active-learning versus teacher-centered instruction for learning acids and bases

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Active-learning versus teacher-centered instruction for learning acidsand basesBurcin Acar Sesen a & Leman Tarhan ba Science Education Department , Hasan Ali Yucel EducationFaculty, Istanbul University , Istanbul, Turkeyb Science Faculty, Chemistry Department , Dokuz Eylul University ,Izmir, TurkeyPublished online: 12 Aug 2011.

To cite this article: Burcin Acar Sesen & Leman Tarhan (2011) Active-learning versus teacher-centered instruction for learning acids and bases, Research in Science & Technological Education,29:2, 205-226, DOI: 10.1080/02635143.2011.581630

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Active-learning versus teacher-centered instruction for learningacids and bases

Burcin Acar Sesena* and Leman Tarhanb

aScience Education Department, Hasan Ali Yucel Education Faculty, Istanbul University,Istanbul, Turkey; bScience Faculty, Chemistry Department, Dokuz Eylul University,Izmir, Turkey

Background and purpose: Active-learning as a student-centered learningprocess has begun to take more interest in constructing scientific knowledge.For this reason, this study aimed to investigate the effectiveness of active-learn-ing implementation on high-school students’ understanding of ‘acids and bases’.Sample: The sample of this study was 45 high-school students (average age 17years) from two different classes, which were randomly assigned to the experi-mental (n = 21) and control groups (n = 25), in a high school in Turkey.Design and methods: A pre-test consisting of 25 items was applied to bothexperimental and control groups before the treatment in order to identify studentprerequisite knowledge about their proficiency for learning ‘acids and bases’. Aone-way analysis of variance (ANOVA) was conducted to compare the pre-testscores for groups and no significant difference was found between experimental(ME = 40.14) and control groups (MC = 41.92) in terms of mean scores (F1,43 =2.66, p > 0.05). The experimental group was taught using an active-learningcurriculum developed by the authors and the control group was taught using tra-ditional course content based on teacher-centered instruction. After the imple-mentation, ‘Acids and Bases Achievement Test’ scores were collected for bothgroups.Results: ANOVA results showed that students’ ‘Acids and Bases AchievementTest’ post-test scores differed significantly in terms of groups (F1,43 = 102.53; p< 0.05). Additionally, in this study 54 misconceptions, 14 of them not reportedin the literature before, were observed in the following terms: ‘acid and basetheories’; ‘metal and non-metal oxides’; ‘acid and base strengths’; ‘neutraliza-tion’; ‘pH and pOH’; ‘hydrolysis’; ‘acid–base equilibrium’; ‘buffers’; ‘indica-tors’; and ‘titration’. Based on the achievement test and individual interviewresults, it was found that high-school students in the experimental group hadfewer misconceptions and understood the concepts more meaningfully than stu-dents in control group.Conclusion: The study revealed that active-learning implementation is moreeffective at improving students’ learning achievement and preventing miscon-ceptions.

Keywords: acids and bases; active-learning; constructivism; learning achieve-ment; misconceptions

*Corresponding author. Email: [email protected]

Research in Science & Technological EducationAquatic InsectsVol. 29, No. 2, July 2011, 205–226

ISSN 0263-5143 print/ISSN 1470-1138 online� 2011 Taylor & FrancisDOI: 10.1080/02635143.2011.581630http://www.informaworld.com

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Introduction

The main purpose of science educators is to improve students’ understanding of sci-entific concepts. However, studies in science education have revealed that studentsat all levels hold misconceptions on conceptual knowledge, which are inconsistentwith or different from the scientific view and are unable to adequately explainobservable scientific phenomena (Acar and Tarhan 2008; Felder 1996; Herron1996; Nakhleh 1992; Osborne and Freyberg 1985; Sanger and Greenbowe 1997).

Studies in chemistry education have reported many misconceptions in variouschemistry topics (Coll and Treagust 2003; Garnet, Garnet and Hackling 1995;Sanger and Greenbowe 1997). This reveals that students commonly find chemistryto be a difficult, abstract, and problematic subject. Hence, in chemistry, whichdepends on a hierarchical network of ideas, the development of misconceptions hasthe potential to affect adversely students’ understanding of many chemical conceptsand their constructions of new concepts (Acar and Tarhan 2007; Boo and Watson2001; Garnet, Garnet, and Treagust 1990; Tarhan et al. 2008).

‘Acids and bases’ is one of the chemistry subjects considered as abstract anddifficult to understand (Banerjee 1991; Cros et al. 1986; Demircioğlu, Ayas, andDemircioğlu 2005; Hand and Treagust 1991; Nakhleh and Krajcik 1993, 1994;Sisovic and Bejovic 2000). Having important and fundamental roles to help per-ceive some facts in daily life and environmental problems, ‘acids and bases’ arerelated to many other chemistry concepts such as ‘nature of matter’, ‘stoichiometry’,‘solutions’, ‘chemical reaction’, ‘chemical equilibrium’, and ‘electrochemistry’.According to the literature review, the causes of student difficulties in acid–basechemistry have been ascribed to the existence of many misconceptions (Demerouti,Kousathana, and Tsaparlis 2004; Demircioğlu, Ayas, and Demircioğlu 2005; Hand1989; Hand and Treagust 1988; Schmidt 1997; Sheppard 1997), a poor understand-ing of the particulate nature of matter (Nakhleh and Kracjik 1993; Nakhleh 1994;Smith and Metz 1996), difficulties with the use of different models used in acid–base chemistry (Schmidt 1995; Vidyapati and Seetharamappa 1995; Sheppard 1997;Furió-Más, Calatayud and Bárcenas 2007; Kousathana, Demerouti, and Tsaparlis2005), and confusion between acid–base terminology and everyday words (Schmidt1991, 1995). Some of the related studies are reviewed in the following paragraphs.

Sheppard (2006) investigated students’ understanding of acids and bases, andindicated that the students who had considerable difficulty in acid–base chemistrywere unable to explain pH, neutralization, strength, and the theoretical descriptionsof acids and bases. The results showed that students commonly described the pHconcept as the strength of an acid or base or the amount of acid or base present. Itwas also obtained that many students described neutralization as a simple mixing ofan acid and a base, with no interaction between the particles. In addition, the causesof students’ difficulties on titration were found related to having non-scientific ideasabout neutralization, pH and the nature of chemicals.

