Findings: learners’ responses to the pre-test questions

The learners’ responses to the pre-test questions (Appendix S) are discussed in relation to how learners were expected to answer them. In this sub-section, the learners’ answers are discussed following the questioning order used in the pre-test. Numerical data describing how a number of learners attempted each question were used as additional information revealing learners’ sense-making of the topic.

121 (a) Question 1 (The relationship between the atomic structure and the periodic table) This question tested the learners’ ability to identify the group and the period number of an atom of an unidentified element by analysing its Bohr diagram. This element was sulphur.

Two marks were allocated to this question. Though this question did not test any of the specific objectives on the topic of chemical bonding in the Physical Science syllabus, it was asked because an atomic structure, and its relationship to the periodic table, were described by Gilbert and Treagust (2009) as an introduction to other basic chemistry concepts, such as bonding of elements and molecular/ionic structures of compounds – the topics under focus in this study.

From a total of thirty-eight learners, sixteen could not identify either the group or period number of an element from the Bohr structure drawn. The information that this Bohr structure was for a sulphur atom was not provided, in order to test if they could identify its group and period number by looking at its number of shells the and number of electrons in the outer shell. I noticed that many of them had an incorrect perception of this relationship.

Some interpreted a group number as equal to the number of shells, and a period number as equal to the number of electrons located in the outer shell. Many answered that this atom belongs to an element in group three and in period six. Others answered that the group number of this atom is sixteen. These answers were all incorrect and revealed that these learners had little fundamental knowledge of chemistry, which could be the factor negatively impacting their sense-making of chemical bonding.

(b)Question 2 (The relationship between atoms and molecules and bonding processes) I asked this question to test the learners’ knowledge of an atom-molecule relationship and the activities taking place during the bonding processes. Four marks were allocated to this question. I realised that many learners did not score all the marks for this question, although I considered it not to be challenging.

Question 2(a), 2(b), and 2(c) tested the learners’ ability to distinguish between atoms and molecules. These questions were challenging, as thirty-three learners did not score all the marks allocated for them. Many of them incorrectly referred to a single circle as a molecule and a group of circles joined as an atom. The correct explanation would have been that a single circle represents an atom and a group of circles jointed together represents a molecule.

122 Question 2(d) tested the learners’ knowledge of concepts used in covalent bonding as opposed to ionic bonding. There were four words (atom, molecule, share, and transfer) given for the learners to identify the one that correctly described a covalent bond in a hydrogen oxide (water) molecule. They were expected to choose the concept ‘share’ to describe the overlapped outer shells with electrons contained between them. However, instead of doing this, fifteen of them chose the concept ‘transfer’ – a concept that is only applicable to ionic bonding. A few learners misunderstood this question, as they gave concepts that were not on the list. Some of these words were hydrogen oxide, outer shell electrons, and oxygen. Other learners did not attempt to answer this question. I therefore found that the learners’ low proficiency in English – a Language of Learning and Teaching (LoLT) in Namibian schools – contributed to the problem. Hence, I resolved that addressing this problem may be possible if teaching of chemical bonding is done via the visual mode integrated with the verbal mode for the meaning to be clearer to learners.

(c) Question 3 (Bond type identification)

The learners were provided with a skeletal Bohr structure of a chlorine molecule (Cl2) for them to identify the type of chemical bonding it showed. This structure had visible overlapped shells, which collocate with the lexical item ‘covalent bond’; the answer to this question. Four marks were allocated to this question; however, only five learners earned full marks. Many of them who correctly identified the bond as covalent could not explain their answer correctly. I discovered that they guessed, since they had only learned two types of chemical bonding: covalent and ionic. Nine of them incorrectly reasoned that the protons shared by the two atoms indicate a covalent bond. This showed that they were aware that the concept ‘share’ is applicable to covalent bonding, though they confused protons with electrons.

The second question (Question 3(b)) asked learners to state the side of the zigzag line in a periodic table where this element is located. Fifteen of them answered that it is located on the right side of the periodic table – which is correct. Seven learners were more correct, as they also reasoned that the sharing of electrons only happens between atoms of non-metal elements, which are located on the right side of the periodic table. This showed that more than half of the learners in the class had knowledge of the periodic table following a traditional teaching to chemical bonding. However, some of those who correctly identified the element as located on the right of the zigzag line could neither support their choice nor

123 give explanations that were relevant to the question. It is possible that they guessed and were fortunate that the answer they gave was correct.

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

I set this question to test the learners’ knowledge of charges formed when atoms lose or gain electrons. I allocated three marks to this question. In Question 4(a), a simple Bohr structure of a magnesium atom with two electrons in the outer shell was provided to the learners. They were subsequently asked to identify the charges formed when this atom becomes an ion.

