1. Solutions, Acids, and Bases
Chapter 8
Solutions, Acids, and Bases

2. 8-1 Formation of Solutions
Substance can dissolve in water three ways-by dissociation, dispersion, and ionization
A solute is a substance whose particles are dissolved in a solution.
The substance in which the solute dissolves is called the solvent.
Ex: Seawater
Solute = is the salt
Solvent = is the water

3. Solutes/Solvents
Solutes and solvents can take the form of a solid, liquid or gas.
The solution takes the state of the solvent.

4. Dissociation of Ionic Compounds
Dissociation is the process in which an ionic compound separates into ions as it dissolves.
For a solute to dissolve in water, the solute and solvent particles must attract one another.
Before a solution can form, the attractions that hold the solute together and the solvent together must be overcome

5. Dispersion of Molecular Compounds
Sugar dissolves in water by dispersion, or breaking into small pieces that spread throughout the water.
Ex: piece of candy disperses throughout your mouth
Water in saliva dissolves the sugar and flavoring in the candy.

6. Process of Dispersion
When enough water molecules surround a sugar molecule, the attractions between them are great enough to overcome the attractions holding the sugar molecule to the surface of the crystal.
The sugar molecule breaks free, and is pulled into solution by the water molecules, then another layer if sugar molecules is exposed to the water

7. Ionization of Molecular Compounds
The process in which neutral molecules gain or lose electrons is known as ionization.
Dissolving by ionization is a chemical change.
The solution that results contains new substances.
When a solute dissolves by ionization, the ions in solution are formed by the reaction of solute and solvent particles.

8. Example of Ionization
When water and hydrogen chloride form a solution, two molecular compounds react to form two ions.
Ions formed are H3O+ and Cl-
Drawing

9. Answer the following Questions
What are three ways that substances can dissolve in water?
How does sugar dissolve in water?

10. 8-1 Continued Properties of Liquid solutions
Three physical properties of a solution that can differ from those of its solute and solvent are:
Conductivity
Freezing Point
Boiling Point

11. Conductivity Solid sodium chloride is a poor conductor of electricity
Sodium chloride dissociates in water and the ions formed can move freely enabling them to conduct electricity

12. Freezing Point
The freezing point of water at sea level is 0 degrees Celsius
Example : icy roads are salted with magnesium chloride, the resulting solution can have a freezing point as low as -15 degrees Celsius

13. Boiling Point A solute can raise the boiling point of the solvent
Example: the coolant used in most car radiators is a solution containing water and ethylene, which raises the boiling point. This helps the engine from overheating.

14. Heat of Solution
During the formation of a solution, energy is either released or absorbed.
In order for a solution to form, both the attractions among the solute particles and the attractions among the solvent particles must be broken.
Breaking attractions requires energy.

15. Heat of Solution Continued
As the solute dissolves, new attractions form between solute and solvent particles.
The formation of attractions releases energy.
The difference between these energies is known as heat of solution

16. Factors Affecting Rates of Dissolving
Factors that affect the rate of dissolving include:
Surface area
Stirring
Temperature

17. Surface Area
The greater the surface area of a solid solute, the more frequent the collisions are between solute and solvent particles.
More collisions result in faster rate of dissolving

18. Stirring
Stirring moves dissolved particles away from the surface of the solid, and allows for more collisions between the solute and solvent particles

19. Temperature
Increasing the temperature of the solvent speeds up the dissolving rate.
This causes its particles to move faster.
As a result, both the number of collisions and the energy of these collisions with solute particles increase.
The solute goes into the solution more quickly.

20. Beaker Breaker
List the three factors that affect the rate of dissolving.
Sugar dissolves in water by___________, or breaking into small pieces that spread throughout the water

21. Section 8-1 Review Using your book complete the following questions:
Page 257
Numbers 1,2,3,4,5

22. Section 8-2
The maximum amount of a solute that dissolves in a given amount of solvent at a constant temperature is called solubility
Ex: sugar in lemonade
Knowing the solubility of a substance can help you classify solutions based on how much solute they contain.

23. Solubility Solutions are described as: saturated, unsaturated,
Supersaturated
depending on the amount of solute in solution.

24. Saturated Solutions Table sugar is very soluble in water
A saturated solution is one that contains as much solute as the solvent can hold at a given temperature.
When a solution is saturated, the solvent is “filled” with solute.
If you add more solute, it will not dissolve.

25. Unsaturated Solutions
A solution that has less than the maximum amount of solute that can be dissolved is called an unsaturated solution.
Example: many beverages you drink are unsaturated solutions of sugar in water.
As long as the amount of solute is less than the solubility at that temperature, the solution is unsaturated

26. Supersaturated Solutions
A supersaturated solution is one that contains more solute than it can normally hold at a given temperature.
Supersaturated solutions are very unstable.
Ex: carrying a stack of books

27. Review Questions
What terms are used to describe solutions with different amounts of solute.
How does a supersaturated solution differ from a saturated solution?