Hand and Treagust (1991) inquired into 10th-grade students’ knowledge of acidsand bases and the existence of any misconceptions. They conducted individualinterviews and five misconceptions about acids and bases were identified. Thesewere: (1) ‘An acid is something which eats material away or which can burn you’;(2) ‘Testing for acids can only be done by trying to eat something away’; (3) ‘Neu-tralization is the breakdown of an acid or something changing from an acid’; (4)‘The difference between a strong and a weak acid is that strong acids eat material

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away faster than a weak acid’; and (5) ‘A base is something which makes up anacid’.

Ross and Munby (1991) investigated senior high-school students’ understand-ings of acid and bases concepts using a multiple-choice test and individual inter-views. In the light of these results, students’ misconceptions and lack of knowledgewere identified by comparing the concept maps drawn by students to the modelconcept map. The results of multiple-choice tests revealed that students performedbest on pH and everyday phenomena items, but understood the least about base andion concepts and had difficulties in writing and balancing chemical equations. Indi-vidual interviews and concept maps gave more detailed information about studentunderstanding, and it was identified that students understood more about acids thanbases, had particular problems with the ionic nature of acids and bases, and madeincorrect association between pH and strength of acids.

In another study by Cros et al. (1986), 400 first-year university students’ precon-ceptions of the constituents of matter and notions of acids and bases wereresearched. It was found that only 23% of the students gave purely descriptive defi-nitions of acids and bases. The students gave examples of acids easily; the most fre-quently mentioned ones were hydrochloric (93%), sulphuric (61%), and ethanoicacids (56%); but when asked to list three bases, 43% were unable to name morethan two bases. In addition, the research on the students’ understanding of pH con-cept indicated that 15% of the students remembered the pH concept incorrectly and17% of them defined it as a measurement of the degree of acidity. Furió-Más,Calatayud and Bárcenas (2007) investigated 12th-grade students’ understanding ofmacro- and sub-microconceptualization of acid–base behavior and noted that a largenumber of students knew the meaning of ionic dissociation of substances in anaqueous solution, but found it difficult to apply theoretical knowledge to discoverwhether ionic dissociation is possible or not. In addition, they had little empiricalknowledge of acid–base behavior of substances and thus, they associated the exis-tence of H or OH in the formula of substance with acid or basic reactions respec-tively.

Demircioğlu, Ayas and Demircioğlu (2005) identified high-school students’ mis-conceptions about acids and bases such as; ‘acids burn and melt everything’; ‘allacids and bases are harmful and poisonous’; ‘different pH solutions have differentcolors’; ‘pH is a measure of acidity’; ‘a strong acid does not dissociate in water,because its intra-molecular bonds are very strong’; ‘all salts are neutral’; ‘salts donot have a pH value’; ‘in all neutralization reactions, an acid and a base consumeeach other completely’; ‘a strong acid is always a concentrated acid’; ‘as the valueof pH increases, acidity increases’; and ‘species having formulas with hydrogen areacids and those having formulas with hydroxyl are bases’.

Other studies examined some parts of the subject of acids and bases. For exam-ple, Schmidt (1991) investigated the problems with the concept of neutralization,and asserted that the term ‘neutralization’ acts as a hidden persuader that leads tostudents’ misconceptions. For instance, students were led by the etymology of theword neutralization into thinking that ‘every neutralization reaction resulted in aneutral solution’; ‘a gas is produced during the neutralization of hydrochloric acidby potassium hydroxide’; ‘neither hydronium nor hydroxide ions can be found in aaqueous solution because a salt contains hydrogen and a hydroxyl group’; and ‘neu-tralization can only occur in a solution that contains strong acids and bases’. Inanother study about neutralization by Vidyapati and Seetharamappa (1995), the

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same learning difficulties were obtained. On the other hand, Chen (1993) indicatedthat most students understood that neutralization will produce salts, but they wereuncertain of the salt type. Furthermore, some students hold the misconception thatthe salt produced by neutralization is certainly table salt.

Orgill and Sutherland (2008) studied undergraduate students’ perceptions of andmisconceptions about buffers, and underlined that students struggled with under-standing how buffers function or why they are important, and they had considerabledifficulty in solving calculations involving buffers. The results of interviews indi-cated that students had difficulties in writing the chemical equation and identifyingthe pH of a buffer system, in defining weak acid/base and its conjugate base/acid,and in explaining the relations between pH, hydronium ion concentration and Ka.

Although these studies have indicated that students at all levels have difficultiesin understanding ‘acids and bases’, there are limited studies that aim to overcomethese difficulties. For this reason, the purpose of the present study was to developan active-learning treatment based on constructivist approach.

The theory of constructivism recognizes that existing concepts play an importantrole in learning new concepts (Bodner 1986). As mentioned by Garnet, Garnet andTreagust (1990) many studies of students’ understandings of science concepts arebased on constructivist theory and on the notion that existing concepts influencelearning outcomes because learners link new information with prior knowledge. Inthis way, students generate or construct new meaning. For this reason, misconcep-tions will adversely affect an individual’s subsequent learning (Bodner 1986;Ben-Zvi, Eylon, and Silberstein 1986; Brown 1992; Jonassen 1991). Furthermore,once incorrect concepts become established, they are resistant to change, and influ-ence and interact with the learning of related concepts. Knowledge is not solelyconstructed within the mind of the student; rather, interactions within a socialcontext involve learners in sharing, constructing, and reconstructing their ideas andbeliefs (Balakrishnan 2001; Jadallah 2000). The emphasis is student-centered andexperiential, the teacher is more involved in planning and guiding social interactionsthat allow students to build and test knowledge within a social context (Jadallah2000). Ultimately, these views of constructivism need to be addressed in the fieldof education. Constructivism is an epistemological view of learning rather thanteaching. Constructivists believe that certain activities and enrichments in theenvironment can enhance the meaning-making process, such as active-learningusing kinesthetic, visual and auditory modalities, creating opportunities for dialogue,fostering creativity and providing a rich, safe and engaging environment (Brooksand Brooks 1999). Therefore, according to constructivist theory, students themselvesconstruct their own understanding by taking an active role in constructing newknowledge, and their prior knowledge is important in this process (Driscoll 2005).From this view, active-learning as a student-centered learning process has begun totake more interest in constructing knowledge.

