Stefanie PaternostroTerry Biondo

Process Oriented Guided Inquiry Learning Students in small groups working through

activities Content learning

• PiagetLearning Cycle

Induction Deduction

E → I → AExploration Concept Invention

Application

Facilitator

A19%

B33%

C26%

D,W,F22%

A24%

D,W,F10%

C26%

B40%

POGIL General Chemistry at Franklin & Marshall College

Lecture POGIL

8 years of data (n = 905)

Farrell, J.J.; Moog, R.S.; Spencer, J.N. J. Chem. Educ. 1999, 76, 570.

Data from classrooms of Moog, Farrell and Spencer Chi-squared = 40.9 alpha < 0.005

D, W, FDrop, Withdraw, Fail

A, B, CGrades Earned

Introduction for the facilitator Engage the student Model Questions based on Piaget’s learning

cycle Exercises

Focus & Clarity Acceptable Forms

• Tables • Equations• Diagrams• Sets of written relationships• Short reading passage• Pictures

Explorative questions• Observations from model/previous knowledge

Concept Inventive questions• Observation + Observation concept• Discussion

Application• Concepts in action

Why?Acids and bases are used in everyday life in a variety of places: our bodies use acids to aid in digestion; acids are used in the power cells of batteries; and many ingredients in cooking have either acidic or basic properties.

Learning Objectives• Understand Arrhenius Acids and Bases• Understand reactions of Arrhenius Acids and

Bases• Understand Brønsted-Lowry Acids and Bases• Understand reactions of Brønsted-Lowry Acids

and Bases

Success Criteria• Compare Arrhenius Acids and Brønsted-Lowry

Acids• Compare Arrhenius Bases and Brønsted-Lowry

Bases• Explain the relationship between Brønsted-

Lowry Acids and Bases• Identify these acids and bases in reactions

Prerequisites• Understand parts of a chemical reaction (i.e.

products and reactants)• Have a familiarity with ions

Have you ever sucked on a lemon to get rid of your hiccups? If you have, did you stop to wonder why the lemon was sour? The answer is in the acid which the juice contains! And while these acids taste sour, bases taste bitter.

Bases + Reactant Product

HClCl- H+

HFF- H+

+

+

HSO4-

SO42- H++

Acids Products

HCl Cl- H+

HF F- H+

+

+

HSO4- SO4

2- H++

Model 3: Reactions of Brønsted-Lowry Acids

Model 4: Reactions of Brønsted-Lowry Bases

15. How do Brønsted-Lowry Bases relate to Brønsted-Lowry Acids? They are the reverse reactions of one-another.

Model 1: Dissociation Reactions of Arrhenius Acids

1. What type of reactions are these?

2. What do the products of each of these reactions have in common?

Acids Products

HCl

H2SO4

HNO3

Cl-

HSO4-

NO3-

+

+

+

H+

H+

H+

They are dissociation reactions.

Each reactant yields a hydrogen ion.

Question 3: The acids pictured in Model 1 are all Arrhenius Acids. Based on the dissociation reactions of these acids, define an Arrhenius Acid.

Answer 3: Arrhenius Acids yield hydrogen ions.Question 9: HCl, HF, and HSO4

- are all considered Brønsted- Lowry Acids. Given your observations of the reactions above, define Brønsted-Lowry Acids.

Answer 9: Brønsted-Lowry Acids yield hydrogen ions.

10.Based on your answers to questions 3 and 9, explain any differences or similarities between Brønsted- Lowry Acids and Arrhenius Acids.

Both yield hydrogen ions.

Excerpt from Activity 1Concept Invention Question

C6O7H8, a component of citric fruit juices, would dissociate to form C6O7H7

- and H+ ions. Explain how this accounts for the taste of many citric fruits.

Excerpt from Activity 1Exercise (Application)

Since C6O7H8 is yielding an H+, it is an acid, which we learned earlier tastes sour. This makes sense because citric fruits often taste sour (i.e. lemons and grapefruits).

