Chemistry is a very difficult subject. The complexity of Chemistry has implications for the teaching of Chemistry today. From my experience, many students face difficulties in understanding chemical bonding and drawing dot and cross diagrams. The feedback I received from my students is that their O-level teachers told them that some of this knowledge is beyond the current syllabus and it would be imparted to them in the A-level. However, once the students hit the A levels, they received a rude wake-up calls because their tutors said the exact opposite and expect those fundamentals to be taught in the O-level instead! Suddenly, we have a catch-22 situation! In this article, I am not going to lament on the flawed education system because no system is perfect. Instead, I am going to identify some potential barriers to Chemistry learning based on my personal experience and views and it is not an exhaustive list. I would probably add more to this current list in the future.
Many of the concepts studied in Chemistry are abstract and are inexplicable without the use of analogies or models. For example, how do you distinguish between an element and a compound? What is the difference between an atom and a molecule? Is hydrogen gas an element or a compound? I have heard stories of teachers teaching their students the wrong thing i.e. a hydrogen gas is a compound because there are 2 atoms! Goodness, gracious! In school, we are taught that an element cannot be decomposed by chemical means whereas a compound can. However, the activity used to make the distinction is queer as it involves heating substances such as salt, water, sugar and yellow sulphur with a Bunsen burner. If we were to heat a table salt, there would not be any visible change but the water would boil away. According to the students’ observations, both sugar and sulphur would burn. Yet, we know that sugar is a compound and sulphur is an element and so how is it that the observation is identical for both substances based on the students’ perspectives? This example tells us that the distinction between elements and compounds cannot be easily made from this simple activity without resorting to explanations using molecular models representing compounds and elements.
Another common misconception exists between physical and chemical change. Many students claimed that physical change is a reversible process and a chemical change isn’t. Why? Because we can convert solid ice to liquid water and gaseous water vapour easily and vice versa. However, we can’t do the same to compounds such as sodium chloride salt. The appropriate response, that chemical change results in the formation of new substances with different characteristic properties, was never mentioned. To complicate the matters more, Chemistry can be represented on the macroscopic and microscopic levels symbolically through the use of chemical symbols, chemical formula and chemical equations. Furthermore, the students can’t see the connections between these symbols and the periodic table. If you can’t even write the proper chemical formula of a substance, you can’t write the proper chemical equation. Without a proper chemical equation, you can’t identify the exact type as well as the number of bonds formed and broken and you can’t calculate the enthalpy of a reaction. In Physics and Mathematics, you can isolate the topics and apply the relevant formulas but you can’t do that in Chemistry because everything is all interconnected and that is what makes Chemistry so complicated for students. Unfortunately, most of the Chemistry instruction occurs predominantly on the most abstract level, the symbolic level. Therefore to understand the microscopic levels (what is a proton, electron and neutron etc?), students must be capable of associating particles with models or analogies. However, the unresolved question is the age level at which molecular models are understood by students and the type of instructions which might make them meaningful because I have seen many students having difficulties relating analogies and models to chemical phenomena even at the tertiary level!
The next part concerns electrochemistry. In the O-level syllabus, the electrolysis of aqueous sodium chloride produces hydrogen and oxygen as the products. The students are taught to identify the ions present in aqueous sodium chloride, namely the hydrogen ions, hydroxide ions, sodium ions and the chloride ions. Hydrogen ions are reduced at the cathode to form hydrogen gas whereas hydroxide ions are oxidised at the anode to form oxygen gas. However, once the students go to A level, they realise it is not true because the concentration of hydrogen and hydroxide ions is only 10 to the power of negative seven. The concentration is so diluted that it is hard to believe that they would be discharged to form the respective products without any divine intervention! My take on this matter is that if we want to learn a concept, let’s do it once and make sure that we are learning everything correctly. Sometimes, it is very difficult to undo a student’s misconceptions once it is ingrained in them. As the saying goes, ‘old habits die hard’ and I think the same applies to learn. Nevertheless, there are always 2 sides to a coin. Perhaps the current education system is trying to teach us the ultimate truth about education which is to learn, relearn and unlearn everything all over again!
It is very unfortunate that students more often than not fail to integrate their knowledge and this leads to a fragmented view of Chemistry with many puzzling parts that do not seem to fit together. Therefore, it is the teacher’s responsibility to help the students improve their conceptual understanding and an opportunity for doing this is through practical works, which is sadly a wasted opportunity in some schools.