In an active-learning environment, in contrast to teacher-centered instruction, ateacher acts as a facilitator, engages active participation of students in the learningprocess, and puts less emphasis on memorizing information and more emphasison inquiry through which students develop a deeper knowledge and appreciationof the nature of science (Marx et al. 2004; National Research Council 2005;Singer et al. 2000). When students are actively involved in the learning task,they learn more than when they are passive recipients of instruction. Adler (1982,50–51) stated:


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All genuine learning is active, not passive. It involves the use of the mind, not justthe memory. It is the process of discovery in which the student is the main agent, notthe teacher. Learning by discovery can occur without help, but only geniuses can edu-cate themselves without the help of teachers. For most students, learning by discoverymust be aided. That is where teachers come in – as aids in the process of learning bydiscovery, not as knowers who attempt to put the knowledge they have in their mindsinto the minds of their pupils.

Active-learning includes a wide range of activities that share the common ele-ment of involving students in doing things and thinking about the things that theyare doing (Bonwell and Eison 1991). Active-learning, as used in this study, is theimplementation of a variety of specific student-centered instructional strategies toteach the subject of ‘acids and bases’. It includes experimental activities, brain-storm-ing, video presentations, demonstrations, computer animations, and learning togetheractivities that engage active participation of students in the learning process.

Purpose of the research

The purpose of this study was to investigate the effectiveness of active-learninginstruction on students’ understanding of ‘acids and bases’. In order to enhance thisaim the following sub-questions were investigated:

(1) What is the high-school students’ prerequisite knowledge about their profi-ciency for learning ‘acids and bases’ at the beginning of the instruction?

(2) Does active-learning instruction contribute to better conceptual understandingof ‘acids and bases’ in high-school students than traditional course contentbased on teacher-centered instruction?

(3) Is active-learning instruction more effective in preventing high-school stu-dents’ misconceptions related to ‘acids and bases’ than teacher-centeredinstruction?

Participants

The sample of this study was 45 students (average age 17 years) from two differentclasses, which were randomly assigned to the experimental (n = 21) and controlgroups (n = 25), in a high school in Turkey.

All the students in both groups were similar in socioeconomic status, with themajority of them coming from middle-class families. Regular instruction in thishigh school is commonly teacher-centered with a lecture-type format and studentspassively participate in the learning process. They only listen to their teacher, writenotes, and use textbooks as a learning material.

Instrument

The pre-test

As indicated previously, ‘acids and bases’ are related to many other chemistry con-cepts such as solubility, solution, the periodic table, electronegativity, chemicalbonding, chemical reactions, thermodynamics, and chemical equilibrium. Research-ers have underlined that the causes of student difficulties in acid–base chemistryhave been ascribed to the existence of many misconceptions related to these


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aforementioned concepts (Demircioğlu, Ayas and Demircioğlu 2005; Nakhleh andKracjik 1993; Nakhleh 1994; Smith and Metz 1996; Schmidt 1997; Sheppard1997). It is also known that, based on constructivism, existing concepts play animportant role for learning new concepts (Bodner 1986). For this reason, a pre-testconsisting of 25 multiple-choice items was developed through the literature review(Ebenezer and Gaskell 1995; Griffiths and Preston 1992; Peterson, Treagust andGarnett 1989; Sanger 2000) to identify student prerequisite knowledge about theirproficiency for learning ‘acids and bases’. The content of the test was validated byfour chemistry educators and six high-school chemistry teachers. The test waspiloted with a sample of 148 eleventh-grade students for the reliability. After theitem analysis, the reliability coefficient (KR-20) of the test was found to be 0.81.

The Acids–Bases Concept Test

The Acids–Bases Concept Test of 25 multiple-choice items with an open-endedpart, where students were required to explain the reasons for their answers, wasdeveloped to identify students’ understandings of ‘acids and bases’. Before develop-ing the test’s items, the content boundaries and instructional objectives were definedand many studies on acids and bases were reviewed to determine student learningdifficulties and misconceptions (Bradley and Mosimege 1998; Cros et al. 1986;Schmidt 1991). For the content validity and error reduction, the items were evalu-ated by four chemistry educators and six high-school chemistry teachers. The testwas piloted with a sample of 196 11th-grade students for reliability. After the itemanalysis the reliability coefficient (KR-20) of the test was found to be 0.79.

Interviews

In order to ensure the reliability of the study and also take more detailed informa-tion about students’ unclear responses, 15-minute semi-structured interviews werecarried out with five students from both control and experimental groups after thepre-test. In addition, interviews were conducted with four students from the experi-mental group and six students from the control group after the Acids–Bases Con-cept Test. These students were those who gave irrelevant answers and hadmisconceptions in tests. During the interviews, researchers asked the selected stu-dents to explain the reasons for their answers and the interviews were audio-taped.

Procedure

Teaching ‘acids and bases’ in the Turkish curriculum begins with a brief introduc-tion of general properties of acids and bases at the fundamental level (includinggeneral properties of acids and bases, an acid and a base definition based on Arrhe-nius theory, effects of acids and bases on litmus paper, and neutralization) in theeighth-grade science and technology course. Students were taught the extensiveproperties of acids and bases, acid–base theories, strengths of acids and bases, thepH concept, acid–base equilibrium, neutralization, hydrolysis, buffer solutions andtitrations in the 11th-grade chemistry course. This study aimed to investigatewhether active-learning instruction is more effective in teaching the subject of ‘acidsand bases’ in the 11th-grade high-school level (average age of 17 years) than a tea-cher-centered instruction.


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The teacher in the experimental group was trained to implement the instructionbased on active-learning. The teacher and researchers discussed the instructionalplans before implementing the activities. The teacher was required to follow thecontent sequence based on constructivism and ask the strategic questions that wereprepared for construction of knowledge.

Before the instruction, the pre-test was applied to both control and experimentalgroups to identify student prerequisite knowledge about their proficiency for learn-ing ‘acids and bases’. A one-way analysis of variance (ANOVA) was conducted tocompare the scores and the result revealed that there was no significant differencein the mean scores between the groups. A preparatory lesson was conducted to rem-edy students’ lack of knowledge and misconceptions determined according to thepre-test during four class hours in both groups. The experimental group was taughtusing an ‘active-learning’ curriculum developed by the authors and the controlgroup was taught using traditional course content based on teacher-centered instruc-tion. The treatments were continued up to four weeks, five class hours per week bythe same teacher.

