2 Students’ engagement and learning

An important purpose of any demonstration is to help students to learn. In Case Study 1, Mrs Rawool’s students learned about how different foods change when cooked, and it also helped them to develop their observation skills. Mrs Rawool used her skills in questioning to extend her students’ thinking. For example, she asked the student how they knew the rice would go white, rather than just accepting the student’s answer.

However, although demonstration may enable concepts and processes to be observed directly, you cannot assume that students will develop a scientific understanding from observation alone. As a teacher, you play a key role in helping your students understand and learn from a demonstration. Your role is as a mediator and interpreter (Monk and Osborne, 2000).

Students will not learn as passive observers; they need to be actively involved. Mrs Rawool did this by focusing the students on how the foods changed when cooked and encouraged the development of close observation skills by her questioning. She also related the topic to their experiences.

Another way to involve students is to give them a role or task to focus their observations. For example, older students could write down results and observations in their books as the demonstration proceeds.

One particular way of actively involving students in some demonstrations and encouraging them to think about what they observe is to use a technique described by White and Gunstone (1992) called Predict-Observe-Explain (POE):

  • Students predict what they think will happen and justify their prediction. There should be a reasonable basis for the prediction, rather than a guess. The prediction should require them to apply their existing knowledge and understanding to the situation in question.
  • Students observe and describe what they see happening.
  • Students are asked to explain their observation and try to reconcile any differences between their prediction and observation.

Using POE is a way of challenging their ideas, but can only be used when there is a basis for students’ predictions. This will give you a valuable insight into their understanding. Predictions based on guessing do not provide useful assessment information.

Pause for thought

The test for starch is a simple one that involves adding iodine solution to the food. If starch is not present, the iodine solution remains a yellow/orange colour. When starch is present, a blue/black colour is seen.

How could you use the POE technique to demonstrate this food test?

By using POE, you as the teacher are asking your students to apply their existing knowledge and understanding. Asking your students to justify their predictions allows you to find out what ideas the students already have. By asking students to observe what happens, you can assess and challenge their existing ideas. You will find out how one teacher, Mrs Mohanty, used POE in her demonstration of the starch test in Case Study 2.

Although students are likely to be familiar with different foods, they may find it difficult to make the link between the foods they eat and the nutrient groups. This is partly because things like ‘carbohydrate’, ‘vitamin’ or ‘starch’ are abstract concepts. You do not buy a bag of starch or eat a bowl of protein. The challenge in teaching this topic is to develop students’ conceptual understanding of the nutrient groups and how these are found in different foods. Confusion can easily arise from the imprecise use of terms such as ‘carbohydrate’, ‘starch’ and ‘sugar’. It is therefore important to make clear that sugar and starch are both carbohydrates, and when doing the food test for starch, use the term ‘starch’ rather than ‘carbohydrate’.

Case Study 2: Mrs Mohanty’s demonstration

In this case study, one teacher, Mrs Mohanty, describes her decisions when planning a demonstration she used when teaching food tests. Food tests may be difficult to carry out in class because of large class sizes or safety issues. Teacher demonstration is a useful strategy in these circumstances. The lesson was to 60 students in Class VI.

I wanted the students to learn that some foods contain starch and that the presence of starch in food can be detected through a simple test. I was worried that if every student was to carry out the test, a lot of food would be wasted. Also, there was not enough iodine. So I decided to use a demonstration to show them the test for starch in foods.

When I planned the demonstration, I decided to include foods with starch as well as foods without starch, to show the students the difference in the test result. I wanted to have lots of different foods to show them, so I needed a big space for the demonstration. In order that all students would be able to see, I decided to do the demonstration at floor level. Some students sat on the floor, some on chairs behind them and some stood at the back. I planned to have the less motivated students and those who found learning more difficult at the front, to give them the best chance of being involved. Also, to make sure that even those at the back could see, I decided to test foods on small plates rather than in test tubes, which are too small [Figure 1].

After explaining the test, I showed them the reaction of starch with iodine and then tested different foods. I wanted to capture the students’ interest, but this is not a very exciting food test. So I thought I would get the students to make predictions. After a few foods had been tested, I asked them to predict whether the test would be negative or positive, recording the show of hands for each category. This also told me whether students had understood the idea of starchy foods.

On the blackboard I drew a table with four columns for the results: the first column for the food type, the second for the original colour of the food, the third for the change in colour and the fourth for drawing a conclusion on the presence of starch [Figure 1]. I wrote the name of each food in the first column. I thought of asking a volunteer to write the results as each food was tested, but decided that students would be more involved if they wrote their own observations and inferences in their books.

Food type Original colour of the food Change in colour Is starch present?


Figure 1 A table to record the presence of starch in foods.

I was impressed by how interested all my students were and the thoughtful answers they gave. I noticed how they talked with each other about what was happening because they were sitting differently and able to talk more easily.

Pause for thought

  • What actions did Mrs Mohanty take that showed she was focused on the students’ needs and their learning?
  • How did her demonstration involve the students?
  • What do you think the students learned from the demonstration?

As you can see from Mrs Mohanty’s experience, planning and delivering a classroom demonstration while managing a large group of students is quite a complex teaching strategy. However, the fact that demonstrations can impact so positively on your students’ learning makes the effort really worthwhile.

1 Why use demonstrations?

3 Managing demonstrations