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The importance of images in chemistry
While there are many tangible chemical properties, the underlying reasons for these macroscopic properties can be abstract. Understanding requires a knowledge of what is going on at a level that is impossible to see with the naked eye. Subtle differences can meaningfully impact the properties of materials we use every day.
Why do we need images to teach chemistry?
Let’s look at some examples. Chlorine is a reactive, diatomic element which can be lethal if inhaled. One extra proton, one electron and four neutrons gives you neon - an inert, non-toxic monatomic element we breathe every day.
Even the same element can have different properties depending on how it bonds. Sodium metal is soft and reactive. In fact it reacts explosively with water. Remove one electron when it bonds with chlorine and you have table salt (NaCl). Now you can put it on your food or dissolve it in a glass of water.
One extra element can lead to large differences. Ethane (C₂H₆) is a gas at room temperature and is a by product of the refinement of crude oil. Ethanol (C₂H₆O) is a liquid at room temperature and forms through fermentation.
Even compounds with the same number of atoms of each element bonded in a slightly different way can have different properties. For example, R-limonene and S-limonene are almost identical. But R-limonene gives oranges their specific smell. While S-limonene smells like turpentine (with a hint of lemon).
The scale on which these interactions occur is as hard to grasp as the size of a supernova, or the seemingly limitless space between stars. Looking up at the night sky and trying to imagine the distance between us and the stars can be overwhelming. Similarly, thinking about the size of submicroscopic particles and their effects on macroscopic properties can be overwhelming.
To understand these changes it is important to be able to visualise what is happening. For this reason, images are essential to any comprehensive learning of chemistry.
Symbolic relationships, models and diagrams
One of the most important ways chemists represent submicroscopic entities is using symbolic relationships. That is, using letters and symbols to represents the elements present in a substance.
An equation like the one above describes what is happening in a reaction.
- The symbols show the elements present.
- The superscripts show the charges of the ions.
- The subscripts show the number of atoms of each element present in each substance.
- The number before each substance shows the ratio in which substances react.
Again, these are quite abstract concepts. The explosive reaction of hydrogen gas and oxygen gas to form water vapour is represented by:
Therefore, it is important that learners are exposed to more visual representations. One great method is building models of substances with their hands. They can use chemistry model kits, but jelly tots and toothpicks work just as well. It gives a three-dimensional representation of what is happening at the submicroscopic level.
For example, organic chemistry 3D model kits are very useful when thinking about how an alcohol and an acid react to form an ester.
In the classroom it is important to build models. And online it is important to give visual representations of what is going on at the submicroscopic level.
There are various types of visual representations that can be used in chemistry. They can make use of circles to represent atoms. They can combine both symbolic representations of elements with diagrams. And some attempt to show three dimensions on a two dimensional surface.
Electron geometry and molecular shape
In Grade 11, learners need to grapple with the idea that two molecules can have different molecular shapes but the same electron geometry. Or the same molecular shape and a different electron geometry! Diagrams are useful in showing how this is possible.For example, both silicon tetrachloride and phosphorus trichloride have a tetrahedral electron geometry. But silicon tetrachloride has a tetrahedral molecular shape, while phosphorus trichloride has a trigonal pyramidal molecular shape. This is because of the lone pair on the phosphorus central atom, but without diagrams this concept can be hard to grasp.
Submicroscopic diagrams to represent change
Submicroscopic diagrams can be used as an introduction to symbolic representations. Starting the year, Grade 10 learners might have little knowledge of using symbolic representations beyond the basic element symbols. By the middle of the year they would need to use them to represent chemical equations. So when talking about chemical and physical change it is unhelpful to give them only the chemical equation of a reaction.
Instead you can show them the reaction using submicroscopic diagrams.
White circles are hydrogen atoms, red circles are oxygen atoms. Both diatomic elements are shown in the gaseous phase. Two white circles and a red circle combined show water, also in its gaseous state.
These are the types of images and diagrams that we make use of to create meaningful, impactful learning experiences in our online, adaptive practice tool for Mathematics and Physical Sciences, Siyavula Practice.
Generating the actual diagrams
Siyavula Practice is not a bank of static questions. Rather, it contains generative question items. This means each question is actually an instance created from an exercise template. Each exercise template is built around one or more central concepts. But, the components, including images, quantities and scenarios, vary with each attempt of the exercise. We explain this further in our video on the technology components we have built.
So, an exercise on Siyavula Practice can contain more than just a static picture that asks a question. This possibility for variation means that the learner has to carefully read every question. Even on a second attempt of a similar question, generated from the same “template” as the previous question, they need to understand the question to answer it. Therefore, each of the diagrams mentioned above also need to vary to match the question and solution provided.
Submicroscopic diagrams can be used to show physical changes, including:
- phase changes such as melting.
