Findings: learners’ responses to the post-test questions

In this sub-section, I present the learners’ responses to the post-test questions in terms of whether they indicate sense-making improved or not. I also present how a certain number of learners answered each question in this test. This made the analysis manageable, which successfully led to identification of the influences on learners’ sense-making of the topic inculcated by the intervention. The change in the number of learners correctly answering each question in the post-test in comparison to the pre-test indicated the influences of an intersemiotic complementarity teaching approach on learners’ sense-making of the topic.

(a) Question 1 (The relationship between the atomic structure and the periodic table) I set this question to test the learners’ ability to identify the group and period numbers of atoms of unidentified elements from their Bohr diagrams. This is knowledge of the periodic table in relation to an atomic structure, which is an introduction to basic chemistry concepts. I did this with the Bohr diagram of a nitrogen atom, shown in Figure 17. I allocated two marks to this question.

Figure 17. A Bohr diagram of an atom an unidentified element (provided by the teacher in the post-test)

161 Among thirty-eight learners who answered this question, only five could not correctly identify either the group or the period number of this element. Learner M, one of the five learners, did not score any mark due to interchangeably identifying groups and periods.

Thirty-three learners scored full marks for this question. This was astonishing, because only twenty-two learners scored full marks for a similar question in the pre-test. This indicated that the learners’ fundamental knowledge of the relationship between an atomic structure and the periodic table improved substantially during Cycle 2. Moreover, the sense-making type involved in accessing this knowledge was chemical bonding facts – learners making sense of abstract objects and processes of chemical knowledge – which is more aligned to science.

This knowledge is sub-microscopic as it concerns microscopic entities of matter, and therefore learners being conversant with it after Cycle 2 were an indication of improved sense-making of the topic.

(b)Question 2 (The relationship between atoms, molecules, and the bonding process) This question was set to test the learners’ knowledge of the atom-molecule relationship and the bonding process. Answering this question was guided by the simplified Bohr diagram of the covalent bond in a carbon dioxide molecule, as shown in Figure 18.

Figure 18. A Bohr diagram of a carbon dioxide molecule (Taken from the post-test) I allocated three marks to this question. Among thirty-eight learners, three scored full marks for this question, thirty-one scored either two or one, and four did not score any marks.

Comparing the learners’ performance on this question to the similar question asked in the pre-test revealed a slight improvement, as the number of learners scoring full marks increased from zero to three.

162 I set Questions 2(a), (b), and (c) to test the learners’ ability to distinguish between atoms and molecules. Even though only three learners scored full marks for this question, many learners managed to distinguish between atoms and molecules. They identified the circles labelled O and C as representing atoms of elements, and the combination of these circles as representing a molecule. This reveals a slight improvement in the learners’ knowledge of the relationship between atoms and molecules, because many learners had difficulty doing the same in the pre-test. Knowledge of the relationship between atoms and molecules is also sub- microscopic, as it concerns microscopic particles that are non-observable and difficult to understand (Johnstone, 1982). The sense-making type involved in accessing this knowledge is chemical bonding facts, because atoms and molecules are abstract entities of chemical bonding. This reveals that the learners’ sense-making of chemical bonding facts was better in Cycle 2 than in Cycle 1.

(c) Question 3 (Bond type identification)

This question was set to investigate learners’ ability to identify bond types from bond diagrams. I did this with a fluorine molecule (two fluorine atoms bonded), shown in Figure 19. Learners were also asked to identify the side, whether left or right, of the periodic table where this element is located. Four marks were allocated to this question.

Figure 19. A bond diagram of a fluorine molecule (Taken from the post-test)

The visual-verbal intersemiotic complementarity was incorporated in the diagram in the form of visible overlapped shells, which collocated with ‘covalent bond’ as a lexical item.

Moreover, the visible pair of electrons in the overlap is synonymous with the lexical item

‘share’ (a concept describing covalent bonding). This means that this knowledge was presented to learners in both visual and verbal modes coordinated for them to have a better chance of understanding the question than if it was presented in only one semiotic mode.

163 Remarkably, an improvement was noticed in how the learners answered this question in the post-test compared to how they attempted it in the pre-test. In the pre-test, only four learners scored full marks, while in the post-test, the number of learners who scored full marks rose to sixteen. They correctly stated that the type of chemical bond formed between the two fluorine atoms is covalent, and reasoned that it involved the sharing of electrons. They also identified these two atoms as belonging to an element on the right side of the periodic table, reasoning that all non-metal elements are located on the right side of the periodic table.

Moreover, the number of learners who scored three, or half, of the marks increased from fifteen in the pre-test to eighteen in the post-test. These learners lost either one or two marks for this question, indicating that they mostly understood the knowledge being tested.

