Stefanie Paternostro Terry Biondo

   Process Oriented Guided Inquiry Learning Students in small groups working through activities Content learning • Piaget Learning Cycle E Exploration Induction → Deduction I Concept Invention → A Application

Manager Recorder Strategy Analyst Reporter Facilitator Manager Recorder Strategy Analyst Reporter Manager Recorder Strategy Analyst Reporter Manager Recorder Strategy Analyst Reporter

POGIL General Chemistry at Franklin & Marshall College 8 years of data (n = 905) D,W,F 22% Lecture A 19% POGIL D,W,F 10% A 24% D, W, F Drop, Withdraw, Fail C 26% C B 26% B 33% 40% Data from classrooms of Moog, Farrell and Spencer Chi-squared = 40.9 alpha < 0.005

A, B, C Grades Earned Farrell, J.J.; Moog, R.S.; Spencer, J.N. J. Chem. Educ. 1999, 76, 570.

     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.

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?

They are dissociation reactions .

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

Each reactant yields a hydrogen ion.

Excerpt from

Activity 1 Concept Invention Question

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 HSO Brønsted-Lowry Acids.

4 are all considered Brønsted- Lowry Acids. Given your observations of the reactions above, define 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 1 Exercise (Application)

C 6 O 7 H 8, a component of citric fruit juices, would dissociate to form C 6 O 7 H 7 and H + ions. Explain how this accounts for the taste of many citric fruits.

Since C 6 O 7 H 8 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?

Model 2: pH Scale Taken from: de Dios, Angel C. Home Page of Angel C. de Dios. bouman.chem.georgetown.edu/S0 2/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?

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

1 x 10 -3

Model 2: pH Scale Excerpt from

Activity 2A Concept Invention Questions

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

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 Milk Lemon Juice Milk of Magnesia pH 6.5

2.5

10.5

[H + ] 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

Model 1: Dissociation Reactions Acid Table 1: Acid Dissociations and Concentrations Concentrations K a H 2 C 2 O 4 H 2 C 2 O 4 1.00 M HC 2 O 4 0.24 M H + 0.24 M H 2 PO 4 H 2 CO 3 H 2 PO 4 1.00 M H 2 CO 3 1.00 M HPO 4 2 6.93 x 10 -7 M H + 6.93 x 10 -7 M HCO 3 6.56 x 10 -4 M H + 6.56 x 10 -4 M

Acid Table 1: Acid Dissociations and Concentrations Concentrations K a H 2 C 2 O 4 H 2 C 2 O 4 1.00 M HC 2 O 4 0.24 M H + 0.24 M H 2 PO 4 H 2 CO 3 H 2 PO 4 1.00 M H 2 CO 3 1.00 M HPO 4 2 6.93 x 10 -7 M H + 6.93 x 10 -7 M HCO 3 6.56 x 10 -4 M H + 6.56 x 10 -4 M Looking at Table 1: A) What is the concentration of hydrogen ion produced by the dissociation of H 2 C 2 O 4 ?

0.24 M B) What is the concentration of conjugate base (HC 2 O 4 ) produced by the dissociation of H 2 C 2 O 4 ?

0.24 M C) What is the concentration of acid H 2 C 2 O 4 ?

1.00 M

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

pH is (proportional/ inversely proportional ) to K a .

15. What does your answer to question 14 mean about the strength of an acid in relationship to its K a ? The higher the K a, the stronger the acid.

Acid Table 1: Acid Dissociations and Concentrations Concentrations K a H 2 C 2 O 4 H 2 C 2 O 4 1.00 M HC 2 O 4 0.24 M H + 0.24 M 5.76 x 10 -2 H 2 PO 4 H 2 CO 3 H 2 PO 4 1.00 M H 2 CO 3 1.00 M HPO 4 2 6.93 x 10 -7 M H + 6.93 x 10 -7 M HCO 3 6.56 x 10 -4 M H + 6.56 x 10 -4 M 4.80 x 10 -13 4.30 x 10 -7 Answer 6 Answer 7 Answer 8 10. Using your answers from questions 6, 7, and 8, calculate the K a ’s of the acids listed in Table 1 and write your answer in Table 1 under the column labeled K a .

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!

Model 1: 1 st Definition of Redox Reactions

Reduction Reactions Oxidation Reactions

Model 1: 1 st 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?

2C and O 2 B) the reduction of SO 2 ?

S and O 2 C) the reduction of 2NO 2 ?

N 2 and 2O 2 2. Using your answers to question 1, what do the reduction reactions of Model 1 have in common?

An O 2 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.

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

Oxidation/Reduction Rule oxidation 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