28. How Cold Packs Work
Read page 233 in your book
Discussion

29. 8-2 Continued Factors Affecting Solubility
Three factors that affect the solubility of a solute are:
The polarity of solvent
Temperature
Pressure

30. Polar and Nonpolar Solvents
Oil does not dissolve in water because oil molecules are nonpolar and water molecules are polar
A common guideline for predicting solubility is “like dissolves like”
Solution formation is more likely to happen when the solute and solvent are either both polar or both nonpolar

31. Temperature
In general, the solubility of solids increases as the solvent temperature increases.
Example: sugar added to cold tea verses hot tea
Gases usually become less soluble as the temperature of the solvent increases

32. Pressure
Increasing the pressure on a gas increases its solubility in a liquid
Carbonated beverages, uses pressure to force CO2 to dissolve in the liquid
The pressure of CO2 in a sealed 12-ounce can of soda at room temp can be two to three times atmospheric pressure.

33. Concentrations of Solutions
The concentration of a solution is the amount of solute dissolved in a specified amount of solution
Concentrations can be expressed as percent by: volume, percent by mass, and molarity.

34. Percent by Volume Percent by Volume = Volume of solute x 100%
Volume of solvent
Example the volume of the solute is 10 L and the volume of the solvent is 30 L. What is the percent by volume?

35. Percent by Mass
Concentration expressed as a percent by mass is more useful when the solute is a solid.
Percent by mass = Mass of solute x 100%
Mass of solution
Example: Suppose you have 100grams of a solution of sugar in water. After allowing the water to evaporate, 15 grams of sugar remains. What is the percent by mass?

36. Molarity
Molarity is the number of moles of a solute dissolved per liter of a solution.
Molarity = moles of solute x 100%
Liters of solution

37. Example of Molarity
To make 1-molar (1M) of solution of sodium chloride in water
First calculate the molar mass of the solute (NaCl) = _________
If 58.5 grams of sodium chloride is mixed with enough water to make one liter of solution, the resulting solution is 1-molar.

38. Complete the following Questions
1.)What are three ways that substances can dissolve in water?
2. What physical properties of a solution differ from those of its solutes and solvents?
3. How does the formation of a solution involve energy?
4. What factors affect dissolving rates?
5. Identify the processes by which sugar crystals and hydrogen chloride gas dissolve in water.

39. 8-3 Properties of Acids and Bases
There are several differences among acidic solutions, basic solutions, and solutions that have properties neither an acid or nor a base

40. Identifying Acids
An acid is a compound that produces hydronium ions (H3O+) when dissolved in water.
Ex: HCl + H2O H3O+ + Cl-
Some general properties of acids include sour taste, reactivity with metals, and ability to produce color changes in indicators

41. Sour Taste Foods that taste sour often contain acids
Ex: lemons, grapefruits, limes, and oranges all contain citric acid.
Vinegar contains acetic acid.
Dairy products that have spoiled contain butyric acid

42. Reactivity with Metals
When you use aluminum foil to cover a bowl of leftover spaghetti sauce or other foods containing tomatoes the foil often turns dark.
Tomatoes contain citric acid, which reacts with metals such as aluminum

43. Reactivity with Metals
The reaction between an acid and a metal is an example of single replacement reaction.
Ex: Zinc is added to hydrochloric acid. Zn +2HCl  H2 + ZnCl2
As zinc replaces hydrogen in hydrochloric acid, hydrogen gas and zinc(II) chloride is produced

44. Color Changes in Indicators
An indicator is any substance that changes color in the presence of an acid or base.
One of the most common indicators used is litmus, a kind of dye derived from plants called lichens.
Litmus paper is made by coating strips of paper with litmus.
Blue litmus paper turns red in the presence of an acid.

45. Testing Acids on litmus paper
Observations
Vinegar –
HCl –
Sulfuric Acid –
Acetic Acid -

46. Identifying Bases Sodium hydroxide, NaOH is an example of a base.
A base is a compound that produces hydroxide (OH-) when dissolved in water.
NaOH  Na+ + OH-

47. Bases
Bases have certain physical and chemical properties that you can use to identify them.
Some general properties of bases include bitter taste, slippery feel, and ability to produce color changes in indicators

48. Properties of Bases Bitter Taste Slippery Feel
Color Changes in indicators

49. Bitter Taste Baking chocolate (without the sugar)
Cough syrups and other liquid medicines

50. Slippery Feel Bases feel slippery.
Wet soap and many cleaning products that contain bases are slippery to the touch.
When wet, some rocks feel slippery because water dissolves compounds trapped in the rocks, producing a basic solution.

