscopic colloid particles scatter light, making a light beam visible. Solutions do not scatter light.
Which is which?
Liquids demo, Chalk demo if time
solution
colloid

7. Essential Vocabulary 1 . Super saturated Cool/add crystal
Solubility- is the maximum amount of substance that will dissolve at a specific temperature. The units for solubility are: grams of solute/100 grams solvent
Saturated solution- Contains the maximum amount of solute dissolved NaCl = 36.0 g/100 mL water
Unsaturated solution- Can still dissolve more solute (for example 28.0 grams of NaCl/100 mL)
Supersaturated- solution that is holding (or dissolving) more than it theoretically can; cooling it, and/or a “seed crystal” for nucleation will make it precipitate;
Super saturated
Cool/add crystal

8. Essential Vocab 2:
Gaseous solution: 2 or more gases dissolved together EX air or “Natural gas”
Solid solution: 2 or more solids dissolved together EX glass or “sea salt”.
***Liquid solution can be considered any solution where the solvent is a liquid gas+liquid, solid+liquid Liquid+liquid.
Alloy: A METAL and other solid dissolved together EX brass (copper/zinc)or stainless steel (iron/carbon/zinc)
Miscible/Soluble means that two liquids* can dissolve in each other EX. water and antifreeze (ethylene glycol)
Immiscible/insoluble liquids* can’t dissolve
oil and vinegar

9. Measuring Concentration :
a measure of the amount of solute dissolved in a given quantity of solvent
A concentrated solution has a large amount of solute
A dilute solution has a small amount of solute
These are qualitative descriptions
But, there are ways to express solution concentration quantitatively (NUMBERS!)

10. Concentrated vs. Dilute
These two solutions have .14 g of solute each…
DILUTE
Notice how dark the solutions appears.
Notice how light the solution appears.
Small amount of solute in a large amount of solvent.
Lots of solute, in a small amount of solvent.

11. Molarity: a unit of concentration
Molarity = moles of solute
liters of solution
Abbreviated with a capital M, such as 6.0 M
This is the most widely used concentration unit in chemistry.

12. Calculate Molarity Steps!
Recognize a concentration question. Asks about strength or weakness of a solution not dilutes one!
Convert grams to moles.
Convert mL to L
Divide mol /L then replace unit with M
*If you are given M then you need to rearrange the formula to solve for for L or mol
What is the molarity if you dissolve 35.1g of HCl into 325mL what is the molarity?
Molarity WS p6/7 then 8HW
35.1/ = mol /.325 = =2.96

13. Solvent VS Solute: ‘Like dissolves Like’
Not everything dissolves in everything! The simple guideline is: “Like Dissolves Like”
This means a non-polar solvent will only dissolve a non-polar solute.
Polar and ionic solutes usually dissolve best in polar solvents
Polar means the molecule has a “pole” or positive and negative end like a magnet. Nonpolar mean no poles.
Oil & alcohol demo
Some guidelines to seeing if it will dissolve
Organic compounds/hydrocarbons are often nonpolar due to carbon’s 4 bonds. Ex, methane, butane, most oils; HAVE SYMMETRY
Ionic compounds are VERY polar: salts, acids, water (even though it’s covalent H2O is NOT SYMMETRICAL)
When all else fails, draw the lewis structure,
then the molecular geometry, then dipole vectors!

14. Solvent VS Solute: ‘Like dissolves Like’
Example: Oils/oil paints (NP) dissolve in thinner (NP)
*Greases(NP) can be dissolved with most oils (NP) (oils to dissolve oils) Gasoline dissolves grease.
Example: Salts (P) dissolve in water (P)
Glucose C6H12O6 and water (P)?:
Soaps/detergents have both polar and non polar “ends” so they can dissolve oils AND in water!
Look at the shape!
POLAR
Like dissolves like WS
Polar and polar
BOTH!
Nonpolar and nonpolar
Nonpolar

15. Electricity and Electrolytes
Electricity is a flow of electrons.
Electrons ‘flow’ if they are free to transfer.
Ions in water and metals allow e- transfer. ?
An electrolyte is:
A substance whose (water) aqueous solution conducts an electric current. *this is what transmits your thoughts and movements!
Most Ionic compounds (aq) form electrolytes since they form ions and dissolve in water.
A nonelectrolyte is:
A substance whose aqueous solution does not conduct an electric current.
Most covalent compounds sugar, O2(aq).

16. Electrolytes vs. Nonelectrolytes
Ammeter: measures the flow of electrons (current)
through the circuit. (We used this in our ionic vs. covalent lab)
If the ammeter measures a current, bulb
glows then solution conducts and is an electrolyte.
If the ammeter fails to measure a current,
bulb does not glow, the solution is nonconducting and is a non-electrolyte.

