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Miha Lee Lesson Plan Chapter 22. Acids, Bases and Salts Subject: 8th grade Physical Science 18th Week (5 periods)
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Page 1: Lesson Plan Asid Alkali

Miha Lee

Lesson Plan Chapter 22. Acids, Bases and SaltsSubject: 8th grade Physical Science 18th Week (5 periods)

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(A) Major Concepts

General properties of acids and bases

Acids are proton donors

Bases are proton acceptors

Strength of acids and bases

Salt formation

Indicators and pH scale

What is acid rain ?

(B) Performance Objective / Content Standards

When the lesson is complete, students will be able to…..

Classify acids and bases according to their properties. => knowledge,

comprehension, analysis, evaluation, inductive reasoning => 5e. Students know

how to determine whether a solution is acidic, basic, or neutral.

Recognize acids as proton donors and bases as proton acceptors. =>

knowledge, comprehension, analysis, deductive reasoning => 5e. Students

know how to determine whether a solution is acidic, basic, or neutral.

Interpret warning and safety labels on products containing acids and bases. =>

knowledge, comprehension, application, evaluation, critical thinking

Compare and contrast the strength of an acid or base with its concentration. =>

knowledge, comprehension, application, analysis, evaluation, inductive

reasoning.

Describe the process of neutralization. => knowledge, comprehension,

synthesis, deductive reasoning => 5a. Students know reactant atoms and

molecules interact to form products with different chemical properties. 5c.

Students know chemical reactions usually liberate heat or absorb heat. 5e.

Students know how to determine whether a solution is acidic, basic, or neutral.

Explain how antacids work to reduce acidity. => knowledge, comprehension,

application, synthesis, evaluation, deductive reasoning => 9a. Plan and conduct

a scientific investigation to test a hypothesis.

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Describe how indicators can be used to classify solutions as acidic or basic. =>

knowledge, comprehension, application, synthesis, evaluation, creative thinking

Compare and contrast normal rain and acid rain. => knowledge,

comprehension, application, analysis, inductive reasoning

Compare the natural and industrial sources of acid rain. => knowledge,

comprehension, application, analysis, synthesis, evaluation, inductive reasoning

List the effects of acid rain. => knowledge, application, evaluation

(C) Materials and Equipment

Activity 22.1 Properties of acids and bases in aqueous solution:

7 small test tubes, 2 corks to fit the test tubes, red and blue litmus paper,

baking soda, magnesium turnings, vinegar, lemon juice, carbonated water, washing

soda, soap solution, unknown solution (diluted ammonia water), 10mL graduated

cylinder, safety goggles, lab apron

Demonstration 1: Disappearing ink available in many toyshops.

Demonstration 2: raw eggs of the same size, acetic acid solution, hydrochloric

acid solution. Timer.

Demonstration 3: a head of red cabbage, heating mantle, vinegar, baking soda,

ammonia water, 0.1 M HCl solution

Activity 22.2 Neutralization and pH change

1.0 M HCl, NaOH solutions, BTB solution, 5 Styrofoam containers, pH paper,

20mL graduated cylinder, thermometer, 2 250mL beakers

(D) Outline of Lesson (provide a general time frame)

Period Activity Content Time (min.)

1 Warm-up Vocabulary 5

Introduction Introduction of the chapter 22 5

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Lab Experiment Common properties of acids & bases 30

Discussion Discussion of the results from the lab. 17

2

Warm-up Tastes of Foods 5

Demonstration Disappearing ink 10

Lecture Definitions of acids and bases 30

Group work The strength of acids and bases 10

Summary Assigning homework 1 2

3

Discussion The strength of acids and bases Safety

and reading labels30

Demonstration Removing the shell from a raw egg

without breaking the egg.5

Introduction Section 22.2 Neutralization and pH 5

Lecture Neutralization Reaction Salt

formation, Antacid15

Summary Finding the Result of demonstration

Assigning homework 22

4 Warm-up Vocabulary 5

Demonstration Cabbage juice indicator 10

Discussion Indicators and pH scale 30

Lecture Acid rain 10

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Summary Assigning homework 3 2

5

Lab experiment Activity 22.2 Neutralization reaction 30

Discussion Neutralization and pH change 17

Summary Chapter review 10

(E) Lesson activity

(1) Warm-up/Dispatch Activity

1. Section 22.1: Vocabulary – find the meaning of the vocabulary

listed in the board with your textbook glossary. (5 min.)

