1. Chapter 7- Solutions and Other Mixtures

2. Mixtures Variable combination of 2 or more pure substances.
Heterogeneous
Homogeneous (solutions)

3. Heterogeneous Mixtures
Composed of dissimilar components; not uniform structure or composition throughout
Examples: Fruit salad, orange juice,
Types of Heterogeneous Mixtures
Suspensions
Colloids
Emulsions

4. Suspension heterogeneous large particles
The particles are more or less evenly dispersed throughout a liquid
particles settle when mixture is allowed to stand
EX: fresh-squeezed lemonade, italian salad dressing, things that say shake well before using!

5. Suspension made of two liquids
Example- oil and vinegar
Two layers separate because liquids are immiscible
The heavier (more dense) liquid settles to bottom
The lighter liquid can be decanted (poured) off

6. Colloid Heterogeneous medium-sized particles particles don’t settle
EX: milk, whipped cream, egg whites,

7. Colloids and the Tyndall Effect
Because the particles in colloids are so small, they pass through ordinary filters and stay dispersed throughout the mixture
The particles ARE large enough to scatter light
This scattering of light is called the Tyndall Effect
Mixture on right is a colloid

8. Emulsions
A colloid in which two or more immiscible liquids in which one liquid is dispersed in the other
Example: Mayonnaise
Small droplets of oil suspended in vinegar

9. Heterogeneous Mixtures
Examples:
mayonnaise
muddy water
fog
marshmallows
Italian salad dressing
Colloid/emulsion
suspension
colloid

10. Homogeneous Mixtures
Also called Solutions because they have a uniform composition
Plain water is homogeneous because it is a single substance
Saltwater is also homogeneous because it is a uniform mixture of water molecules, sodium ions, and chloride ions

11. Solutions
Solutions are a homogeneous mixture made up of tiny particles that do not settle.
Solutions are made up of different substances that are dissolved.
Ex: Kool-Aid, Tea, Sprite
Miscible liquids mix to form solutions
Ex: Sprite, rubbing alcohol
Can be separated by distillation (based on different boiling points)

12. There are two parts of a solution:
Solutions
There are two parts of a solution:
Solute
Solvent

13. Solute In a solution, the solute is the substance that is dissolved.
For example, in Kool-Aid, the solute would be the sugar.

14. Solvents
In a solution, the substance that does the dissolving is the solvent.
In Kool-Aid, the solvent is the water.

15. Solutes and Solvents
Solutes are not always solid, and solvents are not always liquid.
Fuels like gasoline are solutions of petroleum
Other states of matter can form solutions
Ex: the air you breathe is a mixture of oxygen, nitrogen, argon, and other gases
Two solids can be dissolved together to make a solution called an alloy.
Ex: Bronze is a solution of tin and copper like in a trumpet

16. Solutes and Solvents Furthermore, two gases can be dissolved together.
Ex: Carbon dioxide is a solution of oxygen and carbon

17. Examples
In the following examples, tell which substance is the solute, and which is the solvent:
Tea
Carbonated Water
Salt Water

18. How Substances Dissolve

19. Water: The Universal Solvent
Liquid you drink are mostly water
Your body is 75% water
The earth is 67% water
Many things can dissolve in water, and for this reason it is called the Universal solvent

20. Polarity of Water
Remember from chapter 5, a polar molecule has unequal sharing of electrons
Water is a polar molecule
Polar molecules have a positively and negatively charged sides
Water can dissolve ionic compounds because it can attract the positive and negative ions of ionic compounds

21. Polarity of Molecules
This attraction between water molecules and ionic compounds results in the ions pulling away from the crystal
In NaCl, the sodium ions are attracted to the negative oxygen atoms of the water molecules and the chlorine ions are attracted to the positive hydrogen atoms of the water molecules
Eventually, all ions in the NaCl crystal are pulled into solution and completely dissolved

22. Ionic Compounds and Water
Not all ionic compounds dissolve in water
To dissolve an ionic substance:
Water molecules must exert a force on the ions that is more attractive than the force between ions in the crystal
This applies to all solvent and solute molecules (solvent molecules must exert more force on the particles of the substance than the particles exert on each other

