Imagine you are new to learning chemistry. Which of the following explanations would better help you understand what an element is?
Explanation 1: An element is a material made up of just one type of atom.
Explanation 2: Gold is an element (point to it on the periodic table). Oxygen is an element (again, point to it on the periodic table). Carbon dioxide is not an element (point to both carbon and oxygen on the periodic table). An element is made up of just one type of atom.
A novice should find the second explanation easier to grasp. This is because a definition is an abstract thing. It summarises something we already know, but as students don’t know it yet, the definition is harder to make sense of. Leading with examples helps them understand the idea, so the definition acts as a summary of that idea.
Students learn in two ways: they can learn a quality or idea from a set of examples, and they can generalise this new idea beyond the examples. Being exposed to many examples of a particular concept gives students a fuller appreciation of a topic, but it’s also how they go about forming their understanding in the first place.
To teach in this way, we need example sets for each idea. To teach the concept of red, for example, we should show a huge group of varying objects demonstrating different shades of red, flagging each as being red. We must vary the object so students know that red isn’t an idea associated with one object alone. We would also include non-examples to show where the concept ends – things in shades of purple and orange that are not red, for example.
Here are some tips to help you effectively construct example sets.
1. Work with colleagues
Clarify the route by considering multiple views on the next logical example.
2. Be realistic
There’s no perfect set, so don’t try to create one. There will always be multiple excellent example sets for every idea.
3. Keep it simple
To begin with, just use the examples and try not to overteach by explaining every feature of them. Allow students to make the intended inferences.
4. Choose wisely
For example, He would be a poor first example for calculating the numbers of protons, electrons and neutrons since they are all 2 (even though the numbers are simple). Li would be a better example but is less concrete for students as they might not have heard of it, so you might think Al is even better.
5. Think like a student
Consider what incorrect inferences you could make from your illustrations. So, in the He example, a student’s first inference could be that they’re all the bottom number, which is wrong, so start somewhere different.
6. Use non-examples
You can use non-examples to reveal limits. This is especially relevant at the very boundary of an idea, such as adding a different atom into a pure substance makes it impure.
7. Check for understanding
Seek constant feedback via additional scenarios with the question sets to check students are making the correct inferences.
8. Mix up representations
This is particularly pertinent in chemistry. For example, when teaching mixtures, we don’t want students to infer that a mixture is ‘when the circles are different’. We must show mixtures as particle diagrams with circles, but also replace the circles with chemical formulas drawn out, spread throughout a beaker, and represented in as many other ways as possible.
Glean from prior knowledge to define whether students should start with examples or definitions. If they don’t have the relevant prior knowledge, definitions won’t make sense and examples will be the most efficient route to understanding. But if students do have prior knowledge, leading with a definition could be more efficient.