17. Sugar solution (covalent) NaCl solution HCl acid solution
Try to classify the following substances as electrolytes or nonelectrolytes…
ELECTROLYTES:
NONELECTROLYTES:
Pure water
Tap water
Sugar solution (covalent)
NaCl solution
HCl acid solution
Lactic acid solution
Ethyl alcohol solution (covalent)
Pure NaCl crystals (not in water)
Matching then Page 2/3 Nature of solutions

18. Solubility Chart Reading
Solubility curves are used to show how the solubility of a substance changes with temperature.
The temperature of the solution affects how much of the solute is dissolved by the solvent.
Again, Increasing the temperature does not always increase the solubility.
Gases will decrease in solubility as temp increases.

19. How much KNO3 dissolves in 100g H2O at 50oC?
Find the line (red)
Find the temperature and follow up to the line. (green)
Read across to the y-axis and this is the answer. (blue)
60 g on your chart

20. Calculations using a Solubility Chart:
On the line solution of 40C is a saturated solution.
Below the line solution of 40C is unsaturated.
Calculate how much more can be dissolved, from the unsaturated solution of 90g:
Above the line solution of 40C is supersaturated.
Calculate how much extra has been dissolved in the supersat solution:
18g
12g

21. Making Solutions
In order to dissolve, the solvent molecules must come in contact with the solute.
1. Stirring (agitation) moves fresh solvent into contact with the solute.
2. Smaller pieces increases the amount of surface area of the solute.
- think of how fast candy or a mint dissolves after you chew it vs. before

22. Temperature and Solutions
3. Higher temperature makes the molecules of the solvent move faster and contact the solute harder and more often and Speeds up dissolving.
Higher Temperature ALSO Usually increases the amount that will dissolve;
*an exception is gases, which dissolve better in cold temps
Think about what happens when you open warm vs. cold soda

23. Dilution (weakening a solution)
Adding water to a solution will reduce the number of moles of solute per unit volume
but the overall number of moles remains the same!
Think of taking an aspirin with a small glass of water vs. a large glass of water
You still have one aspirin in your body, regardless of the amount of water you drank, but a larger amount of water makes it more diluted.

24. Dilution
The number of moles of solute in solution doesn’t change if you add more solvent so we can say:
The # moles before = the # moles after:
Formula for dilution: M1 x V1 = M2 x V2
M1 and V1 are the starting concentration and volume; M2 and V2 are the final concentration and volume.
THIS DOES NOT ALWAYS GIVE YOU THE “ANSWER!!”
INITIAL
FINAL

25. Dilution Example Ex dilution of a “koolaid” solution:
You have 1L of a 7.0M kool aid solution
You want to dilute it to make it ½ as strong. How much water do we need to add

26. Percent solutions can be expressed by a) volume or b) mass
Percent means parts per 100, so
Percent by volume: = Volume of solute x 100% Volume of solution
indicated %(v/v)
42 ml ethanol in 720ml of water?

27. Percent solutions Another way to do mass percentage is as mass/mass:
Percent by mass: = Mass of solute(g) x 100% Mass of solution(g)
Indicated %(m/m)
32 ml of ethanol is dissolved in 425 mL of water. What is the percent of the solution?
How many grams of salt are there in 52 mL of a 6.3 % solution?

28. Colligative Properties
-Properties of a solution that change based only on the number of dissolved particles
-Not on what kind of particle ions or molecules. Make no difference here.
-Three important colligative properties of solutions are:
Vapor pressure (evaporation) lowering
Boiling point elevation
Freezing point lowered

29. “Salts” in solution will IONIZE (or split), while others may not so they make more “pieces”
- Page 488
Colligative Properties
CaCl2 will have three particles in solution for each one particle it starts with.
Glucose will only have one particle in solution for each one particle it starts with C6H12O6.
NaCl will have two particles in solution for each one particle it starts with.

30. Vapor Pressure is LOWERED
Surface area is reduced, thus less evaporation, which is a surface property
The bonds between molecules keep molecules from escaping. So, in a solution, some of the solvent is busy keeping the solute dissolved.
This lowers the vapor pressure
Electrolytes form ions when they are dissolved, making more pieces.
NaCl ® Na+ + Cl- (this = 2 pieces)
More pieces = a bigger effect

31. Boiling Point is ELEVATED
The vapor pressure determines the boiling point. (Boiling is defined as when the vapor pressure of liquid = vapor pressure of the atmosphere).
Lower vapor pressure means you need a higher temperature to get it to equal atmospheric pressure
Salt water boils above 100ºC
The number of dissolved particles determines how much, as well as the solvent itself.

32. Freezing Point is LOWERED
Solids form when molecules make an orderly pattern called “crystals”
The solute molecules break up the orderly pattern.
Makes the freezing point lower.
Salt water freezes below 0ºC
Home-made ice cream with rock salt?
How much lower depends on the amount of solute dissolved.