23. Hydrogen Bonding in Water

24. Hydrogen Bonding in Water
Hydrogen bonding pulls water molecules close together
The following properties of water can be attributed to hydrogen bonding:
Low molecular mass
Fairly dense
High boiling point
Polar molecules dissolve polar molecules
In ethanol, the –OH group makes it polar, the positive hydrogen atom of a water molecule attracts the negative oxygen atom of an ethanol molecule

25. Hydrogen Bonding Animation
See how ionic bonds are dissolved in water

26. What if it’s not polar?
Remember polar molecules dissolve polar molecules
Non-polar molecules dissolve non-polar molecules
Non-polar compounds’ electrons are distributed equally among the atoms

27. “Like Dissolves Like”
NONPOLAR
POLAR

28. Factors Affecting Dissolving
Stirring or shaking a solution helps the solute dissolve faster
Stirring moves dissolved solute molecules away from undissolved solute, and more solvent can reach the undissolved solute
Solutes with a larger surface area dissolve faster
Smaller pieces dissolve faster than larger pieces
Solutes dissolve faster when the solvent is hot
KMT-particles are moving faster solvent molecules collide more with solute molecules

29. Solutes effect the physical properties of solutions
Solutes can lower the freezing point of a solution and raise its boiling point
Ex: salting the road in the winter

30. Solubility and Concentration

31. Solubility Insoluble: solute not able to be dissolved (oil and water)
Soluble: solute able to be dissolve (sugar and water)
Solubility: The maximum amount of a solute that can dissolve in a given quantity of solvent at a given temperature and pressure
Why you can’t dissolve all of a solute

32. Solubility
Different substances have different solubilities; see Table 1 page 240
The solubility of Silver Nitrate (216 g/100 g of water)is greater in water than Calcium Chloride (75 g/100 g of water)
Solubility depends on the strength of forces acting between the water and solute molecules compared to forces between the solute molecules

33. Concentration Weak solution: only a small amount dissolves in solvent
Strong solution: a large amount dissolves in solvent
These don’t specify concentration
The amount of a particular substance in a given quantity of a mixture, solution, or ore
Concentrated solution: contains a large amount of solute
Dilute solution: contains a small amount of solute

34. Saturation
In a solution, there’s only so much solute that a solvent can dissolve.
When a solvent can no longer dissolve any solute, it is saturated.

35. Saturation
Saturation is the point at which no more solute can be dissolved.
Ex: Adding sugar to tea
Solutions can be:
Unsaturated
Saturated
Supersaturated

36. Unsaturated Solutions
Unsaturated solutions are capable of dissolving more solute.
Ex: Adding sugar to hot tea. All the sugar is dissolved, the tea is unsaturated.

37. Saturated Solutions
Saturated solutions can not dissolve any more solute.
Ex: You add more sugar to your hot tea. Grains of sugar sink to the bottom and are not dissolved.

38. Supersaturated Solutions
Supersaturated solutions have dissolved more solute than is normal.
Usually, supersaturation occurs if the temperature of the solution has been altered.
Ex: Reheating your tea, then adding more sugar.

39. substance being dissolved
Molarity
Concentration of a solution.
substance being dissolved
total combined volume

40. Molarity
2M HCl
What does this mean?

41. Molarity Calculations
molar mass
(g/mol)
6.02  1023
(particles/mol)
MASS IN
GRAMS
MOLES
NUMBER OF
PARTICLES
LITERS
SOLUTION
Molarity
(mol/L)

42. Molarity Calculations
How many grams of NaCl are required to make 0.500L of 0.25M NaCl?
0.500 L
0.25 mol
1 L
58.44 g
1 mol
= 7.3 g NaCl

43. Molarity Calculations
Find the molarity of a L solution containing 10.0 g of NaF.
10.0 g
1 mol
41.99 g
= mol NaF
0.238 mol
0.25 L
M =
= 0.95M NaF

44. Other measures of concentration
Mass percent: like in the drugstore, can find 3% hydrogen peroxide
ppm: parts per million
ppb: parts per billion
ppm and ppb are used for solutions that contain very small amounts of solute
USEPA set level of lead in drinking water at 15 ppb

45. Triangle to Solve Equations
moles L M