Pearson Prentice Hall Pearson Prentice Hall Physical Science: Physical Science:

Concepts in ActionConcepts in ActionChapter 8Chapter 8Solutions, Solutions, Acids & Acids & BasesBases

8.1 Formation of Solutions8.1 Formation of SolutionsObjectives:Objectives:1. Describe how a substance can 1. Describe how a substance can dissolve in water by dissociation, dissolve in water by dissociation, dispersion or ionizationdispersion or ionization2. Describe how physical properties of 2. Describe how physical properties of a solution can differ from those of its a solution can differ from those of its solute and solventsolute and solvent3. Identify energy changes that occur 3. Identify energy changes that occur during formation of a solutionduring formation of a solution4. Describe factors affecting the rate at 4. Describe factors affecting the rate at which a solute dissolves in a solventwhich a solute dissolves in a solvent

Dissolving: Dissociation, Dissolving: Dissociation, Dispersion or IonizationDispersion or Ionization

Substances can dissolve in water Substances can dissolve in water by three ways:by three ways:1. dissociation1. dissociation2. dispersion2. dispersion3. ionization3. ionizationDefinition: dissociation is the Definition: dissociation is the process by which an ionic process by which an ionic compound separates into ionscompound separates into ionsEx: NaClEx: NaCl

Definition: dispersion is the process Definition: dispersion is the process by which a compound breaks into by which a compound breaks into small pieces that spread throughout small pieces that spread throughout the waterthe waterEx: sugar dissolves in waterEx: sugar dissolves in waterDefinition: ionization is the process Definition: ionization is the process by which neutral molecules gain or by which neutral molecules gain or lose electrons (forming ions)lose electrons (forming ions)Ex: hydrogen chloride gas & water Ex: hydrogen chloride gas & water react to form hydronium ion (Hreact to form hydronium ion (H33OO++) ) and chlorine ion (Cl-)and chlorine ion (Cl-)

Physical Properties: Solute & Physical Properties: Solute & SolventSolvent

Definition: a solute is a substance Definition: a solute is a substance whose particles are dissolved in a whose particles are dissolved in a solution (often a solid)solution (often a solid)Definition: a solvent is the substance Definition: a solvent is the substance in which the solute dissolves (often a in which the solute dissolves (often a liquid)liquid)Solutes and solvents can take the Solutes and solvents can take the form of solids, liquids or gasesform of solids, liquids or gasesThe solution takes the state of the The solution takes the state of the solventsolvent

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

Definition: the freezing point is Definition: the freezing point is the temperature at which a liquid the temperature at which a liquid becomes a solidbecomes a solid

Freezing point is changed with Freezing point is changed with the addition of ionic compounds the addition of ionic compounds like MgCllike MgCl22 or other ionic or other ionic compoundscompounds

The freezing point is lowered The freezing point is lowered when ionic compounds are when ionic compounds are addedadded

Definition: the boiling point is the Definition: the boiling point is the temperature a liquid substance temperature a liquid substance becomes a gasbecomes a gasCoolants used in radiators Coolants used in radiators (ethylene glycol, a molecular (ethylene glycol, a molecular substance) raise the boiling point substance) raise the boiling point of water & keeps the engine of water & keeps the engine from overheatingfrom overheatingFormation of new solutions by Formation of new solutions by the addition of ionic or molecular the addition of ionic or molecular compounds requires an energy compounds requires an energy changechange

Energy Changes & Solution Energy Changes & Solution FormationFormation

During formation of a solution, During formation of a solution, energy is either released or energy is either released or absorbedabsorbedThe process is endothermic or The process is endothermic or exothermicexothermicForming attractions releases Forming attractions releases energy (exothermic)energy (exothermic)Breaking attractions requires or Breaking attractions requires or absorbs energy (endothermic)absorbs energy (endothermic)

Factors that Affect Dissolving Factors that Affect Dissolving RateRate

Factors that affect the rate of dissolving Factors that affect the rate of dissolving include surface area, stirring and include surface area, stirring and temperaturetemperature

