1. Chapter 8 Solutions

2. Solutions and Other Mixtures
Heterogeneous Mixtures: Does not have a fixed composition (Particles not distributed evenly)
Suspensions: particles are large and settle out
Pulp in orange juice
Particles may be filtered out

3. Solutions and Other Mixtures
Some mixtures of two liquids will separate
Oil, vinegar, and flavoring can be shaken together to make salad dressing. But the dressing is a heterogeneous mixture.
When the dressing stands for a few minutes, two layers form.
The two liquids separate because they are immiscible, which means they do not mix
Oil floats to the top since it is less dense
The process of pouring a less dense liquid off a denser liquid is called decanting

4. Solutions and Other Mixtures

5. Solutions and Other Mixtures

6. Solutions and Other Mixtures
Colloid: particles are too small to settle out
The color in Latex paint comes from solid particles of colored pigments that are dispersed in water
Particles small enough to pass through filter
Even though particles are small they still scatter light that passes through he colloid (Tyndall effect)

7. Solutions and Other Mixtures

8. Solutions and Other Mixtures
Other colloids:
Dispensing gas in a liquid
Whipped cream
Dispensing gas in a solid
Marshmallows
Dispensing of water droplets in air
Fog
Dispensing of small particles in air
smoke

9. Solutions and Other Mixtures
Some immiscible liquids can form colloids
Mayonnaise is a colloid made up of tiny droplets of oil suspended in vinegar
Egg yolk coats the oil droplets so that they do not join together and form a separate layer
Cream is a mixture of oil, proteins, and carbohydrate dispersed in water. The lipid is coated with protein that acts as an emulsifier therefore spread throughout the mixture
Emulsion: colloid in which liquids that usually do not mix are spread throughout each other
One liquid is dispersed in the other

10. Solutions and Other Mixtures

11. Solutions and Other Mixtures

12. Solutions and Other Mixtures
Homogeneous mixtures: look uniform because the individual components of the mixture are too small to be seen
Are solutions: all homogeneous mixtures are also solutions
Solute: substance that dissolves
Solvent: substance in which the solute dissolves
Example: salt water

13. Solutions and Other Mixtures
Two or more liquids that form a single layer when mixed are miscible (one liquid is water)
Alcohol
Beer
Drinking alcohol

14. Solutions and Other Mixtures
Liquid solutions that do not contain water
Nail polish remover
Crude oil
Distillation: process that separates miscible liquids

15. Solutions and Other Mixtures

16. Solutions and Other Mixtures

17. Solutions and Other Mixtures
Alloys: homogeneous mixture that is usually composed of two or more metals (solids can dissolve in other solids)
Metals melted to a liquid and mixed
Have properties that the individual metals do not
Brass: solution of zinc dissolved in copper metal
Bronze: solution of tin in copper metal
Steel: metal solution that contains some non-metals (carbon)

18. How Substances Dissolve

19. Water
Is V-shaped
Two hydrogen atoms are located at the same end of the molecule, and oxygen is at the opposite end
This arrangement allows oxygen to pull the shared electrons toward itself and away from the two hydrogen atoms
The electron pairs are NOT shared equally, but spend more time in the vicinity of oxygen
Because electrons are negatively charged, the oxygen end of the molecule is slightly more negative and the hydrogen end slightly more positive
Because water has two poles of charge, it is a polar molecule, or dipole

20. COVALENT BONDS

21. Polar and Nonpolar Molecules
Polar molecules orient themselves toward other dipoles or toward charged particles (such as ions and some proteins), and they play essential roles in chemical reactions in body cells

22. Polar and Nonpolar Molecules
Different molecules exhibit different degrees of polarity, and we can see a gradual change from ionic to nonpolar covalent bonding
Extremes:
Ionic bonds: complete electron transfer
Nonpolar covalent bonds: equal electron sharing
There are various degrees of unequal sharing in between

23. IONIC/POLAR/NONPOLAR

24. Hydrogen Bonds
Weak attractions that form between partially charged atoms found in polar molecules
Hydrogen bonds form when a hydrogen atom, already covalently linked to one electronegative atom (usually nitrogen or oxygen), is attracted by another electron-hungry atom, and forms a bridge between them
Common between dipoles such as water molecules, because the slightly negative oxygen atoms of one molecule attract the slightly positive hydrogens of the other molecules