Unfortunately, only seven learners scored full marks on this question. Among the remaining thirty-one learners, only eight correctly identified the charge as positive or wrote a magnesium ion as Mg⁺². Moreover, many of them failed to support their answers. Other learners gave answers that were completely incorrect, while still others did not attempt to answer the question. Therefore I noticed that knowledge of chemical bonding related to charges was not sufficiently accessed by learners, and thus required consideration in the intervention cycle.

In Question 4(b), I tested the learners’ knowledge of the metallic nature of a magnesium atom – they had to decide whether magnesium was a metal or a non-metal element. Sixteen of thirty-one learners managed to correctly classify a magnesium atom as a metal. Many of the remaining learners classified it as a non-metal, while very few learners identified it as a metalloid – both of which are incorrect. Hence, this demonstrated that learners did not master knowledge of using the periodic table, which includes classifying elements as either metals or non-metals.

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

This question was set to explore the learners’ knowledge of ionic bonding. This knowledge was represented via the visual mode in the form of a bond diagram of sodium fluoride. Two marks were allocated to this question. Twenty-eight learners did not score full marks for this question, revealing that their sense-making of ionic bond knowledge was inadequate.

Question 5(a) required learners to identify a feature on the diagram that showed that the bond in sodium fluoride is ionic. Though there were many features on this diagram revealing that the bond is ionic, the most identifiable one was an arrow pointing from a sodium atom to a fluorine atom. This arrow is similar to the lexical item ‘transfer’, which is only applicable to

124 ionic bonding. Many learners gave incorrect answers to this question. Some of these include one proton transferred, sodium fluoride, compound, and covalent bonding. A few learners did not attempt to answer this question. I realised that many of these answers were incorrect due to using the word ‘feature’, which some learners did not know. This resulted in them giving answers that were not related or relevant to the question.

Question 5(b) tested learners’ knowledge of bond strength in ionic compounds. Learners who scored full marks explained that opposite charges between sodium and fluorine ions create an electrostatic attractive force, which results in a strong bond formation. However, many learners gave wrong answers, such as ‘transferred electrons’ and ‘atom losing protons’. These answers are incorrect, as the transfer of electrons does not directly explain bond strength, even though they have a causal relationship. This relationship involves electrons being transferred from an atom of a metallic element to that of a non-metallic element; changing it from being a neutral atom to a positively charged ion due to it having more protons, which are positively charged, than electrons, which are negatively charged. Some learners did not attempt to answer this question. The two arrows on the bond diagram, one showing a transferred electron and one showing an electrostatic attraction between the two ions, did not make sense to them. Possibly, the word ‘transfer’ should have been written alongside a one- way arrow to further indicate that an electron is transferred from a sodium atom to a chlorine atom – a feature that indicates ionic bonding. This suggested for this intervention that caption is another form of visual and verbal modes combined that would be helpful in addressing this learning difficulty.

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

I formulated this question to test the learners’ sense-making of chemical knowledge related to ions, and names and formulae of ionic compounds. It included a diagram of a sodium atom transferring one electron to a chlorine atom. I allocated four marks to this, and found that twenty-seven learners failed to score full marks.

Even though it was explained that cations are atoms that have lost electrons while anions are atoms that have gained electrons, nineteen learners could not correctly state the type of ion formed by a sodium atom when it loses one valence electron. Nineteen learners correctly mentioned that sodium atoms form cations, but they did not support their answers. This showed that they guessed this answer. However, when asked to write down the name of a

125 compound formed from the reaction between sodium and chlorine, thirty learners wrote

‘sodium chloride’ – which is a correct answer. This shows that most learners have no problem deducing names of compounds from the given names of the reactants. However, I found that twenty-six learners had difficulty writing correct formulae of ionic compounds formed when elements react. Some of the incorrect formulae of sodium chloride written by these learners include NaCl2, H2O, Na2Cl2, Na2Cl, and Na. The correct formula for this compound is NaCl. This is because the net electrical charge of ions in this compound is 0.

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

This question had two Bohr diagrams, one for a covalent bond in hydrogen chloride, and another for an ionic bond in sodium oxide. Question 7 (a) explored learners’ abilities to distinguish between the bond types, with reference to outer shell electrons and bond strength.

Four marks were allocated to this question, and twenty-one learners scored full marks.

Twenty-two learners correctly stated that electrons in hydrogen chloride are shared, while in sodium oxide they are transferred. On bond strength, thirty-two learners correctly described the bond in hydrogen chloride as weak, and in sodium oxide as strong. However, when asked to complete the bond diagram in sodium oxide, fifteen learners failed to do so correctly. Even though more learners distinguished between covalent and ionic bonding correctly, the fact that they struggled to correctly illustrate the bond in sodium oxide means that their chemical knowledge was inadequate.