The Effect of Supplementing Instruction with Conceptual Change Texts on Students’ Conceptions of Electrochemical Cells

Abstract

The aim of this study was to investigate the effectiveness of instruction supplemented by conceptual change texts (CCTs) over traditional instruction on students’ understanding of electrochemical (galvanic and electrolytic) cell concepts. The participants of the study consisted of 64 students from the two classes of a high school located in Turkey. Classes were randomly assigned to experimental group, which was exposed to CCTs as a supplementary material, and to control group, which was exposed to traditional instruction. A 23-item multiple-choice test was developed assess students’ conceptual understanding of electrochemical cells. This test was administered to both groups before and after the instruction. The results of ANCOVA indicated that students who were instructed by using CCTs had better conceptual understanding of electrochemical cells than those experiencing traditional instruction when their prior electrochemical cell concepts understanding was statistically controlled. The findings of this study suggest that CCTs can be used as a cost- and resource-effective supplement to classroom instruction to promote students’ understanding science concepts.

Appendices

Appendix A

Examples of the Electrochemical Cell Concepts Test

• 4. In a galvanic cell constructed by Ni and Ag electrodes, Ni electrode is anode and Ag electrode is cathode. Which one of the following statements is TRUE about the charges of the electrodes of this cell?

  • (a) Ni electrode is negatively charged because it releases electrons.

  • (b) The positive sign of the Ag electrode indicates that Ag has higher reduction potential.

  • (c) Ag electrode is negatively charged because it attracts electrons.

  • (d) Ni electrode is positively charged because it attracts negatively charged anions.

• 6. Which one of the following statements is CORRECT about the standard reduction potentials?

  • (a) Standard reduction potentials can be measured independently without the use of other half- cell reactions with the known potentials.

  • (b) Half-cell reactions with the positive standard reduction potentials are spontaneous.

  • (c) All standard reduction potentials are measured relative to the standard hydrogen electrode.

  • (d) The metal which has the most positive standard reduction potential is the most reactive.

• 15. In an electrochemical cell, conduction through the electrolyte is due to:

  • (a) electrons moving through the solution attached to the ions.

  • (b) the movement of negative ions.

  • (c) electrons moving through the solution from one electrode to the other.

  • (d) the movement of both positive and negative ions.

• 16.

  

  $$ {\text{Ag}}^{{\text{ + }}} {\text{(aq) + e}}^{{{-}}} \to {\text{ Ag(s),}}\quad {\text{ E}}^{{\text{o}}} {\text{ = + 0}}{\text{.80 V}} $$
  $$ {\text{Ni}}^{{{\text{2 + }}}} {\text{(aq) + 2e}}^{{{ - }}} {\text{ }} \to {\text{Ni(s),}}\quad {\text{ E}}^{{\text{o}}} {{ = {\text {-}}0}}{\text{.24 V}} $$

  In the electrochemical cell drawn above, electrons in the cell flow through the _____ toward the _______.

  • (a) wire, silver electrode

  • (b) wire, nickel electrode

  • (c) wire, silver electrode and salt bridge, nickel electrode

  • (d) wire, nickel electrode and salt bridge, silver electrode

• 18. The function of a salt bridge in an electrochemical cell is to:

  • (a) form complex ions with the oxidation products.

  • (b) permit electrons to flow through the solution.

  • (c) keep the levels of liquids equal in both half-cells.

  • (d) allow positive and negative ions to enter and leave both half-cells.

• 19.

  

  What are the products at the anode and cathode in the above electrolytic cell? (Al³⁺, H₂O, Br₂, O₂ are arranged in the order of increasing standard reduction potentials in the following way:

  $$ {\text{Al}}^{{{\text{3 + }}}} {\text{ $ < $ H}}_{{\text{2}}} {\text{O $ < $ Br}}_{{\text{2}}} {\text{ $ < $ O}}_{{\text{2}}} {\text{)}}{\text{.}} $$

  Anode	Cathode
  (a) HBr	Al2O3
  (b) Br2	H2
  (c) Br2	Al
  (d) O2	Al

• 20.

  

  Evaluate the following assertion and reason listed below:

  Assertion	Reason
  If the salt bridge in the picture above was replaced by a copper wire (an electrical conductor), the light bulb would be lit.	...there will be a continuous flow of electrons in the electrolyte solutions that can pass through the copper bridge.
  (a) Both the assertion and the reason are correct.
  (b) The assertion is correct, but the reason is incorrect.
  (c) The assertion is incorrect, but the reason is correct.
  (d) Both the assertion and the reason are incorrect.

• 22. Which drawing best describes the current flow occurring at the salt bridge in the Pb(NO₃)₂ solution?

  

• 23.

  

  $$ {\text{Pb}}^{{{\text{2 + }}}} {\text{(aq) + 2e}}^{{\text{ - }}} {\text{ }} \to {\text{ Pb,}}\quad {\text{ E}}^{{\text{o}}} {\text{ = {\text {-}} 0}}{\text{.12 V}} $$
  $$ {\text{Zn}}^{{{\text{2 + }}}} {\text{(aq) + 2e}}^{{\text{ - }}} {\text{ }} \to {\text{ Zn,}}\quad {\text{ E}}^{{\text{o}}} {\text{ = {\text {-}}0}}{\text{.76 V}} $$

  What is the cell potential for the above electrolytic cell? (a) +0.88 V (b) −0.88 V (c) +0.64 V (d) −0.64 V

Appendix B

Understanding the Current Flow in Galvanic and Electrolytic Cells

$$ {\text{Ag}}^{{\text{ + }}} {\text{(aq) + e }} \to {\text{Ag (s),}}\quad {\text{ E}}^{{\text{o}}} {\text{ = + 0}}{\text{.80 V}} $$

$$ {\text{Cu}}^{{{\text{2 + }}}} {\text{(aq) + 2e }} \to {\text{ Cu(s),}}\quad {\text{ E}}^{{\text{o}}} {\text{ = + 0}}{\text{.34 V}} $$

Before reading the text below, write your answer for the above questions and your reasons in the empty space provided below. If your answer is not correct you may have misconceptions. In that case read the text more than once.

Misconception About Understanding the Current Flow in Galvanic Cells