Incorrect answers that these learners provided involved ‘protons shared’ instead of ‘electrons shared’, and ‘atoms giving away electrons’ instead of ‘atoms sharing electrons’. However, these errors were fewer in the post-test than in the pre-test. Few learners incorrectly mentioned that the two atoms in a molecule belong to an element found on the left side of the periodic table. The correct location of this element is the left, because it is where all non- metals are located in the periodic table. However, the average learners’ performance on this question showed a substantial improvement in their understanding of covalent bonding. The sense-making of chemical bonding applied by the learners for this knowledge was clarification, where learners clarified the chemical process (Johnstone, 1993), such as the covalent bond in a fluorine molecule. These data reveal that their ability to clarify the sub- microscopic knowledge of covalent bonding was enhanced during Cycle 2.

(d)Question 4 (Determining the charge of ions)

This question assessed the learners’ knowledge of charges formed when atoms lose or gain electrons. Learners were given the Bohr diagram of a sulphur atom. This diagram (Figure 20) shows the number of neutrons, protons, and electrons in a sulphur atom.

Figure 20. A Bohr diagram of a sulphur atom (Taken from the post-test)

164 This question was divided into two sub-questions assessing two knowledge aspects: (a) the charge this atom forms when it becomes an ion, and the reason for the answer given; and (b) the metallic nature of sulphur. The correct answer for the first questions is that the charge is - 2 due to this element having a valency of two (it requires two electrons in order to attain a noble gas structure). The correct answer for the second question is that sulphur is a non-metal element.

I allocated three marks to this question, as I did with the corresponding question in the pre- test. This question was answered more correctly than its corresponding question in the pre- test. Unlike in the pre-test, where only seven learners scored full marks, the post-test had nineteen learners scoring full marks for this question. Seven learners managed to score two thirds of the available marks for this question, which shows that they understood much of the knowledge being tested. However, the number of learners who scored either one mark or no marks was still high – but lower than in the pre-test. Some of the common errors I identified involve some learners referring to a sulphur atom as becoming a cation, and others stating that it has a charge of +2. Other learners explained incorrectly that a sulphur atom loses two electrons to form a charge of +2. Some learners did not even attempt to answer this question.

Despite some missing and incorrect answers, the overall learners’ performance on this question was far better in the post-test than in the pre-test.

(e) Question 5 (Ionic bond and its bond strength)

This question assessed the same knowledge of chemical bonding as its corresponding question (Question 5) in the pre-test. I set this question to explore ionic bonding knowledge.

In the pre-test, the learners were provided with the Bohr diagram of the bond between sodium and fluorine, while in the post-test, they were provided with the Bohr diagram of the bond between calcium and oxygen. The slight difference between these two questions was that the bond between sodium and fluorine only involves one electron being transferred, while the bond between calcium and oxygen involves two electrons being transferred. This question was presented via the coordinated visual and verbal semiotic modes, using the sense relations of similarity and collocation. Figure 21 shows this Bohr diagram of the bond between calcium and oxygen atoms.

165

Figure 21. A Bohr diagram of the bond between calcium and oxygen atoms (Taken from the post-test)

This question was divided into two sub-questions [5(a) and 5(b)] that totalled two marks.

Question 5(a) asked learners to identify a feature on the diagram that showed that the bond is ionic. The two electrons indicated by crosses in an oxygen ion collocates with the lexical items ‘calcium lost electrons’ and ‘oxygen gained electrons’, which is only applicable to ionic bonding. I expected these learners to mention electrons lost or gained, opposite charges formed, and the bond involving a metal and a non-metal. The visible structural diagrams of calcium and oxygen ions were similar to ‘metal and non-metal atoms bonded together’, to remind learners that the bond is ionic. The charges also indicated that the bond was ionic, as this is the only bond where both positive and negative ions are formed. Question 5(b) asked learners to identify the feature on the diagram that shows that the bond in calcium oxide is strong. The visible signs of the positive and negative charges collocated with the lexical item

‘strong forces of attraction’. Learners’ explanation of the bond strength in ionic substances revealed that their sense-making via clarifying was enhanced, since they were able to clarify sub-microscopic knowledge of ionic bonding, which is often a challenge to many learners, as Johnstone (1982) suggests.

The number of learners who did not score full marks for this question decreased from twenty- eight in the pre-test to twenty-one in the post-test, and the number of learners who did not score any marks, either because of giving an incorrect answer or not answering the question, decreased from seventeen to nine. This indicated that their sense-making of the knowledge tested improved. Despite this improvement, some learning difficulties on this knowledge persisted. I noticed this as several learners stated that the bond in calcium oxide is ionic because all shells are now full. This reasoning is incorrect, as a bond type is not determined by whether outer shells are full or not, but rather by the metallic nature of elements bonded.