51. Color changes in Indicators
Bases turn red litmus paper blue.
Observations of bases
NaOH –
Ba(OH)2-
NH4OH-

52. Flowers
Hydrangeas color changes based on whether they are grown in acidic or basic soil
Acidic – flowers are bluish-purple
Basic – flowers are pink

53. End of 8-3 Neutralization and Salts
Fish contains bases that can leave a bitter taste.
Lemon juice contains an acid called citric acid.
Squeezing lemon juice on fish makes it taste less bitter
The reaction between an acid and a base is called neutralization

54. Neutralization
During neutralization, the negative ions in an acid combine with the positive ions in a base to produce an ionic compound called a salt
The hydronium ions from the acid combine with the hydroxide ions from the base to produce water.
The neutralization reaction between an acid and a base produces a salt and water.

55. Example of neutralization
(H3O+ + Cl- ) + Na+ + OH- )  2HOH + (Na+ + Cl-)
acid base water salt
Other common salts that are produced during neutralization are:
Potassium chloride – KCl – salt substitute
Potassium iodide – KI- added to table salt to prevent iodine deficiency
Magnesium Chloride – MgCl2 – De-icer for roads

56. Proton Donors and Acceptors
Acids lose or “donate” protons
Bases “accept” protons, forming water, a neutral molecule.
Acids can be defined as proton donors, and bases can be defined as proton acceptors.
Example water can act either as an acid or base depending on the compound with which it reacts.

57. Water acting as an acid and a base
Complete the following examples from the board.

58. 8-4 Strengths of Acids and Bases
Chemists use a number scale from 0 to 14 to describe the concentration of hydronium ions in a solution. It is known as the pH scale.
The pH of a solution is a measure of its hydronium ion concentration.

59. pH scale A pH of 7 indicates a neutral solution.
Acids have a pH less than 7
Bases have a pH greater than 7
See Figure 22

60. pH scale
Water is neutral because it contains small but equal concentrations of hydronium ions and hydroxide ions.
The lower the pH value, the greater the H3O+ ion concentration in solution is.
The higher the pH value, the lower the H3O+ ion concentration is.

61. Strong Acids and Bases
When certain acids and bases dissolve in water, the formation of ions from the solute almost goes to completion. Such acids and bases are classified as strong.

62. Strong Acids
When strong acids dissolve in water, they ionize almost completely.
Ex: HCl = hydrochloric acid
H2SO4 = sulfuric acid
HNO3 = nitric acid

63. Strong Bases Strong bases dissociate almost completely in water.
Examples of strong bases:
NaOH – sodium hydroxide
Ca(OH)2 - calcium hydroxide
KOH – potassium hydroxide

64. Beaker Breaker Acids have a pH range from ________to ___________
Name one property of a base _______________
Compare the pH values of acids, bases, and pure water.

65. Weak Acids and Bases
Weak acids and bases ionize or dissociate only slightly in water
The citric acid in orange juice and the acetic acid in vinegar are weak acids.
Toothpaste and shampoo contain weak bases.

66. Concentration verses strength
Concentration is the amount of solute dissolved in a given amount of solution.
Strength refers to the solute’s tendency to form ions in water.

67. Weak Acids
A weak acid forms fewer hydronium ions than a strong acid of the same concentration.
A weak acid has a higher pH than a strong acid of the same concentration.

68. Weak Bases Follows the same concept as weak acids.
Example is NH3 (ammonia) because when it dissolves in water, very little of it ionizes.

69. Buffers Weak acids and bases can be used to make buffers.
A buffer is a solution that is resistant to large changes in pH.
Buffers can be prepared by mixing a weak acid and its salt or a weak base and its salt.

70. Electrolytes
An electrolyte is a substance that ionizes or dissociates into ions when it dissolves in water.
The resulting solution can conduct electric current.
Electrolytes in sports drinks help restore the balance of ions in your body.

71. Electrolytes
Strong acids and bases are strong electrolytes because they dissociate or ionize almost completely in water.
Ex: sodium hydroxide (NaOH) is a strong electrolyte that produces many ions in water.
Acetic acid is a weak electrolyte because it only partially ionizes.

72. Examples of Electrolytes
Batteries and other portable devices that produce electricity also contain electrolytes.
Car batteries use lead plates in combination with the electrolyte sulfuric acid to produce electricity.
Space shuttles use devices called fuel cells
Fuel cells use the strong base potassium hydroxide as an electrolyte.

73. Testing strong weak acids verses strong weak bases on litmus paper
Observations
Test #1 HCl – strong or weak
acid or base
Test #2 NaOH – strong or weak
Test# 3 CH3COOH – strong or weak
Test#4 NH3 + - strong or weak