Treatment given in the experimental group

Active-learning, as used here, is the implementation of a variety of specific student-centered instructional strategies to teach ‘acids and bases’. It includes experimentalactivities, brain-storming, video presentations, demonstrations, computer animations,and learning together activities that engage active participation of students in learn-ing process (Table 1). The active-learning activities were applied according to con-structivist theory by considering students’, learning difficulties and misconceptionsdetermined in the literature (Bradley and Mosimege 1998; Cros et al. 1986;Nakhleh and Krajcik 1994; Ross and Munby 1991; Schmidt 1991; Sheppard 2006).The active-learning activities were examined by four chemistry educators and fivehigh-school chemistry teachers, and the corrections were made according to theirfeedback. The activities were piloted with a sample of 23 high-school studentsattending one high school and a revision was made according to their feedback.

The main application of active-learning activities was accomplished with theparticipation of 21 high-school students, who were randomly assigned into theircooperative groups (one of them with five students and four of them with four stu-dents) based on their previous semester’s chemistry course scores and their socialabilities determined by the teacher. Before the instruction, the teacher gave an orien-tation lesson to the students about learning objectives, active-learning process, rulesof working in a cooperative group, roles and their responsibilities, and assessmentstrategies (Johnson and Johnson 1989).

While constructing the active-learning activities constructivist learning theorywas considered and it was aimed to improve students’ cognitive and collaborativeskills by creating opportunities for students to explore their ideas, recognize the con-flicts between their existing concepts and scientific concepts, construct the newknowledge by correlating with their existing conceptions, think, share ideas and dis-cuss during the learning process (Caprio 1994; Marek, Eubanks, and Gallaher 1990).According to this, firstly students’ pre-existing knowledge should be determined,because these ideas interfere with the learning process. For this reason, each subjectwas begun with the connection between past and present learning experiences andstudents were required to become mentally engaged in the concepts and process.


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Table1.

The

activ

ities

andlearning

objectives

relatedto

theunit‘acids

andbases’.

Subject

The

activ

ities

Learningobjectives

General

propertiesof

acidsand

bases

Abrain-stormingactiv

ityrelatedto

general

propertiesof

acidsandbases

Areadingpassagerelatedto

thehazardsof

acids

Avideopresentatio

nanddemonstratio

nrelatedto

theaffectsof

acidsandbaseson

litmus

paper

Describethegeneralpropertiesof

acidsandbases

Classifyacidsandbasesdependingon

theirgeneralproperties

Giveexam

pleof

acidsandbasesfrom

thedaily

life

Explain

theaffectsof

acidsandbaseson

thelitmus

paper

Acidandbase

theories

Arrhenius

theory

Bronsted–Low

rytheory

Formationof

hydronium

ion

Bronsted–Low

ryacid

base

andconjugated

pairs

Alearning

together

activ

ityandcomputer

anim

ations

relatedto

Arrhenius

andBron-

sted–L

owry

acid

andbase

theories.

Group

studyandcomputeranim

ationrelated

toidentifi

catio

nconjugated

acid

andbase

pairs

Class

discussion

aboutcomparisonof

Arrhe-

nius

andBronsted–

Low

ryacid–b

asetheories

Explain

Arrhenius

acid

andbase

theory

Recognize

Arrhenius

acidsandbases

Explain

thelim

itatio

nsof

Arrhenius

acid

andbase

theory

Explain

Bronsted–Low

ryacid

andbase

theory

Recognize

Bronsted–Low

ryacidsandbases

Describeform

ationof

hydronium

ion

Identifyam

photer

substanceandtherole

ofwater

Recognize

conjugated

acid–basepairs

Com

pare

Arrhenius

andBronsted–Low

ryacid–basetheories

Ionizatio

nof

water


ityrelatedto

ionizatio

nof

water

Alearning

together

activ

ityrelatedto

the

variations

ofH3O+andOH–ionconcentration

inthepure

water

byadding

acidsor

bases

andchanging

water

ionizatio

nconstant

depend

ontemperature

Explain

ionizatio

nof

water

Write

theionizatio

nconstant

ofwater

Com

menton

thevariations

ofH3O+andOH–ionconcentra-

tiondependingon

additio

nalacid

orbase

Explain

thereason

ofchanging

water

ionizatio

nconstant

depend

ontemperature

(Contin

ued)


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Tab

le1

(Contin

ued)

Subject

The

activ

ities

Learningobjectives

pHandpO

HGroup

discussion

relatedto

computin

gpH

andpO

Hof

asolutio

nA

brain-stormingactiv

ityrelatedto

the

variations

ofpH

andpO

Hby

adding

acid

orbasesto

pure

water

Define

pHandpO

H

Explain

therelatio

nsbetweenpH

/pOH

andH3O+/OH–ion

concentrations

Explain

thevariations

ofH3O+andOH–ionconcentrationby

adding

acid/baseaccordingto

LeChatelierprinciple

Com

pute

theH3O+andOH–ionconcentrations

inasolutio

nPredict

theacidic,basicor

neutralpropertiesof

asolutio

ndependingon

pHandpO

HMeasurementof

pHand

indicators

Indicators

pHmeter

Ademonstratio

nrelatedto

identifi

catio

nof

acidic

orbasicpropertiesof

asolutio

nby

usingindicators

Agroupdiscussion

aboutworking

principles

ofindicators

Avideopresentatio

naboutpH

andneutral

indicators

Anexperimentalactiv

ityrelatedto

indicators

Explain

theim

portance

ofmeasuring

pHof

asolutio

nExplain

thepH

measurementmethods

Describeindicators

Explain

thebehaviourof

anindicatorin

anacidic

orbasic

medium

Predict

theacidic

orbasicpropertiesof

asolutio

ndepend

oncolour

change

ofan

indicator

Describenaturalindicators

Explain

thenecessity

ofusingpH

meters

Strengths

ofacid

andbase

Strong–

weakacids

Strong–

weakbases

The

relatio

nsam

ong

Ka,KbandKw

Alearning

together

activ

ityrelatedto

strong

andweakacidsandbases

Describestrong

acid

andbase

Describeweakacid

andbase

Com

pare

strengthsof

acidsor

basesdependingon

their

molecular

structure

Write

ionizatio

nconstantsof

weakacids/bases

Predict

thestrengthsof

acidsor

basesdepend

ontheir

ionizatio

nconstants.