25. HYDROGEN BOND

26. Hydrogen Bonds
Surface tension is due to hydrogen bonds between water molecules
Although hydrogen bonds are too weak to bind atoms together to form molecules, they are important as Intramolecular bonds, which bind different parts of a single large molecule together into a specific three-dimensional shape
Some large biological molecules, such as proteins and DNA, have numerous hydrogen bonds that help maintain and stabilize their structures

27. How Substances Dissolve
Like dissolves like: means that a solvent will dissolve substances that have molecular structures that are like the solvent’s structure
Polar dissolve polar
Many substance dissolve in water (universal solvent)
+/- charges attract charges of solute
Nonpolar dissolves nonpolar
Nonpolar substances usually do not dissolve in water
Nonpolar molecules do not have partially negative and positively parts because the electrons are distributed evenly over the whole molecule
Nonpolar solvents must be used to dissolve nonpolar materials
Oil based paint must be dissolved by nonpolar solvent

28. How Substances Dissolve

29. How Substances Dissolve
The dissolving process:
Kinetic theory of matter states that molecules are always moving
The energy transferred from the solvent to the solute, as well as the attractive forces between the solvent and solute molecules, causes molecules at the surface of the substance to dissolve

30. How Substances Dissolve
The dissolving process:
Solutes with a larger surface area dissolve faster
Small pieces of a solid dissolve faster than large pieces of the same solid (small pieces have a larger surface area)
Cube of 1 cm on each edge
Each face has an area of 1 cm2
6 surfaces= total surface area of 6 cm2
Large Cube broken down to smaller cubes of 0.1 cm on each edge
Each face has an area of cm2
6 surfaces= total surface area of cm2
Total surface of 1,000 cubes is 1,000 x 0.06cm2 = 60 cm2
Which is 10 times the surface area of the larger cube

31. How Substances Dissolve
Surface area to volume ratio
SA/Vol

32. How Substances Dissolve

33. How Substances Dissolve
The dissolving process:
Stirring or shaking helps solids dissolve faster
Solids dissolve faster when the solvent is hot

34. How Substances Dissolve
Solutes affect the physical properties of a solution
Boiling point of water is 1000C and the freezing point is 00C
If you add salt (NaCl) the boiling point will increase and the freezing point will decrease
Cooking and melting winter ice
Ethylene glycol (antifreeze) in car
Raising boiling point and lowers freezing point

35. Solubility and Concentration
Solubility of a substance is the maximum mass of a solute that can dissolve in 100 g of solvent at a certain temperature and standard atmosphere pressure
Different substances have different solubilities in water
Depends on the on the strength of the forces acting between the solute particles and the strength of the forces acting between water molecules and solute particles

36. Solubility and Concentration

37. Solubility and Concentration
How much of a substance is in a solution?
Concentration: the amount of a particular substance in a given quantity of a mixture, solution, or ore:
Not quantitative terms:
Concentrated: large amount of solute
Dilute: small amount of solute
Saturated: dissolved solute is in equilibrium with undissolved solute. So, if you add more solute, it just settles to the bottom of the container
Heating can dissolve more solute (supersaturated)
Unsaturated: least than the maximum amount of solute

38. Solubility and Concentration
Temperature and pressure affect the solubility of gases
Temperature:
Unlike solids, gases are less soluble in warmer water
Fish???
Pressure:
High: more gas dissolves
Low: less gas dissolves
Example:
Carbonated drink
Scuba diver (bends)

39. Solubility and Concentration
Concentration of solutions
Terms concentrated, dilute, saturated, and unsaturated do not reveal the quantity of dissolved solute
One of the most common ways of expressing the concentration of a solution is molarity
Molarity is expressed as moles of solute per liter of solution

40. Solubility and Concentration
Molarity = moles of solute/liters of solution
M = mol/L
Example: a 1.0 M is read as one molar solution
A 1.0 M solution of NaCl contains 1.0 mol of dissolved NaCl in every 1.0 L of solution

41. Solubility and Concentration
Calculate the molarity of sucrose, C12H22O11, in a solution of 124 g of solute in L of solution
Moles C12H22O11 = mass C12H22O11/molar mass C12H22O11
Molarity = moles C12H22O11 / liters of solution
Molar mass C12H22O11= 342 g
Moles C12H22O11= 124 g / 342g/mol = 124g x 1mol/342g = mol
Molarity of solution=0.362 molC12H22O1 1 / L solution=0.724 M