1 Choosing when to do a demonstration
Where you have a choice, a demonstration may not always be the best approach to use to support your students’ learning. For example, students need to handle equipment in order to learn basic laboratory skills and techniques.
But in some cases a demonstration is the best option. Teachers often choose to use demonstrations rather than group practical activities because they:
- use only one set of specialist equipment for an activity
- may be quicker to do than organising the equivalent group practical activity
- give teachers greatest control, something that is especially important when a practical activity is complex or hazardous
- make it more likely that your students will see the correct procedure and results
- allow you to direct your students’ attention to things you want them to notice as you do the demonstration.
 Pause for thought
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Case Study 1: Miss Varsani plans when to use demonstrations in teaching ‘light’
Miss Varsani reviewed the practical activities related to reflection in the Class X textbook ‘light’ topic as part of her lesson planning.
I would like to include a range of practical approaches in my work with Class X, so I want to make sure that when I choose to do a demonstration it will be the most effective way of carrying out the activity. In making a decision about each practical, I took three issues into consideration:
- There are many students in Class X and I do not have much equipment.
- I have not done much group practical work before, and I am still a bit worried about control and safety issues when there are lots of students doing an activity at the same time.
- Whatever way I choose to plan an activity, my students must see the point of the activity quickly and not get distracted.
I drew up a table to help me decide where demonstrations would be most effective [Table 1].
| Activity | Key teaching points What do I want my students to learn? |
Demonstration or other type of practical activity? Key reason for choice? Comments? What else do I need to do? |
|---|---|---|
| 10.1 | Shiny spoon is like a convex mirror on one side and a concave mirror on the other side. Image in a concave mirror at different distances. Image in a convex mirror at different distances. Size of image? Erect or inverted? Real or virtual? |
Teacher-directed activity, but every student needs to try out the activity. Quickest and most effective if everyone has a shiny spoon. No changes with convex side, but everyone needs to see two types of image with the concave side. |
| 10.2 | Concave mirror converges rays of light from the Sun to a point. Very bright light at this point – energy delivered to one spot enough to cause damage or burning! Distance from mirror centre to point is roughly the focal length of the mirror. Conventions: Drawing curved mirrors and rays; rays from a distant object are parallel. Arrows are from object. Terminology: pole P, principal focus F, focal length f, principal axis, centre of curvature C. |
Demonstration. Safety: Potential hazard from bright light reflected into eyes, so I will do this. Draw the mirror, parallel rays from Sun and converging rays reflected from mirror to introduce drawing conventions and terminology. May be difficult to show that the image of the Sun is inverted! Leave to next activity? |
| 10.3 | Properties of images in a concave mirror for six different object positions. Position, size and nature of image. Using the terminology and conventions. |
Demonstration. Timing issue and ensures correct procedures and results. Quite lengthy and technical, so needs lots of questions and student involvement to keep attention. Different student ‘assistant’ for each situation. Issues about viewing images – everyone needs to see each image. |
| 10.4 | Ray diagram construction for each of six object positions from activity 10.3 to illustrate use of rules for constructing ray diagrams. | Demonstration. Timing issue and ensures correct procedures and results. Quite lengthy and technical, so needs lots of questions and student involvement to keep attention. Different student ‘assistant’ for each situation. Needs immediate follow-up by students drawing own diagrams. |
| 10.5 | Images in a concave mirror are always virtual, diminished and erect. | Teacher-directed activity with a convex mirrorfor each group. Enough mirrors for this so not resource issue. More effective and quicker for everyone to see this way. |
So, three of the six activities don’t present a resource issue and would be best done by my students, but the other three are still better done as demonstrations.
Pause for thought
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Activity 1: Planning your own teaching
This activity will help you to plan for teaching and learning about refraction as part of the Class X textbook chapters ‘Light’ and ‘The human eye and the colorful world’. You will need Resource 1 for this activity, or to make a copy of this in your notebook.
Look at the activities used for teaching and learning about refraction in the Class X textbook, Chapters 10 and 11. For each of them, make a note of:
- what you want students to learn from the activity
- whether you plan to do the activity as a demonstration or other type of practical activity. Give a reason for your choice: for example, resources, timing, motivation, safety, showing correct procedure and results.
Use the example in Case Study 1 above to help you complete the table in Resource 1.
How many of the activities in Chapter 10 would be best done as demonstrations? How many of the activities in Chapter 11 would be best done as demonstrations?
If there is another science teacher at your school, talk to them about how they make these decisions – and which demonstrations are they planning? To find out more, read Resource 2, 'Planning lessons'.
Why this approach is important