Explain

therelatio

nsam

ongKa,KbandKw

Define

strong

andconcentrated

acidsandbases

(Contin

ued)


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Tab

le1

(Contin

ued)

Subject

The

activ

ities

Learningobjectives

Moleculestructureand

acid–basebehaviour

The

factorsof

affectingthe

acidsandbasesstrengths

Oxyacids

Alearning

together

activ

ityrelatedto

the

factorsaffectingthestrengthsof

acidsand

bases

Alearning

together

activ

ityrelatedto

the

factorsthat

determ

ineacidic,basicand

amphoteric

behaviourof

molecules

inthe

structureof

Y–O

–HA

learning

together

activ

ityrelatedto

the

basicbehaviourof

metalsandmetal

oxides

andacidic

behaviours

ofnon-metal

oxides

Explain

therelatio

nsbetweenacid

strength

andthevariations

ofelectronegativity

andsize

ofan

atom

Describeoxyacids

Explain

thereason

foracidic

orbasicbehaviourof

amolecule

inthestructureof

Y–O

–HExplain

thefactorsaffectingof

thestrengthsof

oxyacids

Write

thereactio

nof

activ

emetalsin

thewater

medium

Write

thereactio

nof

non-metal

oxides

inthewater

medium

Determineam

photer

oxide

Classifymetal,non-metal

andam

photer

oxides

Reactions

ofacid

andbase

Reactions

ofacids

Reactions

ofbases

Twovideopresentatio

nsrelatedto

the

reactio

nsof

acidswith

activ

emetals


ityrelatedto

the

reactio

nsof

acidswith

amphoter

metals

Anexperimentalactiv

ityrelatedto

the

reactio

nsof

acidswith

metals

Ademonstratio

nrelatedto

thereactio

nsof

acidswith

carbonates

Twocomputeranim

ations

relatedto

the

reactio

nsof

baseswith

amphoter

metals

Write

thereactio

nsof

activ

emetalsandacids

Explain

thereason

ofthereactio

nsof

noblemetalswith

HNO3andH2SO4that

includeoxygen

Write

thereactio

nsof

metal

oxides

andacids

Com

menton

thereactio

nbetweenacidsandcarbonates

Write

thereactio

nsbetweenam

photer

metalsandacid/bases

Explain

form

ationof

soap

asaresultof

thereactio

nof

bases

with

oilacids

Lew

isacid

andbase

Twocomputeranim

ations

relatedto

Lew

isacidsandbases

Explain

Lew

isacid–basetheory

Calculatio

nof

pH–p

OH

ofweakacid

andbases

Calculatio

nof

pHof

weak

acidsandions

concentration

Calculatio

nof

pHof

weak

basesandions

concentration

Group

studyrelatedto

writin

gtheequatio

nsof

KaandKbionizatio

nconstants.

Group

studyrelatedto

calculationof

pH,

pOH

andionconcentrationof

weakacid

and

base

solutio

ns

Calculate

thepH

/pOH

ofstrong

acid/basesolutio

nsWrite

theequatio

nsof

KaandKbionizatio

nconstants

Calculate

pH,pO

H,H3O+andOH–concentrationof

weak

acid/basesolutio

ns

(Contin

ued)


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Tab

le1(Contin

ued)

Subject

The

activ

ities

Learningobjectives

Neutralizationreactio

nsA

brain-stormingactiv

ityrelatedto

neutraliza-

tionreactio

nsTw

ocomputeranim

ations

relatedto

neutral-

izations

ofstrong

acid

with

strong

base

and

strong

acid

with

weakbase

Explain

neutralization

Write

theneutralizationreactio

nsof

acidsandbases

Explain

partialandcompletelyneutralization

Predict

theneutralizationproduct

Explain

thevariations

ofpH

ofasolutio

naftertheneutraliza-

tion

Calculate

thepH

ofasolutio

nafterneutralization

Hydrolysisreactio

nsHydrolysisof

acidic

salts

Hydrolysisof

basicsalts

Hydrolysisof

salts

ofweak

acidsandbases

Alearning

together

activ

ityrelatedto

hydro-

lysisof

salts

indifferentproperties

Explain

hydrolysis

Predict

thebehaviourof

thesaltas

aproductof

neutralization

depend

ofthepropertiesof

acid

andbase

Explain

thereason

ofhydrolysisof

acidic

andbasicsalts

Buffers

Abrain-stormingaboutbuffer

system

sin

daily

life

Alearning

together

activ

ityrelatedto

buffer

solutio

nsA

groupstudyrelatedto

computin

gpH

ofbuffer

solutio

nsA

readingpassageaboutthebuffer

system

inhuman

blood

Define

buffer

solutio

nsPredict

buffer

solutio

nsCalculate

pHof

buffer

solutio

nsGivesomebuffer

exam

ples

from

daily

life

Titrations

Titrationcurves

Strongacid–strongbase

titratio

nsStrongacid/base–weakbase/

acid

titratio

ns

Acomputeranim

ationrelatedto

acid–b

ase

titratio

nGroup

studyrelatedto

identifi

catio

nof

equiv-

alence

points,variations

ofpH

,pO

Handion

concentrationduring

titratio

nAnexperimentalactiv

ityrelatedto

strong

acid

andstrong

base

titratio

n

Describetitratio

nExplain

theim

portance

oftitratio

nin

thedaily

life

Define

analyteandtitrant

Define

equivalenceandendpoints

Explain

theprocedures

ofusingindicatorduring

thetitratio

nCalculate

pHof

thesolutio

nduring

thetitratio

nPlotthestrong

acid–strongbase

titratio

ncurve


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In this stage, generally brain-storming, computer animations, group discussions,demonstrations were used. In the second stage, the aim was actively to involve stu-dents in the learning subject as they work together in their cooperative groups.Through new experiences, the aim was to develop students’ deeper and broaderunderstanding of major concepts, obtain more information about areas of interest,and refine their skills. The active-learning activities can be seen in Table 1 in moredetail.

Treatment given in the control group

In teacher-centered instruction, learning focuses on the mastery of content, with lit-tle development of the skills and attitudes necessary for scientific inquiry. The tea-cher transmits information to students, who receive and memorize it. Assessmentsof knowledge typically involve one right answer. The curriculum is loaded withmany facts and a large number of vocabulary words, which encourages a lectureformat of teaching (Leonard and Chandler 2003).

In this study, students in the control group were instructed via teacher-centereddidactic lecture format. During this process, the teacher presented the same contentas the experimental group and the aim was to enhance students the same the learn-ing objectives. The students were instructed with regular chemistry textbooks. Theylistened to the teacher carefully, took notes and solved algorithmic problems.

