A topic in teaching science
This page has been prepared as pre-session material for a talk to be given for the Association of Chemistry Teachers of India.
On this page I present some extracts from diagnostic materials intended to help teachers explore their own students' thinking. The development of the materials was informed by research into the alternative conceptions ('misconceptions') found among a proportion of school students – often even after they have been taught about the scientific models set out in the curriculum.
The examples on this page are taken from materials freely available for use in schools and colleges provided by the Royal Society of Chemistry (RSC). There are links on this page to where you can find out more about the diagnostic materials and where to download them from the RSC website.
What would your students think – and why?
The task I am suggesting is to look at the examples below, and think about them as tasks you might set students of an appropriate age that you teach.
- How do you think your students would answer?
- Would they give responses well-aligned with chemical thinking?
- If they might give 'wrong' answers, what might influence their thinking?
Dissolving
- What will be the mass of the beaker and its contents when the sugar was added?
- What will be the mass of the beaker and its contents once the sugar was no longer visible?
- Do you think your students (especially early secondary age learners) will agree with you? If not,what might their thinking be?
Stability and reactivity
- Does the sodium atom spontaneously eject an electron?
- Would a sodium ion spontaneously 'capture' a free electron?
- Why?
- Do you think your students will agree with you? If not,what might their thinking be?
Chemical stability
The task here was to compare pairs of atoms/ions, and for each pair to ask whether one the species were of the same stability, or whether one species was more stable. There are seven sets of three species to compare. Here are some of the examples:
- Is there any difference in the inherent stability of these species?
- Do you think your students will agree with you? If not, what might their thinking be?
- Is there any difference in the inherent stability of these species?
- Do you think your students will agree with you? If not, what might their thinking be?
- Is there any difference in the inherent stability of these species?
- Do you think your students will agree with you? If not, what might their thinking be?
- Is there any difference in the inherent stability of these species?
- Do you think your students will agree with you? If not, what might their thinking be?
Why do reactions occur?
- Why does a chemical reaction occur between hydrogen and fluorine?
- Do you think your students will agree with you? If not, what might their thinking be?
Ionic bonding – true or false?
True or false:
- A sodium ion is only bonded to the chloride ion it donated its electron to.
- A sodium atom can only form one ionic bond, because it only has one electron in its outer shell to donate.
- The reason a bond is formed between chloride ions and sodium ions is because an electron has been transferred between them.
- In the diagram a chloride ion is attracted to one sodium ion by a bond and is attracted to other sodium ions just by forces.
- In the diagram each molecule of sodium chloride contains one sodium ion and one chloride ion.
- An ionic bond is the attraction between a positive ion and a negative ion.
- A positive ion can be bonded to any neighbouring negative ions, if it is close enough.
- It is not possible to point to where the ionic bonds are, unless you know which chloride ions accepted electrons from which sodium ions.
- A chloride ion is only bonded to the sodium ion it accepted an electron from.
- A chlorine atom can only form one ionic bond, because it can only accept one more electron into its outer shell.
- There is a bond between the ions in each molecule, but no bonds between the molecules.
Do you think your students will agree with you? If not, what might their thinking be?
Ionisation – true or false?
True or false:
- The atom will spontaneously lose an electron to become stable.
- Electrons do not fall into the nucleus as the force attracting the electrons towards the nucleus is balanced by the force repelling the nucleus from the electrons.
- Only one electron can be removed from the atom, as it then has a stable electronic configuration.
- If the outermost electron is removed from the atom it will not return because there will be a stable electronic configuration.
- The eleven protons in the nucleus give rise to a certain amount of attractive force that is available to be shared between the electrons.
- After the atom is ionised, it then requires more energy to remove a second electron because once the first electron is removed the remaining electrons receive an extra share of the attraction from the nucleus.
- After the atom is ionised, it then requires more energy to remove a second electron because the second electron experiences less shielding from the nucleus.
- After the atom is ionised, it then requires more energy to remove a second electron because the second electron is in a lower energy level.
- After the atom is ionised, it then requires more energy to remove a second electron because it experiences a greater core charge than the first.
- After the atom is ionised, it then requires more energy to remove a second electron because the second electron is nearer the nucleus.
- After the atom is ionised, it then requires more energy to remove a second electron because it would be removed from a positive species.
- The third ionisation energy is greater than the second as there are less electrons in the shell to share the attraction from the nucleus.
Do you think your students will agree with you? If not, what might their thinking be?
A teaching analogy?
Comparing the atom with the solar system (Taken from the RSC diagnostic assessment resource 'An analogy for the atom') {Taber, 2002}
- Which similarities and differences would you want your students to be aware of?
- Which similarities and differences might they suggest?
In the talk…
I intend to say a little about
- the nature of alternative conceptions (including the dimensions they vary along) and why they are important to the teacher;
- how students acquire alternative conceptions (particularly in chemistry where they learn about molecular level models and explanations that are not familiar from everyday experience)
- how teachers can detect and respond to their students' alternative conceptions
and will illustrate these general points with some discussion of examples of common alternative conceptions in chemistry (such as those that can be diagnosed with the resources I have referred to on this page).
Work cited:
- Taber, K. S. (2002). Chemical Misconceptions – Prevention, Diagnosis and Cure: Classroom resources (Vol. 2). London: Royal Society of Chemistry.
