What is everything made up of?
What will its properties be?
What happens when you add this to that?
Now is this chemistry?
And as every journey needs a guide,
we all have one here as well.
A teacher who makes us think differently,
out of the nutshell.
For every single question we ask,
she will always explain.
Or search and show it to us in time,
come hail, snow, or rain.
I thought it prudent to start off with a poem penned by one of my students, Aishwarya, who is now studying at IIT, Chennai. Poems such as these, apart from giving me immense pleasure, highlight one vital aspect of teaching: the importance of inspiring students to think out of the box and kindling their creativity.
For the last 23 years of my teaching career, I have ensured that all my students appreciate the vital role that chemistry plays in their lives. Every activity such as brushing teeth, playing games on laptops and wearing fashionable clothes is governed by the laws of chemistry. Toothpaste has sodium fluoride, saccharine, and hydrated silica which scours any bacterial residue off the teeth. The same compound, silica gel or hydrated silica, is used in cameras and laptop packs to absorb moisture. Soaps contain long chain fatty acids which are surfactants and reduce the surface tension of water. People usually prefer clothes made from synthetic fibres for convenience and elegance. Synthetic fibres like terylene are the condensation polymers of terephthalic acid and ethylene glycol. It is not farfetched to declare that we are living in the “Carbon Age”. Wars continue to be fought over petroleum, which is primarily a complex mixture of hydrocarbons. The significance of organic chemistry cannot be over emphasized as carbon is an integral part of our lives.
What is chemistry?
In order to teach chemistry, one has to understand its origins. In the earlier days, there was a widely popular notion that any inexpensive metal could be converted into precious gold. Although alchemists could not achieve what they set out to, this era laid the foundation for modern chemists. Thus, it can be safely proclaimed that chemistry is the art of making substances change or watching their spontaneous transformations.
When we introduce different branches of science in class VI, the curriculum begins with symbols and formulae. These symbols and formulae fail to interest a child as she or he finds them meaningless and arbitrary.
In class VII, chemical equations are introduced and students start disliking the subject thanks to the mechanical pedagogy. The role of a chemistry teacher at this juncture is so vital that it can influence career decisions that these children make ten years later.
Here are a few techniques that I have employed to bring specific changes and make chemistry seem more interesting:
- By taking the students to a chemical factory where chemistry is in action.
- By performing chemical reactions that involve colour changes. Younger children find this particularly fascinating.
- Citing more applications of chemistry in everyday life.
- Laboratory methods of preparation of various gases like hydrogen, nitrogen, carbon dioxide, etc.
However, it is imperative that a teacher be well prepared before any practical session. She should rehearse the experiments beforehand and prepare worksheets that help evaluate the learning outcomes.
Passion is contagious. In order to make the students more inquisitive, the teacher must love the subject and possess vast knowledge. It is as important for the teacher to read as it is for her students. Students find a teacher who is cognizant and conversant with new research very inspiring. Objectivity and ability to answer questions of different types are useful assets too.
Methods to teach chemistry
Imagination: Making students imagine and picturize some of the concepts is an effective way to drive a point home. For example, when I teach the relationship between Gibbs free energy and randomness, I ask the students to imagine a big hydrogen balloon. I go on to ask: What will happen if a burning matchstick is brought close to the balloon? The immediate answer is: the gas will catch fire. What happens to the molecules of hydrogen inside the balloon? The molecules move out of the balloon and spread over a large area, increasing the randomness. Thus, the entropy of the system, comprising the balloon and the hydrogen molecules, increases. What happens to change in the enthalpy? Heat is given out by the system and the surroundings absorb this heat. Enthalpy of the surroundings will be positive while the system will have a negative enthalpy. This helps us derive the relationship between Gibbs free energy and the heat absorbed.
To calculate the number of atoms in a crystal, I ask the students to visualize a cube and its diagonals. This lays a strong foundation for me to calculate the number of atoms in a unit cell (which is cube shaped). The students understand the topic clearly and often come up with brilliant answers. Such methods serve the twin purpose of teaching a concept and kindling a student’s creativity.