Acid

Acid

anhydride

Base

Basic

anhydride

Electrolyte

Organic acid

2. Taste of Foods: write down the names of foods you ate this morning

and their tastes.

3. Section 22.2: Vocabulary – find the meaning of the vocabulary

listed in the board with your textbook glossary. (5 min.)

Alkalosis

Indicators

Neutralization reaction

Neutral solution

PH scale

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Salts

Antacid

(2) Introduction. How does today's lesson relate to past lessons?

1. Introduction of Chapter 22. and Section 22.1.1 (10 min.)

Read and answer the question: Why do some hydrangeas have pink flowers, while

others have blue flowers? (Text book pp.540~541)

This chapter is a part of Unit 7 ‘chemical system’ which consists of chapter 21.

Chemical reactions, chapter 22. Acids, bases and salts, and chapter 23. The

environmental and chemical technology. In this unit, students learn about what

happens and how it affects our life when chemical reactions take place. Especially,

Chapter 22. Acids, Bases and Salts is introduced as a representative chemical

reaction which is closely related to our life. From this chapter, students will learn

how to classify substances based on their properties and what indicates a chemical

reaction (neutralization) occurring. These are review of former Unit. 5 Matter and

former Chapter. 21.

Look at the concept map of the chapter.

Introducing Learning objectives

2. Section 22.1.2: Demonstration –Disappearing ink

Disappearing ink contains the indicator thymolphthalein. When squirted onto a

cloth, the blue color is visible. This will dissipate as the CO2 gas from the

atmosphere dissolves into the solution and neutralize the slightly basic solution. I

will challenge students to explain this phenomenon. This demonstration shows

that CO2 gas is an acid anhydride of carbonic acid.

3. Section 22.2: Neutralization and pH

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Acids and bases are substances. And substances undergo chemical reactions.

When an acid reacts with a base, both of them lose their properties and become

new substances. How do we know a chemical reaction take place, especially

neutralization reaction?

Watch a demonstration with red cabbage juice and answer the question: What

causes the color change of red cabbage juice?

4. Section 22.3: Acid Rain

The concept of acid rain is related to the concept of pH and acid anhydride. Most

pollutants of acid rain are nonmetallic oxides, which are acid anhydride.

(3) Lecture/discussion (Lecture notes)

Section 22.1 Recognizing Acids and Bases

22.1.1Common properties of acids and bases dissolved in

water (Textbook p.542~544)

Classify acids and bases according to their properties.

1. Emphasize that as elements are grouped in the periodic

table in terms of their atomic structures and properties,

chemical compounds can be grouped according to their

properties.

2. During the lab activity, students will fill out handout 1.

3. After lab activity 22.1(it takes 30 min.), discuss the

general properties of acids and bases as an activity of

drawing conclusions.

4. During the activity, the hydrogen gas will be identified by

combustion as a teacher demonstration. This confirms

that every acid has hydrogen atom in its molecule. I will

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use this fact when the definition of acids is taught.

5. During this activity, students will develop inductive

reasoning skills finding common properties of acids and

bases.

6. The properties will be summarized a table as a graphic

organizer with two columns (diagram 1) to make it easy

to compare and contrast the properties of acids and

bases.

7. I will challenge students to compare the results of their

knowns and the unknown I provide. I use diluted

ammonia solution as an unknown solution. This fact will

be used when I teach the definition of bases.

8. I give them a chemical equation that explains the

reaction of acids with carbonates and metals.

Reactions of acids with

Metals: Zn + 2HCl → ZnCl2 + H2

Carbonates: 2HCl + CaCO3 → CaCl2 + H2O + CO2

9. Remind the reactivity of metals from chapter 21 to

explain the reactivity of acids with active metals.

22.1.2 Acids are Proton Donors (Textbook p.545~546)

Recognize acids as proton donors and bases as proton

acceptors.

1. All acids produce hydrogen gas when they react with

active metals such as Mg and Zn. This means acids has

hydrogen atom in their molecules.

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2. All acids are electrolytes that generate hydrogen ions.

3. Arrhenius’ definition is first introduces with diagram 2

and later Bronsted-Lowry definition is taught.

