1. Solutions, Acids & Bases
Physical Science: Concepts in Action
Chapter 8
Solutions, Acids & Bases

2. 8.1 Formation of Solutions
Objectives:
1. Describe how a substance can dissolve in water by dissociation, dispersion or ionization
2. Describe how physical properties of a solution can differ from those of its solute and solvent
3. Identify energy changes that occur during formation of a solution
4. Describe factors affecting the rate at which a solute dissolves in a solvent

3. Dissolving: Dissociation, Dispersion or Ionization
Substances can dissolve in water by three ways:
1. dissociation
2. dispersion
3. ionization
Definition: dissociation is the process by which an ionic compound separates into ions
Ex: NaCl

4. Phet Salts & Solubility

5. Definition: dispersion is the process by which a covalent compound breaks into small pieces that spread throughout the water
Ex: sugar dissolves in water
Definition: ionization is the process by which neutral molecules (acids or bases) gain or lose electrons (forming ions)
Ex: hydrogen chloride gas & water react to form hydronium ion (H3O+) and chlorine ion (Cl-)

6. Physical Properties: Solute & Solvent
Definition: a solute is a substance whose particles are dissolved in a solution (often a solid)
Definition: a solvent is the substance in which the solute dissolves (often a liquid)
Solutes and solvents can take the form of solids, liquids or gases
The solution takes the state of the solvent

7. Three physical properties of a solution that can differ from those of its solute and solvent are conductivity, freezing point & boiling point
Definition: conductivity is the ability of a solution to conduct electricity
Ex: NaCl is a poor conductor until it is placed in water & dissociates

8. Phet Sugar and salt solutions (conductivity）

9. Definition: the freezing point is the temperature at which a liquid becomes a solid
Freezing point is changed with the addition of ionic compounds like MgCl2 or other ionic compounds
The freezing point is lowered when ionic compounds are added

10. Definition: the boiling point is the temperature a liquid substance becomes a gas
Coolants used in radiators (ethylene glycol, a molecular substance) raise the boiling point of water & keeps the engine from overheating
Formation of new solutions by the addition of ionic or molecular compounds requires an energy change

11. Ted-ed Under the hood: The chemistry of cars - Cynthia Chubbuck

12. Energy Changes & Solution Formation
During formation of a solution, energy is either released or absorbed (Hot vs. Cold Packs)
The process is endothermic or exothermic
Forming attractions releases energy (exothermic)
Breaking attractions requires or absorbs energy (endothermic)

13. Demo Exo vs Endo heats of Solution 1g Kcl in 5mL H2O
5mL alcohol (or 1g NaOH) in 5mL H2O

14. Factors that Affect Dissolving Rate
Factors that affect the rate of dissolving include surface area, stirring and temperature
Dissolving takes place at the surface
The greater the surface area, the faster the dissolving
Stirring or shaking makes a substance dissolve faster by increasing the surface area exposed to the solvent

15. 8.2 Solubility and Concentration
Objectives:
1. Define solubility and describe factors affecting solubility
2. Classify solutions as unsaturated, saturated or supersaturated

16. Solubility & Factors Affecting Solubility
Definition: solubility is the maximum amount of a solute that dissolves in a given amount of solvent at a constant temperature
Solutions are classified as saturated, unsaturated or supersaturated
The classification depends on the amount of solute in solution

17. 3 types of solutions
Definition: a saturated solution is one that contains as much solute as the solvent can hold at a given temperature
Definition: an unsaturated solution has less than the amount of solute that can be dissolved
Definition: a supersaturated solution contains more solute than the solution can normally hold at a given temperature

18. Unsaturated vs. Sat.

19. Sodium Acetate

20. Vids Supersaturated solution- hot ice
Rock candy crystallization

21. Factors affecting solubility
Polar and Nonpolar solvents
“Like dissolves like”
Temperature
Inc. in solubility for solids, dec. for gases
Pressure
Inc. in pressure forces gas bubbles to dissolve