A teacher must use effective questioning techniques in order to help the pupils vividly picturize a concept. Effective learning takes place when a topic is introduced by throwing open-ended questions to the entire class. This increases class engagement and tests the existing knowledge of the learners. Spontaneous questions can be framed based on students’ responses.
Fragmentation of a macro concept into smaller concepts
A concept can be better understood if it is broken down into smaller concepts and explained on the basis of cause-effect relationship.
Understanding chemistry entails a sub-microscopic approach where the concepts are elucidated based on the behaviour of molecules, atoms, and electrons. Explanation and logical reasoning at every level enhances appreciation for the subject.
To quote an example, the formation of coloured ions by transition metals is because of the excitation of electrons from one set of D orbitals to another set. This concept can be further subdivided into various smaller concepts such as:
Why is copper sulphate blue in colour?
Why is copper ammonia complex deep blue in colour whereas copper chloride is green in colour (note that all these compounds contain Cu 2+ ions)?
The argument can be extended to other transition metal ions such as Ni, Co, Fe, etc.
In order to explain cathodic protection, students can be asked to imagine a house made of iron. The rusting of the house can be prevented by electrically connecting the house to magnesium. Magnesium gets corroded and the iron house is saved.
Practice and repetition:
Sometimes, teachers have to rely on the benefits of age-old teaching concepts such as practice and assignments. Students in higher classes struggle to learn the mechanisms of organic chemistry because of the sheer complexity of the subject.
The human brain is an adroit recognizer of repeating patterns. I design worksheets to help them identify the basic pattern of the mechanisms, thus harnessing this incredible quality of the human brain. These assignments are formulated to help them gain more perspective on the logic behind chemical reactions. I also encourage the pupils to formulate the organic structures in their minds.
Metallurgical processes can be explained by showing short films on mining and extraction. This can be followed by a talk on environmental hazards of mining.
Teaching becomes easy and interesting when the teacher possesses a fair understanding of other basic sciences such as physics and biology. Osmosis can be explained best by describing vapour pressure – a concept from physics. Describing the relation between diverse topics will lead to a deeper and thorough understanding for both the teachers and the students.
Use of mnemonics
Various chemical reactions can be taught by composing musical tunes for the chemical equations.
The first 20 elements in the periodic table can be learnt HHeLiBeBCNOFNeNaMgAlSiPSClArKCa by creating a mnemonic using these letters, and this will help in information retention.
In an electrochemical cell, the left side electrode is represented as LOAN (left, oxidation, anode and negative) by combining the first letters. OMSGAPSA represents the first letters of dicarboxylic acids. (oxalic, malonic, succinic, glutaric, adipic etc.,) LEO – loss of electron is oxidation, GER – gain of electron is reduction.
The list can be extended to metal activity series also.
P to C – precipitate to colloid (peptisation)
C to P – colloid to Precipitate (coagulation)
The project method
Dialysis can be learnt by making students work with diabetic patients and preparing group presentations on the topic. Students can be asked to present a research report on drugs, such as cisplatin, used for cancer and how these drugs affect cancer cells. This will expose the pupils to the areas where chemistry is applied in the real world and will instil interest in them.
There is a tremendous demand for chemists in various fields such as material sciences, environmental science, pharmacy courses, etc., the list is endless. It is up to the teachers to inspire their students to take up professional courses to have a successful, fulfilling, and rewarding career.
I would like to conclude by quoting JD Lee the author of Concise Inorganic Chemistry book, a bible for the teachers “Large amounts of chemistry are quite easy, but some is enormously difficult. Master the parts that are not hard thoroughly, the rest will follow.”
Guidelines and recommendations for teaching of High School Chemistry – American Chemical Society
Chemistry Teaching – Royal School of Chemistry
The author is a passionate chemistry teacher working at Presidency School, Bengaluru. She can be reached at [email protected].