Arrhenius’ definition of acids: Acids in water produce

hydrogen ions (H+). HA → H+ + A-

Bronsted-Lowry definition of acids: Acids are proton

donors. HA + H2O → H3O+ + A-

4. As demonstrated in the introduction activity, acid

anhydrides are introduced as acidic substances. This will

be connected to the pollutants of the acid rain.

Acid anhydrides: nonmetal acids readily form acids

upon the addition of water.

SO3 + H2O → H2SO4, CO2 + H2O → H2CO3

5. To help students understand the definition of acids, I will

have them practice the ionization process of acids with a

handout 2.

6. When an acid is added to water, it reacts, which is a

chemical change called ionization. Acids are compounds

that are capable of donating a proton (hydrogen ion) to a

water molecule to form a hydronium ion (H3O+).

7. Organic acids have at least a group of COOH instead of H.

Many foods which taste sour includes organic acids. For

example, vinegar has acetic acid, CH3COOH, yogurt has

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lactic acid, C2H5OCOOH.

22.1.3Bases are Proton Acceptors (Textbook p.546~547)

Recognize acids as proton donors and bases as proton

acceptors.

1. All bases are electrolytes that generate hydroxide ions.

2. Arrhenius’ definition is first introduces and later Bronsted-

Lowry definition is taught.

Arrhenius’ definition of bases: Bases in water produce

hydroxide ions (OH-). BOH → B+ + OH-

Bronsted-Lowry definition of bases: Bases are proton

acceptors. B + H2O → BH+ + OH-

3. Ammonia gas doesn’t have hydroxide ion in its molecule,

but when it dissolved into water, it accepts a proton from

water molecule and becomes basic.

4. Basic anhydrides are metal oxides which readily

form bases upon the addition of water.

MgO + H2O → Mg(OH)2, CaO + H2O → Ca(OH)2

5. To help students understand the definition of bases, I will

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have them practice the ionization process of bases with a

handout 2.

22.1.4 Strength of Acids and bases (Textbook p.548~549)

Compare and contrast the strength of an acid or base with its

concentration.

Interpret warning and safety labels on products containing acids

and bases.

1. This section will begin with group work with handout 3. In

this activity, students will think about what is acidity and

what acidity depend on.

Acidity: Degree of being acidic. It depends on the

concentration of hydrogen ions in a solution.

2. I will emphasize the difference between strong acid and

more acidic. Strong acids are acids (bases) that have a

higher degree of ionization. Thus, even small amount of

molecules can produce large number of hydrogen ions

(hydroxide ions) resulting in strong acidity (basicity). Even

weak acid can produce large number of hydrogen ions when

a large amount of molecules are dissolved into water leading

to be more acidic.

Strength of an acid: indication of the extent that the acid

molecules break apart to release hydrogen ions.

(=Degree of ionization)

Strong acids: almost all the molecules break apart to

release hydrogen ions. Ex) HCl, H2SO4, HNO3…

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Weak acid: Only part of the molecules break apart to

produce fewer hydrogen ions than a strong acid of the

same concentration. Ex) CH3COOH, H2CO3, H3PO4….

Strength of a base: indication of the extent that the base

molecules break apart to release hydroxide ions.

(=Degree of ionization)

Strong bases: almost all the molecules break apart to

release hydroxide ions. Ex) NaOH, KOH, Ca(OH)2…

Weak acid: Only part of the molecules break apart to

produce fewer hydroxide ions than a strong base of the

same concentration. Ex) Mg(OH)2, NH3, Al(OH)3…..

3. Students often equate acids with corrosion, but most of

foods we eat are acidic. While some acids are corrosive – i.e.,

battery acid (sulfuric acid) and muriatic acid (hydrochloric

acid) – others are weak acids and a regular part of our diet,

including vinegar (which is about 5% acetic acid), orange

juice (citric acid), and vitamin C (ascorbic acid).

4. Many cleaning agents used, including ammonia (an aqueous

solution of ammonia gas) and lye (sodium hydroxide), are

bases. These can be dangerous because sodium hydroxide

can cause serious chemical burns.

5. Strong acids and most concentrated weak acids are

dangerous, causing severe burns for even minor contact.

Generally, acid burns are treated by rinsing the affected area

abundantly with running water (15 minutes) and followed up

with immediate medical attention. In the case of highly

concentrated acids, the acid should first be wiped off as

much as possible, otherwise the reaction of the acid

dissolving in the water could cause severe thermal burns. In

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addition to dangers from the acidity, even dilute solutions of

weak acids may also be dangerous, due to toxic or other

effects of the ions involved.