Results

In order to identify students’ prior knowledge of ‘acids and bases’, the pre-test wasadministered to both control and experimental groups. A one-way ANOVA wasconducted to compare the mean scores of experimental and control groups. As seenin Table 2, it was found that the mean scores of control and experimental groupswere 40.14 and 41.92, respectively. The analysis results also expressed that therewas no statistically significant difference among the control and experimentalgroups in terms of pre-test mean scores (F1,43 = 2.66, p > 0.05; Table 3).

Based on students’ pre-tests scores, semi-structured interviews were conductedwith five students from two groups. Interviews were conducted individually, each

Table 2. Mean scores of experimental and control groups in pre-test.

Group n Mean Standard deviation Standard error

Experimental group 21 40.14 3.69 0.81Control group 24 41.92 3.60 0.73Total 45 41.09 3.71 0.55

Table 3. ANOVA results of the pre-test.

Sum of squares df Mean of squares F p

Between groups 35.240 1 35.240 2.66 0.11Within groups 570.405 43 13.265Total 605.644 44


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lasting approximately 15 minutes in order to explore the reasons behind their pre-test answers. The pre-test and interviews results indicated that students held somemisconceptions about some subjects which were also the prerequisite knowledge forlearning ‘acids and bases’ such as the periodic table, electronegativity, chemicalbonding, inter-molecular forces, and chemical equilibrium. It was determined thatstudents commonly perceive H as a metal; define HCl as an ionic compound;explain hydrogen bonding between H and F, O, or N atoms inside a molecule. Stu-dents’ answers underlined that although they commonly explained ionizationenergy, electron affinity and electronegativity correctly, they could not interpret thereason of their variations in the periodic table. It was also found that students haddifficulties in explaining Le Chatelier principle and relationship between chemicalequilibrium and reaction rate.

In order to identify students’ understanding of ‘acids and bases’, the achieve-ment test was applied after the implementation. The mean scores of both controland experimental groups were compared by conducting a one-way ANOVA. Themean scores of the experimental and control groups were found as 80.76 and47.83, respectively. The ANOVA results showed there was a statistically significantdifference between groups (F1,43 = 102.53, p < 0.05, Table 4 and Table 5).

Based on the Acids–Bases Concept Test results, 15-minute individual interviewswith four students from the experimental group and six students from the controlgroup were conducted. During the interviews, students were asked to explain theiranswers to the items in the achievement test. For example, Item 15 was related toneutralization concepts. Some sample interview sections between researcher (R) anda student (S) are given below:

R:Your answer to the item 15 is ‘The neutralization reaction of an acid with a basewill always produce a salt with the pH of 7’. Could you give me more details aboutyour answer?

S1: Yes. Neutralization reaction is asked in this question. If neutralization occurs, theproduct is a salt and its pH is 7, because the solution is neutral.

Table 4. Mean scores of experimental and control groups in the achievement test.

Group n Mean Standard deviation Standard error

Experimental group 21 80.76 12.21 2.66Control group 24 47.83 9.58 1.95Total 45 63.20 19.79 2.95

Table 5. ANOVA results of the achievement test.

Sum of squares df Mean of squares F p

Between groups 12144.057 1 12144.057 102.53 < 0.001Within groups 5093.143 43 118.445Total 17237.200 44


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R: Why do you think like that? Is the solution always neutral?

S1: Yes. Always. . . The neutralization reaction is eliminating the properties of strongacids and strong bases.

R: Is there any neutralization reaction between a strong acid and a weak base?

S1: No.

R: Why?

S1: Because there is a strong acid in the solution. A strong acid can eliminate theeffect of a weak base. But... A weak base could not eliminate the acidic properties ofa strong acid. So... The solution isn’t neutral. It is an acidic.

R: Can you define what a neutralization reaction is?

S1: Neutralization is a reaction in which a strong acid and a strong base react witheach other to produce a neutral salt solution.

R: Do you mean only a strong acid and a strong base neutralize each other? Is itright?

S1: Certainly... Yes... If any of them is weak, the reaction isn’t neutralization.

R: Hi S2. I would like to interview with you about your answers to the concept test.It was identified that your answer to the item 20 is ‘Strong acids are always concen-trated’. Could you give me more details about your answer?

S2: Yes of course. A strong acid ionizes completely in an aqueous solution. So theconcentration of hydronium increases. Thus it is concentrated.

R: How can you define concentrated solution and dilute solution?

S2: If a solution is concentrated, it has more solute. If it is dilute, the amount of soluteis less than solvent.

R: As you know HCl is a strong acid. In this situation, can you compare 6 M HClsolution and 1 M HCl solution? Are both of them concentrated solution?

S2: Yes. Because HCl ionizes completely in both solutions. This means the solutionsare concentrated.

R: Ok. If the acid was not strong? I mean what can you say about 1 M HF and 6 MHF solutions?

S2: All right. HF is weak acid. And it ionizes incompletely. . . So its ionization couldnot be changed. We can add more or less weak acid to the water. But its ionizationwill be the same. Because of its equilibrium. Because it ionizes incompletely it will bedilute solution all the time.

Based on the findings obtained from the achievement test and interviews, it wasfound that the experimental group students had fewer misconceptions and under-stood the concepts more meaningfully than students in the control group. In thisstudy, 54 misconceptions, 14 of them not reported in the literature before, wereobserved. These misconceptions were classified under the subheadings of; ‘acid and


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base theories’; ‘metal and non-metal oxides’; ‘acid and base strengths’; ‘neutraliza-tion’; ‘pH and pOH’; ‘hydrolysis’; ‘acid–base equilibrium’; ‘buffers’; ‘indicator’;‘titration’ (Table 6).

As seen in Figure 1, 74% of the 54 misconceptions held by the control groupstudents were repeated by 20–50% of students. On the other hand, it was deter-mined that the experimental group students had 21 misconceptions, of which 18were repeated in the ratio of approximately 5%.

Discussion

The present study was an investigation of the effectiveness of active-learning –which includes a variety of specific student-centered instructional strategies such asexperimental activities, brain-storming, video presentations, demonstrations, com-puter animations, and learning together activities – on high-school students’ under-standing of ‘acids and bases’.