- two substances mixing, but not reacting.
- an ionic compound dissolving in water.
They can also be used to show how the types of substances present changes in chemical reactions, including:
- a solid substance reacting with a gas to form a new, diatomic solid.
- a substitution reaction between a monatomic element and a diatomic compound.
We can encode this variation into our exercises, but it is important to make sure that all the diagrams generated adhere to the laws of Chemistry. Beyond that, it is important to make sure that the diagrams do not introduce any misconceptions or add to a learner’s confusion. As a result, making these sorts of diagrams requires time. But they are worth the effort!
These sorts of diagrams are so useful in understanding how chemical changes differ from physical changes or how specific physical or chemical changes occur. They also serve as a precursor to writing chemical equations and as a way to understand the conservation of atoms.
Check it out!
We will be adding more diagrams to our exercises going forward. If you would like to try out learning with the submicroscopic diagrams listed above, you can find them on our Siyavula Practice website! They live in the Grade 10 chapter Physical and chemical change. Get practising!
From social documentary through to high-end fashion, the history of England as told through photographs is as complex and divided as the nation itself.
A nation of pagans and punks, royalists and refugees, there is no single facet of life on the isle that cannot be disseminated through a thousand images. Here we celebrate the diversity of genres, photographers and peoples that have contributed to our image of modern-day England.
1. Richard Billingham – Untitled, from the Ray’s a Laugh series, 1995
Billingham, the pioneer of ‘squalid realism’ began shooting his seminal series Ray’s a Laugh when he was only 19. Originally, Billingham thought that he would use his pictures as studies for art school paintings, but didn’t finish any. Eventually his photos were discovered in his student room by a professor at his art college, who urged Billingham to submit them to galleries.
The series documents the lives of Ray and Liz, Billingham’s parents whom he called by their first names. It reveals the chaos which they were forced to live in as a result of Ray’s alcohol addiction. Billingham chose to shoot the images on the cheapest film he could find and used a harsh flash to add to the candidness of the series. Between the rawness and disarray, Billingham’s images still manage to show tenderness, and even joy. In 2001, Billingham was shortlisted for the Turner prize. Ray and Liz, in pictorial form, entered the photographic history books without ever leaving their small town of Cradley Heath.
2. Charlie Phillips – Notting Hill Couple, 1967
Charlie Phillips was given a Kodak brownie camera by a black American serviceman in his native Jamaica. After immigrating to London, England in 1956 he began to document life in his local community of Notting Hill, an area which had a large British Caribbean community following mass migration in the immediate post-war period.
This image was taken in 1967, a decade after a period of intense racial hostility in North London. In 1958 Notting Hill and the surrounding areas had been plagued by the eruption of violent and divisive attacks instigated by racist white youths. The events which later became known as the Notting Hill race riots began when a group of white men assaulted a white woman on the basis of her marriage to a black man. The disturbances, rioting and attacks continued every night for a week. Phillips’ beautiful image recalls the turbulence of the time, but hints towards a promising future, one of unity and acceptance.
3. Bruce Davidson – Girl Holding a Kitten, 1960
Bruce Davidson, who is known for his intimate photos of American youth also spent some time in England, cruising the streets in his cheap Hillman Minx convertible, with the top down. Davidson, who had always found teenagers intriguing, came across a London gang by accident one day when he was driving, and struck up a conversation. With his particular charisma, it didn’t take long for Davidson to be invited to come and dance with them at a dancehall. Davidson recalls that he had to move on quickly from place to place so only stayed with them for one night.
Of the group, Davidson picked out one girl, and took one of his most iconic shots. “There was a great deal of mystery to her. I didn’t know where she had come from, and I didn’t get her name, but there was something about that face – the hopefulness, positivity and openness to life – it was the new face of Britain.”
4. Martin Parr – New Brighton, From The Last Resort, 1983-85
One of the first British photographers to embrace the new trend in colour photography adopted by American photographers such as Stephen Shore and William Eggleston was Martin Parr. His series ‘The Last Resort’ has become both famous and infamous, acknowledged as one of the most quintessential representations of the British public, but likewise criticised for its portrayal of the working classes as uncouth and disorderly.
Yet, Parr claims it was not his intention to portray the people in his photos in a bad light. His entire career has been spent developing a new tone in documentary photography, projects that critically analyse modern life. He uses humour to understand his surroundings in an anthropological way. He is now represented by Magnum, much to the initial disdain of many other Magnum photographers at the time of his initiation. However, his work is now recognised as some of the most important in British photographic history.
5. Don McCullin – Children in Bradford, c. 1970
McCullin is famed for his images of conflict on the frontlines of international wars, but he also shot extensively in England. This poignant photograph speaks of times when tensions were high and the disenfranchised youth expressed their anger and feelings towards authorities of the era.