Other learners stated that the bond in calcium oxide is strong since calcium oxide does not

166 dissolve in water easily. This answer is also incorrect because the bond strength is determined by opposite charges between ions of the bonded elements, not by the solubility of a substance.

Overall, I noticed from the findings above that there was a substantial improvement between Cycle 1 and Cycle 2 in terms of how learners make sense of ionic bonding and bond strength in ionic compounds. This indicated to me that many learners could make links between this macroscopic phenomenon (the bond between metals and non-metals), and its sub- microscopic model (the electron transfer process), as mentioned by Gilbert and Treagust (2009). The fact that many learners could explain ionic bonding by referring to electron transfer and the electrostatic attractive force between the oppositely charged ions testified that their ability to use sub-microscopic knowledge (rather than using only their macroscopic knowledge) to elaborate on chemical knowledge was improved.

(f) Question 6 (Ions, names, and formulae formed in ionic bonding)

Question 6 in the post-test differed slightly from its corresponding question in the pre-test.

While both questions tested learners’ ability to identify ions, write names, and deduce chemical formulae of ionic compounds, the pre-test used sodium chloride as an example, while question 6 in the post-test tested this knowledge with the bond in magnesium fluoride.

The diagram in Figure 22 was drawn to guide learners in answering this question.

Figure 22. A Bohr diagram of the bond between magnesium and fluorine atoms (taken from the post-test)

This question consisted of three sub-questions: Question 6(a), which asked learners to classify a magnesium ion as either an anion or a cation; Question 6(b), which required learners to write down the chemical name of the compound formed; and Question 6(c), which asked the learners to write down the chemical formula of the compound formed. These sub- questions were worth four marks in total. I divided the learners’ performance on this question into three groups: those who scored full marks, those who scored half or three quarters of the

167 total marks, and those who scored one mark or no marks. There were sixteen learners who scored full marks, nineteen learners who scored either half or three quarters of the total marks, and three learners who either scored one mark or no marks. In total, the number of learners who scored marks for this question was thirty-five. This performance was better than in the pre-test, where only twenty-seven learners scored any marks.

The sixteen learners who managed to score all four marks stated that an ion formed by a magnesium atom is a cation. They reasoned that this atom loses two electrons, which are transferred to two fluorine atoms. They also managed to correctly write both the name and formula of the compound formed – the name is magnesium fluoride and the formula is MgF2. This indicated that they had developed an ability to grasp both the sub-microscopic and the symbolic knowledge in the same way they had done with the macroscopic knowledge of chemical bonding. However, learners who did not score all marks for this question revealed that they were unable to access both the sub-microscopic and symbolic levels of representation of chemical knowledge. Several of them stated that a magnesium atom forms an anion. This is incorrect because magnesium is a metal, and atoms of metal elements form cations due to their tendency to lose electrons during a bond. Other learners incorrectly wrote the formula for the compound formed as Mg2F or MgF. This revealed that they did not know how charges are used to deduce formulae of ionic compounds. Nevertheless, the overall learners’ performance on this question demonstrated an improvement in learners’ sense- making of the knowledge of ions, likely as a product of the teaching intervention.

(g) Question 7 (Distinguishing between covalent and ionic bonding)

As in the pre-test, this question was guided by the bond diagrams of two compounds:

ammonia and sodium chloride. The bond in ammonia is covalent, while the bond in sodium chloride is ionic. The above-mentioned diagrams are shown in Figure 23.

(a) (b)

Figure 23. The Bohr diagrams of the bonds in ammonia and sodium chloride (Taken from the post-test)

168 I divided Question 7 into two sub-questions: Question 7(a), which tested the learners’

knowledge of the sharing and transferring of electrons, and the strength of the bond formed;

and Question 7(b), which tested the learners’ knowledge of using the periodic table to draw the ionic bond in sodium chloride. I allocated seven marks to this question.

I found that twenty-one learners managed to score all possible marks for this question. They could therefore correctly explain what happens to the outer shell electrons of the atoms that make up ammonia and those that make up sodium chloride. They also managed to correctly classify the bond in both ammonia and sodium chloride as either strong or weak. This indicated that these learners had no difficulty with the sub-microscopic representation of chemical bonding related to bond strength. Interestingly, all these learners represented the ionic bond between magnesium and fluorine in Question 6 correctly.

Among learners who did not score all the marks were those who managed to get half of the marks and above. This was true of nine learners in total; however, these learners also demonstrated that their sense-making of the knowledge had improved. Many of them scored six marks – they were therefore close to scoring all marks available. Interestingly, these learners managed to explain correctly the bond in an ammonia molecule as involving electron sharing, and in sodium chloride as involving electron transfer. Even though a few misconceptions were identified, such as ammonia gaining three electrons and seven protons in outer shells, the learners’ performance on this question in the post-test was remarkably better than their performance in the pre-test.