Dissolving takes place at the surfaceDissolving takes place at the surface

The greater the surface area, the faster The greater the surface area, the faster the dissolvingthe dissolving

Stirring or shaking makes a substance Stirring or shaking makes a substance dissolve faster by increasing the surface dissolve faster by increasing the surface area exposed to the solventarea exposed to the solvent

8.2 Solubility and 8.2 Solubility and ConcentrationConcentration

Objectives:Objectives:

1. Define solubility and describe 1. Define solubility and describe factors affecting solubilityfactors affecting solubility

2. Classify solutions as 2. Classify solutions as unsaturated, saturated or unsaturated, saturated or supersaturatedsupersaturated

Solubility & Factors Affecting Solubility & Factors Affecting SolubilitySolubility

Definition: solubility is the Definition: solubility is the maximum amount of a solute that maximum amount of a solute that dissolves in a given amount of dissolves in a given amount of solvent at a constant temperaturesolvent at a constant temperatureSolutions are classified as Solutions are classified as saturated, unsaturated or saturated, unsaturated or supersaturatedsupersaturatedThe classification depends on the The classification depends on the amount of solute in solutionamount of solute in solution

3 types of solutions3 types of solutionsDefinition: a saturated solution is one Definition: a saturated solution is one that contains as much solute as the that contains as much solute as the solvent can hold at a given temperaturesolvent can hold at a given temperature

Definition: an unsaturated solution has Definition: an unsaturated solution has less than the amount of solute that can less than the amount of solute that can be dissolvedbe dissolved

Definition: a supersaturated solution Definition: a supersaturated solution contains more solute than the solution contains more solute than the solution can normally hold at a given can normally hold at a given temperaturetemperature

8.3 Properties of Acids and 8.3 Properties of Acids and BasesBases

Objectives:Objectives:

1. Define acid and describe the 1. Define acid and describe the general properties of an acidgeneral properties of an acid

2. Define base and describe 2. Define base and describe some of the general properties of some of the general properties of a basea base

AcidsAcidsDefinition: an acid is a compound Definition: an acid is a compound that produces hydronium ions that produces hydronium ions (H(H33OO++) when dissolved in water) when dissolved in water

Some general properties of acids Some general properties of acids include sour taste, reactivity with include sour taste, reactivity with metals, and ability to produce color metals, and ability to produce color changes in indicatorschanges in indicators

Definition: an indicator is any Definition: an indicator is any substance that changes color in the substance that changes color in the presence of an acid or a basepresence of an acid or a base

BasesBasesDefinition: a base is a compound Definition: a base is a compound that produces hydroxide ions that produces hydroxide ions (OH-) when dissolved in water(OH-) when dissolved in water

Some general properties of Some general properties of bases include bitter taste, bases include bitter taste, slippery feel, and ability to slippery feel, and ability to produce color changes in produce color changes in indicatorsindicators

Strength of Acids and BasesStrength of Acids and Bases

Objective:Objective:

1. define pH and relate pH to 1. define pH and relate pH to hydronium ion concentrationhydronium ion concentration

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Definition: pH of a solution is a Definition: pH of a solution is a measure of its hydronium ion measure of its hydronium ion concentrationconcentration

A pH of 7 indicates a neutral A pH of 7 indicates a neutral solutionsolution

Water is the standard for pH 7Water is the standard for pH 7

The pH scale runs from 0 – 14The pH scale runs from 0 – 14

The lower the pH, the higher the The lower the pH, the higher the higher the hydronium ion higher the hydronium ion concentrationconcentration

The higher the hydronium ion The higher the hydronium ion concentration, the more acidic concentration, the more acidic the substance isthe substance isA high pH value means a low A high pH value means a low HH33OO++ concentration concentration

The lower HThe lower H33OO++ concentration, concentration, the more basic or alkaline the the more basic or alkaline the solution issolution is