Important Images Of History
McCullin’s focus on the UK grew after studying the work of Billy Brandt, whom he idolised. Brandt photographed both the rich and poor, with equal respect. McCullin, who came from a working class background, found that he could relate more to those struggling under the Conservative government of the time, and turned his lens on the impoverished. This image speaks a thousand words; the faces of the children expressing fear, dissatisfaction, anger, rebellion and innocence all at once.
6. Julia Margaret Cameron – Untitled, 1863-1879
Photographing between the period of 1863 till her death in 1879, Julia Margaret Cameron was one of the most important and creative photographers of the 19th century, a true pioneer. Shooting prominent figures in the arts and sciences of her time, amongst them, Charles Darwin and Alfred, Lord Tennyson, Cameron is famous for her use of atmospheric lighting, soft focus and long exposure techniques.
Her work is immediately distinctive from her peers; trends in photography at the time were rigid and traditional, whilst she chose to portray her subjects in a more enigmatic and allegorical light. Cameron made her work on glass plates, the necessary long exposures resulting in her photos having spiritual and romantic qualities. Cameron claimed to have been inspired by scenes from religion and literature, and her hugely influential work is now recognised as having huge artistic significance.
7. Ian Bradshaw – Streaker Michael O’Brien is arrested at an international rugby match between England and France, 1974
Michael O’Brien started the trend of streaking at sports matches, a tradition that still, somehow, continues to this day. The Australian stock broker was dared £10 to run naked across the field at an England vs. France rugby game. In an extremely fortuitous moment, press photographer Ian Bradshaw managed to capture the instance policeman Bruce Perry covered O’Brien with his helmet. “It was a cold day and he didn’t have anything to be proud of, but I didn’t think twice about using my helmet.”
Bradshaw’s image shares a striking resemblance to a religious or renaissance painting, with the naked O’Brien playing the role of a persecuted Jesus. The photograph won numerous awards including the World Press Photo of the Year. It was also chosen as the “Picture of the Year” by the Life Magazine and “Picture of the Decade” by People magazine.
8. Tish Murtha – From Youth Unemployment, 1980s
In the times of mass factory and mine closures, Tish Murtha’s sharp social observation and lyrical sense of place drove her to depict the social dereliction that was sweeping certain areas of the nation in the hopes that her work could potentially be used help those being offered little political assistance.
Her series Youth Unemployment has become key in showing the social and economical division present during the times of Margaret Thatcher. Murtha’s photos are populated with friends, family and neighbours. Her strong personal ties to the subject matter compelled her to create work that could confront the reality and impact of political decision making of the day. In February 1981, Murtha’s work was raised as a subject for debate in the House of Commons.
9. Jane Bown – Samuel Beckett leaving the Royal Court Theatre, 1976
Jane Bown, who has worked as a staff photographer for the Observer for over six decades has worked in all areas of photojournalism covering everything from to catwalks to dog-shows. Bown was remarkably adept at understanding light, with certain reports citing that she could gauge the camera settings by checking how the light fell on the back of her hand rather than using a light meter. She also supposedly did little to no research on her subject before shooting them- giving her photos a fresh and non-judgemental air.
There had been no rapport between photographer and subject during Bown’s most famous portrait. Samuel Beckett, the intensely private Nobel Prize-winning playwright was described as “a mystery wrapped in an enigma.” For photographers, this made him an especially appealing subject. Bown, who had been sent by The Observer to get a portrait had initially been allowed to enter the Royal Court theatre on this pretence. However, at the last minute, Beckett changed his mind. As he tried to swiftly exit down an alleyway, Bown cornered him. Beckett, who initially tried to evade her lens, finally agreed to three shots but eventually stood still enough for her to expose five frames.
10. Edith Tudor-Hart – Gee Street, Finsbury, London, c. 1936
Edith Tudor-Hart (1908–73) has the most interesting story of all the photographers we have observed here. First, ‘Edith’ was her code name, and photography was not her true profession, but her hobby. A Viennese national, she had come to England to marry and remained there, but it soon became suspected – at least by covert government agencies – that she was a spy. As a secret service recruitment officer for the Soviet Union, she was a key figure behind the Cambridge spy ring at the height of the Cold War.
In a document declassified 50 years after it was written, it came to light that the British secret service MI5 subjected Tudor-Hart to round-the-clock surveillance, opened her mail, tapped her telephone, bugged her home and eavesdropped on the conversations of her friends and associates. However, it was the same qualities that made her a good agent – her unique ability to blend in, or disappear – that also made her such a great photographer. In this photo, although the subjects are aware of Tudor-Hart’s presence, we gain an insight into her background in espionage. By taking a candid shot from an upper-story building, Tudor-Hart reveals her empathy and solidarity with the British people.
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