Active-learning provides students with opportunities to engage in higher-orderthinking skills and in processes of shared thinking, which help them to not onlygain a better understanding, but also to build on their contributions to develop newunderstandings and knowledge (Brown 1992). As mentioned by Ausubel (1968),students’ prior knowledge is the most effective factor that influences their learningand students construct their knowledge by correlating it with existing concepts. Thecauses of student difficulties in acid–base chemistry have been ascribed to the exis-tence of many misconceptions and a poor understanding of the particulate nature ofmatter, solubility, ionic dissociation of substances and chemical bonding(Furió-Más, Calatayud and Bárcenas 2007; Nakhleh and Kracjik 1993; Nakhleh1994; Sheppard 2006; Smith and Metz 1996). For this reason, students’ priorknowledge and possible misconceptions should be identified for learning subsequentsubjects with high achievement (Bodner 1986; Garnet, Garnet, and Hackling 1995;Hewson and Hewson 1983; Jonassen 1991). In this study, before the instruction, a

Figure 1. Percentages of experimental and control group students’ misconceptions.


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Table6.

The

percentage

ofstudents’misconceptio

nsaboutacidsandbases.

Misconceptio

nsaboutacidsandbases

Experim

ental

group(%

)Control

group(%

)

Acids

andbase

theories

Electrons

transfer

from

acidsto

basesin

acid–basereactio

ns.⁄

4.76

20.83

Acids

cannot

benegativ

eandpositiv

eions

orneutralmolecules.

0.00

25.00

Acids

arethesubstances

that

only

includeH+andbasesarethesubstances

that

only

includeOH–.

0.00

33.33

Because

water

iscovalent

molecule,

itcannotionize.

0.00

41.67

Metal

andnon-metal

oxides

Allthenon-metal

oxides

have

acidic

properties.⁄

0.00

20.83

The

basicpropertiesof

metal

oxides

reduce

from

topto

botto

min

agroupin

periodic

table.

0.00

12.50

The

compounds

ofelem

entswith

high

electronegativity

andoxygen

have

basicproperties.⁄

0.00

8.33

Acidicpropertiesof

oxides

increase

from

topto

botto

min

agroupin

periodic

table.

0.00

8.33

Strengthof

acidsandbases

While

numberof

Hincreasesin

amolecule,

itsacidity

increases.

4.76

29.17

Strongacidsarealwaysconcentrated.

4.76

25.00

While

thestrength

ofan

acid

increases,its

molar

concentrationalso

increases.⁄

0.00

4.17

While

adilutedsolutio

nof

anacid

isweak,

itsconcentrated

solutio

nisstrong.⁄

4.76

25.00

The

strength

ofan

acid

orbase

isrelatedto

itselectronegativity

orsize.⁄

0.00

4.17

The

reason

ofincreasing

acid

strength

throughout

agroupisdecreasing

electronegativity

ofatom

s.⁄

0.00

16.67

Neutralization

The

pHvalueof

asolutio

nform

edas

aresultof

areactio

nbetweenacid

andbase

with

equalmol

and

volumeisalways7.

0.00

20.83

Neutral

solutio

nsareform

edin

alltheneutralizationreactio

ns.

4.76

25.00

The

pHof

salts

which

areproductsof

acid

andbase

neutralizationreactio

nsisalways7.

4.76

29.17

The

saltsolutio

nsof

strong

acid/baseandweakbase/acidhave

neutralproperties.⁄

4.76

29.17

While

thereactio

nof

astrong

acid

andstrong

base

iscompleteneutralization,

thereactio

nof

aweakacid/base

andstrong

base/acidispartialneutralization.

⁄4.76

16.67

The

solutio

nform

edas

aresultof

neutralizationdoes

notincludeH3O+andOH–ions.

4.76

41.67

Neutral

solutio

nsdo

notincludeOH–andH3O+ions.

4.76

37.50

Ifanysolutio

ndoes

notincludeOH–andH3O+ions,itisneutral

4.76

37.50

Acids

andbasesalwaysdisposetheirproperties.

4.76

33.33

Neutralizationreactio

nsonly

occurbetweenstrong

acidsandstrong

bases.

4.76

29.17

Strongacidscanneutralizeweakbases,butweakbasescannot

neutralizestrong

acids,becauseOH–

ionconcentrations

that

comefrom

basesareless

than

theH3O+ionconcentrations

comefrom

acid.⁄

4.76

37.50

(Contin

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Tab

le6

(Contin

ued)

Misconceptio

nsaboutacidsandbases

Experim

ental

group(%

)Control

group(%

)

Saltisnotproduced

inareactio

nbetweenan

acid

andabase.

9.52

37.50

pH–pOH

While

pHincreases,H3O+ionconcentrationincreases.

0.00

37.50

The

pHvalues

ofstrong

acidsarenear

to7.⁄

0.00

20.83

While

numberof

Hin

amoleculeincreases,thepH

valuedecreases.

0.00

29.17

Ifthestrength

ofan

acid

increases,thepH

valueincreases.

0.00

16.67

Hydrolysis

Allthesaltsolutio

nsareneutral.

9.52

45.83

The

pHof

theNH4Clsolutio

nis7.

0.00

29.17

Saltsonly

ionize

inthewater

andthey

donotreactwith

water.

0.00

8.33

OH–andH3O+ionconcentrations

inasolutio

nof

weakacid

saltareequal.

0.00

12.50

Acidandbase

equilib

rium

Ifweakacid

saltisaddedto

aweakacid

solutio

n,thepH

decreases.

0.00

8.33

Ifastrong

base

isaddedto

aweakacid

solutio

n,thereareonly

OH–ions

inthesolutio

n.0.00

12.50

Acidity

constant

does

notchange

with

temperature.

0.00

29.17

Buffers

Abuffer

isonly

form

edby

aweakacid

andits

salt.

4.76

41.67

Abuffer

isform

edby

anacid

andits

salt,

notits

conjugated

base.

0.00

50.00

Buffers

areneutralsolutio

ns.

0.00

20.83

Buffers

canbe

form

edby

usingHClandNaC

l.0.00

16.67

Buffers

canbe

form

edby

usinganyacid

orbase

solutio

nsandtheirsalts.⁄

0.00

41.67

Indicators

Indicators

arestrong

acids.

0.00

45.83

Indicators

areused

todeterm

inethestrength

ofacidsandbases.⁄

9.52

37.50

Indicators

neutralizeacidsandchange

colour.