We all know lifeguards save lives by learning how to rescue victims from the water and perform CPR, but did you know they have to also understand chemistry? It’s true! The water in a swimming pool must be kept neutral in order to keep swimmers safe. Have you ever seen the pH bottles with their little color guide? Have you ever wondered how they work?

Taken from:de Dios, Angel C. Home Page of

Angel C. de Dios. bouman.chem.georgetown.edu/S02/lect14/ph.gif (accessed 14 Apr 2008), Lect 14.

Model 2: pH Scale

3. According to Model 2:A) What is the

approximate pH of cola?

B) What is the approximate [H+] of cola?

Model 2: pH Scale

3

1 x 10-3

Question: What do you notice about the exponents of the hydrogen ion concentration and their relationship to the pH?

Excerpt from

Activity 2AConcept

Invention Questions

Model 2: pH Scale

pH = -log [H+]

The following are the more precise pH’s of several household items. Use the pH equation to calculate their [H+].

Household Item pH [H+]Milk 6.5Lemon Juice 2.5Milk of Magnesia 10.5

3.16 x 10-7

3.16 x 10-3

3.16 x 10-

11

Now that we know how to determine how strongly present an acid or base is in aqueous solution, let’s figure out how to determine strength out of solution. What if the acid or base is pure? How do we know how strong it is?

More of a bridge from Activity A to Activity B

Table 1: Acid Dissociations and Concentrations

Model 1: Dissociation Reactions

H2O4C2 HC2O4- H++

H2PO4- HPO4

2- + H+

H2CO3 HCO3- + H+

Table 1: Acid Dissociations and Concentrations

Looking at Table 1: A) What is the concentration of hydrogen ion produced by the dissociation of H2C2O4?

B) What is the concentration of conjugate base (HC2O4-) produced by the

dissociation of H2C2O4? C) What is the concentration of acid H2C2O4?

0.24 M

0.24 M

1.00 M

14. Using your answers to questions 12 and 13, circle the correct answer.

pH is (proportional/inversely proportional) to Ka.

15. What does your answer to question 14 mean about the strength of an acid in relationship to its Ka?

The higher the Ka, the stronger the acid.

10. Using your answers from questions 6, 7, and 8, calculate the Ka’s of the acids listed in Table 1 and write your answer in Table 1 under the column labeled Ka.

5.76 x 10-

2

4.80 x 10-

13

4.30 x 10-

7

Table 1: Acid Dissociations and Concentrations Answer 6

Answer 7

Answer 8

The answer comes in a type of reaction called the oxidation-reduction or redox reaction. This reaction is a process which turns the copper from that shiny color of the penny we know so well, to the blue-green color of the Statue of Liberty!

Redox!

2NO2 N2 2O2+

SO2 S + O2

2CO 2C + O2

2NO2N2 2O2+

SO2S + O2

2CO2C + O2

Model 1: 1st Definition of Redox Reactions

Reduction Reactions Oxidation Reactions

1. Under the reduction reactions of Model 1, what are the products of: A) the reduction of CO?

B) the reduction of SO2?

C) the reduction of 2NO2?N2 and 2O2

S and O2

2C and O2

2NO2 N2 2O2+

SO2 S + O2

2CO 2C + O2

2NO2N2 2O2+

SO2S + O2

2CO2C + O2

Model 1: 1st Definition of Redox Reactions

Reduction Reactions Oxidation Reactions

2. Using your answers to question 1, what do the reduction reactions of Model 1 have in common?An O2 molecule is produced in each reduction reaction.

3. Using your answer to question 2, fill in the blank for the first definition of reduction reactions.

A reduction reaction results in the loss of an oxygen molecule.

1. K K+ + e-

2. FeNO3 Fe + HNO3

Label the following half reactions as oxidation or reduction and list the rule being followed.

Oxidation/Reduction Ruleoxidation

loss of e-

reduction reduction in oxidation number

Chestnut Hill College• Dr Butler, Advisor

Franklin & Marshall College• Rick Moog• Jim Spencer

Washington College• Frank Creegan

Cheltenham High School• Donna Reinhart