NFPA Code for NaOH: H 3; F 0; R 1

F0- not combustible. Contact with moisture or water may generate sufficient heat

to ignite combustible substances.

H3 - highly dangerous to health

R1 - reactive

MSDS: http://avogadro.chem.iastate.edu/MSDS/NaOH.htm

NFPA Code for HCl: H 3; F 0; R 2

F0- not combustible. Contact with moisture or water may generate sufficient heat to

ignite combustible substances.

H3 - highly dangerous to health

R1- very reactive

MSDS : http://nationaldiagnostics.com/images/HS-105.pdf

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6. Demonstration that shows the difference between strong acid

and weak acid will be held. Acetic acid and hydrochloric acid of

the same concentration are used to remove the shell of raw

eggs. Compare the time that takes to remove the shell of raw

egg.

Section 22.2 Neutralization and pH

22.2.1. Salt formation and antacid (Textbook p.550~552)

1. An acid reacts with a base to form water and a salt. This is a

special type of double replacement reaction called

neutralization reaction. Water is not an acid or base. It is

neutral. When an acid and a base form water, they lose their

acidic and basic properties.

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Neutralization Reaction: double replacement reaction

HA + BOH → H2O + BA Acid base water salt

2. Salts are ionic compounds that can be produced by the

neutralization reaction of an acid by a base. A large number

of salt exist, but each contains a positive ion (other than H+)

and a negative ion (other than OH-).

3. to understand of the process of neutralization, students will

practice with handout 4.

4. Antacids consist of weak bases, such as carbonates,

bicarbonates, or hydroxides. People have haertburn when

their stomach make too much hydrochloric aicd. To reduce

the acidity of stomach juice, antacids are used to cause

neutralization of HCl. Like all drugs, antacids also have some

sideeffect. If antacids are abused, alkalosis results from

higher than normal amounts of base in the blood.

22.2.2. pH scale and indicators (Textbook p.552~556)

1. This section will begin with a demonstration. In a

demonstration, red cabbage juice will be introduced as an

indicator. Students will be challenge to explain what causes

colors to change. Also, I will use two kinds of acids of the

same concentration and ask students how we can determine

the acidity of each solution.

2. With diagram 3, I explain the concept of indicator.

Indicators are organic compounds whose color is

dependent on the H+ concentration of a solution. They

change color as a result of gaining or losing H+ ions.

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3. If we compare the acidity of two solutions from the

demonstration, we need to know how much the concentration

of hydrogen ions in each solution. The pH scale provides

information about the concentration of H+ in a solution. The

pH scale was designed for use with dilute solutions. It is a

range of numbers from 0~14. (Diagram 4)

pH < 7: acidic pH = 7: neutral pH > 7: basic

The less a pH of a solution, the more acidic it is. Each

step in the pH scale corresponds to a tenfold change in

concentration of the H+ ion.

Section 22.3 Acid Rain

22.3.1. Acid rain (Textbook p.557~559)

1. The pH of normal rain or snow is about 5.6. This slight acidity

of normal rain is a result of dissolved carbon dioxide which

produces a dilute solution of carbonic acid. I will have

students recall the concept of acid anhydride learned in

section 22.1.

CO2 + H2O → H2CO3 → H+ + HCO3-

2. Acid rain is defined as rainfall that is more acidic than

pH 5.6.

3. Acid rain is caused by sulfur oxides and nitrogen oxides.

Primarily SO2, SO3, NO and NO2. They are released by natural

and man-made sources.

SO2 + H2O → H2SO3 SO3 + H2O → H2SO4

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4. Major sources of sulfur and nitrogen oxides are power

generation plants, petroleum refineries, industrial furnaces

and automobiles. Coal with high sulfur content is a serious

pollutant.

5. Acid rain damages a ecosystem and stone buildings. A

relationship between high acidity in lakes and reduced fish

populations has been established. Acid rain has also been

linked to decreased soil fertility and reduced crop and forest

yields.

6. Acid rain also causes the decomposition of stone buildings

and statues. As learned, acid can react with carbonates to

produce CO2 gas. H2SO4 + CaCO3 → CaSO4 + H2O + CO2

22.3.2. Neutralization reaction and pH change

1. In activity 22.2 with handout 5, students will learn a

characteristic of chemical reaction. Neutralization reaction is

exothermic, which means this reaction produce heat.