4.76

20.83

Titration

Any

indicators

canbe

used

intitratio

n.4.76

29.17

pHisalways7at

theequivalencepoint.

4.76

25.00

Equivalence

pointisthepH

valueat

which

colour

change

occurs.

0.00

25.00

The

volumeof

acid

asan

analyteandbase

asatitrant

isalwaysequalat

theequivalencepoint.⁄

0.00

37.50

Weakbasescannot

titrate

with

weakacids.

0.00

16.67

Note:

⁄ Firstdeterm

ined

misconceptio

nsin

thisstudy.


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pre-test was administrated to both the control and experimental groups to identifytheir prerequisite knowledge about their proficiency for learning the subject. TheANOVA results showed that the mean scores of the control and experimentalgroups were 40.14 and 41.92, respectively, and no statistically significant differencewas found between groups (F1,43 = 2.66, p > 0.05). However, it was found that stu-dents in both groups had some misconceptions about inter- and intra-molecularforces, ionization energy, electron affinity and chemical equilibrium. The obtainedresults indicated that most of the students commonly perceived H as a metal,defined HCl as an ionic compound, explained hydrogen bonding between H and F,O, or N atoms inside a molecule. These misconceptions were also similar to thosereported in the literature (Boo 1998; Coll and Taylor 2001; Coll and Treagust 2001,2002). Students’ answers revealed that although they commonly explained ioniza-tion energy, electron affinity and electronegativity correctly, they could not interpretthe reason of their variations in the periodic table. As mentioned by Gussarsky andGorodetsky (1990), Hackling and Garnett (1985), and Hameed, Hackling, and Gar-nett (1993), students also had difficulties in explaining Le Chatelier principle andcould not interpret the changes in a reaction depending on any impact on a systemin equilibrium. After remediation of the students’ lack of knowledge and miscon-ceptions via a preparatory lesson, the experimental group was taught using anactive-learning and the control group was taught using teacher-centered instruction.Immediately after the instructions the achievement test was administrated to bothgroups to identify their understanding of ‘acids and bases’.

The results showed that active-learning instruction caused significantly betteracquisition of scientific conceptions than the teacher-centered instruction. The meanscores of students in the experimental group and in the control group were found tobe 80.76 and 47.83, respectively. Based on the ANOVA results, there was a statisti-cally significant difference between the control and experimental groups (F1,43 =102.53, p < 0.05). The difference of the mean scores in the experimental group canbe explained by the positive effects of active-learning on students’ understandingsof ‘acids and bases’. On the other hand, students’ responses to the test and thesemi-structured individual interviews showed that the number and percentage ofmisconceptions of the experimental group were significantly fewer than the controlgroup students. According to the results, 54 misconceptions related to acid–basetheories, metal–non-metal oxides, strength of acids and bases, neutralization, pHand pOH, hydrolysis, acid–base equilibrium, buffers, indicators, and titration wereidentified. Of these identified misconceptions, 40 have some similarities with thosein the literature and 14 of them were first identified in the context of this study.These were: ‘electrons are transferred from acids to bases in acid–base reactions’;‘all the non-metal oxides have acidic properties’; ‘the compounds with high electro-negativity and oxygen have basic properties’; ‘while the strength of an acidincreases its molar concentration also increases’; ‘while a diluted solution of an acidis weak, its concentrated solution is strong’; ‘the strength of an acid or base isrelated to its electronegativity or size’; ‘the reason of increasing acid strengththroughout a group is decreasing of electronegativity of atoms’; ‘the salt solutionsof a strong acid/base and a weak base/acid have neutral properties’; ‘while the reac-tion of a strong acid and a strong base is complete neutralization, the reaction of aweak acid/base and a strong base/acid is partial neutralization’; ‘a strong acid canneutralize weak base, but a weak base could not neutralize a strong acid becauseOH– ion concentrations come from base are less than H3O

+ ion concentrations


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come from acid’; ‘the pH values of strong acids are near to 7’; ‘buffers can beformed by using any acid or base solutions and their salts’; ‘indicators are used todetermine the strength of acids and bases’; ‘the volume of an acid as an analyteand a base as a titrant is always equal at the equivalence point’.

The interviews conducted with four students from the experimental group andsix students from the control group after the achievement test gave detailed infor-mation about the reasons for obtained misconceptions. Students’ responses reflectedthat misconceptions related to acid–base theories generally related to having diffi-culties with the use of different models in acid–base chemistry, as indicated in theprevious studies by Schmidt (1995), Vidyapati and Seetharamappa (1995), andKousathana, Demerouti, and Tsaparlis (2005). Because the chemistry curriculumundertakes the subject of ‘acids and bases’ according to Arrhenius and Bronsted–Lowry theories and the differences between these theories is not explained, stu-dents commonly confused these theories with each other, could not give the correctacid–base samples, and had difficulties in explaining Lewis theory. The causes ofthe misconceptions about metal and non-metal oxides and acid–base strengths weregenerally related to students’ failures on using and integrating their prior knowl-edge about metals, non-metals, the periodic table, ionization energy, atom size,electronegativity, solubility, and inter- and intra-molecular forces. It was alsoobtained that a student who had misconceptions about pH and pOH could notunderstand the logarithmic nature of pH as mentioned by Sheppard (2006). Themisconceptions with high percentages were related to neutralization, hydrolysis,buffers, and indicators. The interviews reflected that the reasons for these miscon-ceptions have close relationship with each other. Students commonly confused theterms ‘neutral’ and ‘neutralization’; therefore, they could not associate the neutral-ization reactions with the concentrations and strengths of acids/bases. This couldalso cause the misconceptions related to hydrolysis and buffers. Additionally, itwas obtained that students who had lack of knowledge and misconceptions relatedto the concepts of chemical equilibrium, solution and neutralization could also notexplain buffers as underlined also by Ross and Munby (1991) and Sheppard(2006).

In the light of these results, while the students in the active-learning classhad few misconceptions about acids and bases, the students taught using tea-cher-centered learning approach had more misconceptions. This situation showsthe power of active-learning treatment based on constructivism in improving stu-dents’ learning achievement, preventing misconceptions, and improving students’higher-order thinking skills such as analysis, making connections, synthesis, andanalytical cognitive thinking in contrast with a teacher-centered approach.

AcknowledgmentThis study was supported by the Scientific and Technological Research Council of Turkey(Project Number: TUB-105K058).

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active-learning versus teacher-centered instruction for learning acids and bases

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