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

5. 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

6. 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

7. 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

8. 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

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

10. 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

11. 8.2 Solubility and Concentration
Objectives:
1. Define solubility and describe factors affecting solubility
2. Classify solutions as unsaturated, saturated or supersaturated

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. A pH of 7 indicates a neutral solution
Water is the standard for pH 7
The pH scale runs from 0 – 14
The lower the pH, the higher the higher the hydronium ion concentration

19. 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