2. The pH change will be monitored using pH paper and an

indicator.

3. After the activity, discussion will take place about the

neutralization and pH change.

Number of H+ > Number of OH- : acidic , pH <7

Number of H+ < Number of OH- : basic , pH >7

Number of H+ = Number of OH- : neutral , pH =7

4. With handout 6, student will understand the process of

neutralization reaction.

Diagrams 1

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22.1.1 Common properties of acids and bases dissolved in

water

Acids

1. Taste (sour) (when

diluted enough to be

safely tasted)

2. Conduct electricity =>

(electrolytes)

3. Turn blue litmus red

4. React with active

metals to produce

(hydrogen gas)

5. React with carbonates

to produce (carbon

dioxide gas)

6. React with bases to

form salts

Bases

1. Taste (bitter) (when

dilute enough to be

safely tasted)

2. Conduct (electricity)

=> (electrolytes)

3. Turn red litmus blue

4. Do not react with most

metals to produce

hydrogen gas

(exceptions are Al, Zn,

and Cr)

5. Feel (slippery)

6. React with acids to

form salts

Diagram 2 : Arrhenius’ definition of acids and bases

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Diagram 3: Colors of indicators in various solutions.

Diagram 4: the pH scale

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Handout 1 (Textbook p.544)

ACTIVITY 22.1 PROPERTIES OF ACIDS AND BASES IN AQUEOUS

SOLUTION (30MIN.)

Purpose: To observe and describe the properties of some common

acids and bases and to use these observations to classify an

unknown solution.

Procedure

1. Put on your safety goggles and lab apron.

2. With a grease pencil, number seven test tubes from 1 to 7.

3. Place a pea size amount of washing soda into test tube number 4.

Similarly, place a pea size amount of baking soda in test tube

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number 5. Add water so the test tubes are about half full. Cork the

test tubes and shake to dissolve the solids.

4. Half fill the remaining test tubes with solutions, as listed in the data

table.

5. Using a new piece of red litmus for each solution, dip it into the

solution and record the color that you observe.

6. Repeat step 5 with blue litmus paper. Dispose of all litmus paper in

the trash.

7. Drop a pea-size amount of baking soda into each of the solutions.

Record your observations.

8. Clean and rinse the test tubes. Repeat steps 3 and 4. Drop a small

piece of magnesium into each test tube and record your results.

9. Before leaving the laboratory, clean up all materials and wash your

hands thoroughly.

Collecting and Analyzing the Data

SolutionObservations

Litmus Soda Mg

Vinegar

Lemon juice

Carbonated water

Washing soda

Baking soda

Soap

Unknown

1. What pattern do you notice for the solutions in the first three test

tubes?

2. What patterns do you notice for the solutions in the other three test

tubes?

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Drawing Conclusions

3. Solutions in the first three test tubes are acids. Solutions in the last

three test tubes are bases. How is each group similar?

4. Use your data to classify the unknown as an acid or a base. State

evidence for your answer.

Handout 2: Fill out the Ionization Process (I made it)

Ionization of common acids

Acid Ionization Process

HCl HCl → H+ + Cl-

H2SO4 H2SO4 → 2H+ + SO42-

HNO3 HNO3 → H+ + NO3-

H2CO3 H2CO3 → H+ + HCO3- → 2H+ + CO3

2-

CH3COOH CH3COOH → H+ + CH3COO-

Ionization of common bases

Base Ionization Process

NaOH NaOH → Na+ + OH-

KOH KOH → K+ + OH-

Ca(OH)2 Ca(OH)2 → Ca2+ + 2OH-

Ba(OH)2 Ba(OH)2 → Ba2+ + 2OH-

Mg(OH)2 Mg(OH)2 → Mg2+ + 2OH-

NH3 NH3 + H2O → NH4+ + OH-

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Handout 3 (I made it)

ACTIVITY 22.2 STRENGTH OF ACIDS AND BASES IN AQUEOUS SOLUTION

(20MIN.)

Purpose: To describe the concentration and acidity of acids and to

classify weak and strong acids.

Procedure

A B

1. See the diagrams that have molecular and ionic models in a

container.

2. Count the total number of acid molecules that were added to

water in each container.

3. Count the total number of hydrogen ions that are in water of

each container.