22. Polar and Nonpolar solvents
“Like dissolves like”
Polar solvents dissolve polar solutes

23. Temperature
Inc. in solubility for solids, dec. for gases

24. Pressure
Inc. in pressure forces gas bubbles to dissolve

25. Concentration of Solutions
Percent by volume
Liquid in liquid / gas in gas
Percent by mass
Solid in liquid
Molarity
Used for chemical reactions

26. Percent by volume

27. Percent by mass

28. Molarity 1 molar solution Molar Mass NaCl = 58.44 g
Molar Mass Sugar c12H22O11 = 342 g

29. A natural indicator Indicator – blueberry juice Acids and bases –
Acids are sour and reacts with metal; bases are bitter and slippery
Lemon juice, Vinegar, Window cleaner, Baking soda

30. 8.3 Properties of Acids and Bases
Objectives:
1. Define acid and describe the general properties of an acid
2. Define base and describe some of the general properties of a base

31. Acids
Definition: an acid is a compound that produces hydronium ions (H3O+) when dissolved in water
Some general properties of acids include sour taste, reactivity with metals, and ability to produce color changes in indicators
Definition: an indicator is any substance that changes color in the presence of an acid or a base

33. Bases
Definition: a base is a compound that produces hydroxide ions (OH-) when dissolved in water
Some general properties of bases include bitter taste, slippery feel, and ability to produce color changes in indicators

35. Neutralization and salts

36. Ted-ed
The strengths and weaknesses of acids and bases - George Zaidan and Charles Morton

37. Proton Donors and acceptors
Acids: proton donors
Ex: HCl, HNO3, H2CO3
Bases: proton acceptors
- or donates (OH-)
Ex: NH3, NaOH, KOH

39. 8.4 Strengths of acids and bases
The pH scale
Strong vs. weak acids and bases
Buffers
Electrolytes

40. PH video

42. Strength of Acids and Bases
Objective:
1. define pH and relate pH to hydronium ion concentration
Definition: pH of a solution is a measure of its hydronium ion concentration

43. A pH of 7 indicates a neutral solution
Water is the standard for pH 7
Water self-ionizes and has a concentration of 1.0 x10-7 M hydronium ions
pH scale runs from 0 – 14
The lower the pH, the higher the higher the hydronium ion concentration

44. The higher the hydronium ion concentration, the more acidic the substance is
A high pH value means a low H3O+ concentration
The lower H3O+ concentration, the more basic or alkaline the solution is

45. PH 1 = H3O+ conc. of 1 x 10-1
PH 2 = H3O+ conc. of 1 x 10-2
Therefore, each the difference between each pH level is 10x, not 2x

47. Phet
PH scale

48. Strong acids dissociate completely in water Ex: HCl
Strong vs Weak acids and bases
Strong acids dissociate completely in water
Ex: HCl
Weak acids dissociate partially in water
Ex: H2CO3
“Strong” acids are not necessarily strong, and “weak” does not necessarily mean weak; this depends on concentration of acid used

50. Comparing “strong” vs. “weak” acids
Mini-lab, 1M Hcl, indicator and vinegar
Comparing “strong” vs. “weak” acids
Making pH 3 solutions with a weak acids and a strong acid
Compare the amount of strong acid and weak acid you had to add; even though you’re trying to make equal pH solutions why aren’t the amount of each acid you use equal?

51. Buffer – a solution that is resistant to large changes in pH

52. Buffers can act as acid or a base Buffers are present in human body
Weak acids and bases can act as “buffers” because the undissociated molecules buffer the change in pH when other acids/ bases are added
Buffers can act as acid or a base
Buffers are present in human body

53. All about that base https://www.youtube.com/watch?v=IAJsZWhj6GI

54. Electrolytes
Electrolyte – a substance that ionizes or dissociates into ions when it dissolves in water
Electrolytes carry electricity and electrical potential across cell membranes

55. Electrolyte video