4. Calculate the degree of ionization with the following equation.

Degree of ionization = (the total number of hydrogen

ions in water)/(the total number of acid molecules added

to water)

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Collecting and Analyzing the Data

A B

The total number of acid

molecules added to water

The total number of

hydrogen ions in water

Degree of ionization

Acidity

Drawing conclusions

1. What causes an acid to be acidic?

2. What does the acidity of a solution depend?

3. Which one is a strong acid? Why?

Handout 4 (I made it)

Neutralization of acids and bases: Fill out the vacancy with appropriate

numbers and chemical formulas.

① HNO3  +  (KOH) →  KNO3  +  H2O

② 2HCl  +  Mg(OH)2  →  MgCl2  +  (2H2O)

③ (H2SO4) +  2NaOH  →  Na2SO4  +  2H2O

④ 2HClO4  +  (Ca(OH)2) →  Ca(ClO4)2  +  2H2O

Handout 5 ( I made it.)

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Activity 22.2 Neutralization reaction and pH change.

(30min.)

Purpose: Describe the changes in a neutralization reaction in terms

of temperature, pH and color of an indicator.

Procedure

1. Prepare HCl and NaOH solutions of the same concentration with

large beakers from the teacher’ table. Then measure the

temperatures of the solutions.

2. With a graduated 20mL cylinder, measure the volume of each

solution and pour it to the Styrofoam container as listed in the

data table.

3. Mix well two solutions and measure the temperature of the

mixed solution. Record the temperature in the data table.

4. Then dip small strip of pH paper into the mixed solution.

Compare the changed color to the color reference chart on the

side of the container. Record the pH in the data table.

5. Drop BTB solution into the mixed solution and observe the color.

Record the color in the data table.

6. Repeat the whole step with different volume of each solution as

listed in the data table.

Collecting and Analyzing the Data

Solution

No.

Volume of

HCl (mL)

Volume of

NaOH

(mL)

Temperature

(C)

pH Color of

BTB

1 40 0

2 30 10

3 20 20

4 10 30

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5 0 40

1. Which solution shows the highest temperature?

2. Which solution is acidic?

3. Which solution is neutral?

4. Which solution is basic?

5. What color is for BTB in acidic solutions?

6. What color is for BTB in basic solutions?

7. What color is for BTB in neutral solutions?

Drawing conclusions

8. Why some solution is still acidic or basic?

9. What causes the temperature to rise?

10. Which solution is neutralized perfectly?

11. How do we know which solution is neutralized perfectly?

Handout 6

IONIC MODEL OF NEUTRALIZATION REACTION

Purpose: Explain the change in a neutralization reaction with ionic models.

Procedure: Examine the diagrams and answer the questions.

Step 1.

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1. What is in the beaker?

2. Is the solution in the beaker acidic or basic? Why?

3. What is in the spoid?

Step 2.

4. Is the solution in the beaker acidic or basic? Why?

5. What happened during the step 1?

Step 3

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6. Is the solution in the beaker acidic or basic? Why?

7. What kind of salt is in the beaker?

Step 4

8. Is the solution in the beaker acidic or basic? Why?

(4) Activities

Group work: Strength of acids and bases

Laboratory experiments

1. Activity 22.1 Properties of acids and bases in aqueous

solution (Textbook p. 544) See handout 1

2. Activity 22.2 Neutralization reaction. See handout 5

Demonstrations

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1. Disappearing ink

2. Removing the shell from a raw egg without breaking the

egg.

3. Cabbage juice indicator.

(F) Homework

Homework 1:research about the uses of common acids and bases in our life.

Homework 2: solve the problems of lesson review 22.1 (Textbook p.549)

Homework 3: solve the problems of lesson review 22.2(Textbook p.556) and

chapter review (Textbook p. 562~563)

Readings: Physical Science, the Challenge of Discovery, Heath. Chapter 22. p.

540~563)

(G) References

Textbook: Carle, Sarquis, Nolan, 1991, Physical Science, The Challenge of Discovery, D.C.

Heath and Company, Lexington, Massachusetts.

http://www.chemtutor.com/acid.htm

http://dl.clackamas.edu/ch105-05/properti.htm

http://staff.jccc.net/PDECELL/chemistry/phscale.html

http://www.edb.utexas.edu/insite/iste-test/pbiprojects/Fall2000/GrnChem/content/

lesson3.htm